Feb 20

Gen 2 Volt Transmission Operating Modes Explained

 

By Jeff N, Patrick Groeneveld and George Bower

Preface

This article is based on a GM patent US 8,602,938, issued in December 2013, and presentations by GM at an SAE vehicle electrification conference on February 11, 2015 in Los Angeles. The presentations by GM verify that the patent described here is indeed used as the basis for the next generation “Voltec” transmission. This may be the first article to describe the design of the new transmission in detail.

Introduction
 

Slide1

The new 2nd generation Volt transmission is truly a work of art. It increases vehicle acceleration and efficiency while lowering cost, weight and size. The new Voltec system retains the EREV (Extended Range Electric Vehicle) design philosophy in which it operates as an electric vehicle without starting the gasoline range extender due to speed or acceleration as long as usable energy remain in the battery pack. How is this done and how does this new transmission operate?

The new transmission now has an integrated inverter eliminating heavy current conducting cables and the separate inverter assembly that was used in the original design. While the transmission offers increased efficiency and more flexible operating modes it does this without significantly increasing the parts count. The new transmission has the same number of clutches as the original. Extended range operation now has 3 modes and EV operation has 2 modes where the original transmission had 2 extended range modes and 2 EV modes.

The use of so-called rare earth metals (often imported from China) has been eliminated in the smaller motor (48 kW) and reduced by 40% in the bigger motor (87 kW). In EV driving, GM can now additively link the 2 motors together so the total power is actually higher than the original Volt which allows the 2016 Volt to accelerate from 0-30 mph in a very aggressive 2.6 seconds. The Tesla Model S60 reportedly does 0-30 mph in 2.5 seconds. Each motor contributes using different gear ratios to optimize its unique power and torque characteristics. The overall weight of the transmission system has been reduced by 100 pounds or 45 kg (27%).

GM’s new linked motor configuration provides for a wider torque band which is referred to as “torque spread” by GM engineer Tim Grewe in the video at minutes 1:50.

The new transmission has 5 operating modes which are shown in figure 2.

Slide2
5 operating modes listed
 
Detailed Description of Operating Modes
 

An overview of the new transmission is shown below. It shows 2 planetary gear sets where the original design used only 1. There are 3 clutches which are used to optimally reconfigure the power flow through the transmission at differ vehicle speeds and torque requirements (accelerator pedal position).

A simple planetary gear set consists of 3 geared components meshed together which have a fixed ratio to one another. A so-called Sun gear is in the middle and planetary gears connected to a common carrier plate rotate around it while also meshing with an outer ring with inward facing gear teeth.

Slide2

In the original Voltec transmission, the large motor (111 kW) was connected to the Sun gear, the gasoline range extender and smaller motor (55 kW) was connected to the ring gear, and the planetary carrier was connected to the output leading to the wheels.

The illustration below shows the new Voltec transmission in which the engine is connected to the ring of the first planetary gear set (PG1) and the smaller motor is connected to the Sun gear. The larger motor is connected to the Sun gear of the second planetary gear set (PG2). The two planetary gear sets are connected to each other and to the output to the wheels by the planetary carriers of each gear set. There are 3 clutches which are used to change the flow of power through the transmission.

When Clutch 1 is closed it mechanically links the PG1 Sun gear and its smaller motor to the ring gear of PG2. When clutch 2 is closed it mechanically links the ring gear of PG2 to the outer transmission case — it brakes or locks up the ring gear so it cannot move. The OWC or One-Way Clutch is a special clutch design which only allows rotation in one direction. The illustration below shows the approximate physical layout of these components in a cutaway image of the new Voltec transmission.

Slide3New 2016 Voltec
 
EV Operating Modes Description

The new transmission does most of its EV driving using the larger motor known as MGB, just like the original design. This motor is slightly smaller (87 kW vs 111 kW) than the original Voltec MGB but uses 40% less so-called rare earth metals. These metals allow increased torque density and help protect the permanent magnets in the motor from conditions such as high temperatures which would lead them to being demagnetized. The new MGB uses better manufacturing techniques which concentrates these reduced rare earth metals at the edges of the magnets segments where demagnetization is a concern.

Slide4
CD1: One Motor EV Mode

The new two-motor mode used for high torque output is shown next. This is a very simple operating mode to understand. Power is delivered straight to the wheels. However, as mentioned, each motor goes thru a different gear ratio resulting in a wider torque band. Note that in this mode the ring gears of the planetary gear sets are locked so the PG set is merely acting as a gear reduction.

Slide5
Two Motor EV Mode
 
Extended Range Operating Modes Description

Extended range, when the gas engine starts up, now has 3 modes instead of 2 in the original Voltec design. The new operating modes increase efficiency, especially in city driving. In 2 of the modes the motors can be dynamically “mixed” with the gas engine output in an eCVT or electrically continuously variable transmission mode. The 2 Modes where “mixing” is used are Low Extended Range and High Extended Range.

Low extended range is technically an “input split” style of eCVT. In this mode the large motor MGB is driving the vehicle through PG 2 to the wheels with the PG 2 ring gear locked together with the mechanical power from the gasoline engine on PG 1 and the electrical power generated by MGA on PG 1. By adjusting the power generated by and used by the two motors the engineers can put the ICE at its most efficient operating point.

This type of power splitting between the gas engine, the battery, and two electric motors was first developed by TRW around 1970 and its modern implementation was patented by GM in 1995 and by Toyota in 1997. It is used as the only mode in the Toyota and Ford hybrid transmissions and at lower city speeds and high torque conditions in the GM 2-mode hybrids. It replaces the less efficient “pure” series mode in the original Voltec transmission which was used at speeds under 35-40 mph and under high torque requirements.
Low Extended Range is shown below.

Slide6
CS1: Low Extended Range Mode
 
Fixed Ratio Extended Range mode is shown below. It can be used at moderate speeds and at moderate torque demand and allows the engine to directly drive the wheels with minimal electrical conversion losses.

Slide7
CS2: Fixed Ratio Extended Range
 
High extended range mode is shown below. In this mode neither motor is directly tied to engine speed or vehicle speed. This is technically known as a compound split mode and is similar but not identical to the output split mode of the original Voltec transmission where there was a more efficient mechanical path between the gas engine and the wheels at speeds over 35-40 mph with no more than light acceleration (torque demand).

Slide8
CS3: High Extended Range Mode
 
Conclusion

The new transmission is lighter and lower cost. Lower cost is achieved by using a smaller traction motor with fewer rare earth materials along with using an integrated inverter. Linking the 2 motors provides more torque and better acceleration than the first generation Voltec design. We may see this new transmission, or slightly modified variants of it, in other GM plugin and non-plugin hybrids in the future. It is hard to argue that this new transmission is anything other than a home run for GM.
More complete details will be released in a full GM technical paper to be published in April in conjunction with the SAE World Congress.

Hat tip to BillR for his contribution.

This entry was posted on Friday, February 20th, 2015 at 5:55 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

COMMENTS: 131


  1. 1
    Dave G

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    Feb 20th, 2015 (6:40 am)

    Great write-up.

    Question: In the pictures, what do the numbers after each mode mean?
    Mode CD1: (74)
    Mode CD2: (74)
    Mode CS1: (54)
    Mode CS2: (56)
    Mode CS3: (56)


  2. 2
    Dave G

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    Feb 20th, 2015 (6:52 am)

    Off topic:

    An interesting article about real world public charging statistics:
    http://www.greencarreports.com/news/1096885_some-electric-car-public-charging-stations-get-used-others-dont-why

    Here’s a snippet:

    …public chargers installed as part of the EV Project were utilized only four percent of the time, versus 42 percent for home-charging unit.

    The EV Project, which cost taxpayers about $100 million…


  3. 3
    James McQuaid

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    Feb 20th, 2015 (7:14 am)

    Great article gentlemen!

    We don’t get this type of excellence anywhere else. So-called main stream auto writers are much too busy driving ridiculously expensive old man’s sports cars, or otherwise wasting print bemoaning the death of the V-8 engine (simply because every car doesn’t contain a V-8), to learn anything new (much less report it).


  4. 4
    James

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    Feb 20th, 2015 (7:28 am)

    Any professional opinions about Volt2 being chain-driven vs. direct gear-driven in
    Volt1?

    I looked at the transaxle and wondered out loud if that was a weak point, or not
    vs. gen.1.

    Is that commonly done in automotive drive systems?


  5. 5
    Mark Z

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    Feb 20th, 2015 (7:39 am)

    Brilliant, absolute brilliant! Both the GM engineering of the new 2016 Volt transmission and your easy to understand graphics and text make for perfection of design and instruction. You all are to be congratulated for an excellent report on an important topic. Not only will the 2016 Volt be “fun to drive” as Tim Grewe mentioned, your detailed explanation is “fun to read”. Thanks guys for a great start to the weekend.


  6. 6
    KNS

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    Feb 20th, 2015 (7:43 am)

    Thank you gentlemen!!

    Anyone have any thoughts on what the impact of this new arrangement might be on the throttle lag sometimes experienced in the Gen 1 Volt?

    KNS


  7. 7
    James

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    Feb 20th, 2015 (7:49 am)

    Remember those little clear plastic small block V-8s you wanted for Christmas as
    a kid? Showing all the inner workings. I’d love to have a clear motor and gear case
    from Volt2 so I could spin it, shift to different modes, watching the clutches
    engage and disengage, just to wrap my head around which planetary is spinning
    when and watch it all mesh together.

    While I understand the basics and watch the GM graphic illustration video in motion,
    it’s too fast for me to totally wrap my head around exactly which is doing what, when.

    Even so – thanks for this depiction – it definitely helps to understand the drive process.


  8. 8
    James

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    Feb 20th, 2015 (7:55 am)

    Just like computers, cell phones and TVs – it’s fun to see how each new generation of
    power electronics, motors and transmissions get smaller and more efficient. Prius HSD
    units also get smaller and lighter with each new iteration.


  9. 9
    Loboc

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    Feb 20th, 2015 (7:57 am)

    Great job guys! It is fairly difficult to illustrate such a complex subject into a concise article.

    I hope GM does an automation of these modes like gen1. That was very helpful for my understanding.


  10. 10
    ziv

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    Feb 20th, 2015 (8:16 am)

    My 2013 Volt is pretty quick up to around 30 mph, but it sounds like the new one is going to fly off the line at stop lights. When you compare electric cars 0-30 times, the Volt is going to go from near the back of the pack to second only to the Tesla p85 with the 2016MY. That is kind of cool.

    The link is to Bro’s great comparo chart of the 0-30 times of various electric cars.

    http://gm-volt.com/forum/showthread.php?154409-Comparison-of-0-30-0-60-times-for-EVs


  11. 11
    James

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    Feb 20th, 2015 (8:31 am)

    Sports cars always hold a dear place in my heart. Seeing this newer, more compact
    configuration made my mind wander back to the Saturn Sky I saw the other day….

    Sad how the Sky and Pontiac Solstice just vanished so soon after they’d been born.
    Finally, after so many decades, in 2006 GM made not one, but two new 2 seat
    sports cars that someone not willing or able to buy a Corvette could enjoy. It sold
    as the Vauxhall VX Lightning in Europe, I believe. Could the Volt2 T-Pack be reversed
    with the T sitting between the front wheels, where the Solstice/Sky’s Ecotec turbo 4
    was located, and the Voltec drive unit be driving the rear wheels? With weight
    reduction, ratio changes and possibly a more powerful set of motors – with Tesla
    Roadster gone – this could be just the thing to light an enthusiast fire around the
    Volt technology.

    GM – Resurrect the Solstice and proclaim it – “THE VOLTA”!

    http://media.caranddriver.com/images/media/77503/2007-pontiac-solstice-gxp-saturn-sky-red-line-automatic-photo-77525-s-429×262.jpg

    I know this sounds stupid, but I’ve been struggling for 1/2 hour to post this photo and I give up! Sheesh – why did the post image button go away! I’ve tried img+brackets….bla bla….sigh

    Check out the huge center hump – perfect for the Volt battery pack to fit.

    http://images.dealerrevs.com/gallery/photo.php?id=58991198

    Rear drive BEV Volta Roadster – or even a FWD with T of pack in trunk, and v.2 Voltec EREV engine and motors up front – would be zippy, although a rear-drive sports car would be preferable.


  12. 12
    George S. Bower

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    Feb 20th, 2015 (8:45 am)

    James:

    While I understand the basics and watch the GM graphic illustration video in motion,
    it’s too fast for me to totally wrap my head around exactly which is doing what, when.

    I understand James. When people start talking PG sets and Mixing etc. peoples eyes gloss over.

    The thing to concentrate on is EV mode. GM has actually simplified EV mode. It’s all direct drive now. We are just driving either one motor or 2 motors straight to the wheels thru simple gear reductions.

    The trick thing is that in 2 motor EV we drive straight to the wheels thru DIFFERENT GEAR RATIOS. On gear ratio for each motor. This is very similar to the way Tesla runs the P85D dual motor.

    It gives a wider torque speed characteristic that Tim Grewe refers to as “spread” in the video.

    The Volt is an even better EV now than it was before, it’s lighter, lower cost and higher performance.

    There is no way anyone can argue against that…..although some will try and we must battle against them.


  13. 13
    Raymondjram

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    Feb 20th, 2015 (8:54 am)

    James:
    Just like computers, cell phones and TVs – it’s fun to see how each new generation of
    power electronics, motors and transmissions get smaller and more efficient. Prius HSD
    units also get smaller and lighter with each new iteration.

    So the next Prius model will be much smaller and need a shoehorn to get the driver and passengers in?

    Joking aside, this is an excellent article, Jeff and George! I have worked with simple transmissions as a hobby (amateaur mechanic), and even built one in a scale model powered with a small electric motor. So I am one of the few who isn’t a mechanical engineer but understands how this unit operates.

    As for the sprocket belt drive, my 1995 Buick Regal has a GM 4ET50-E (electronic control) 4-speed transaxle, and after 160,000 miles and twenty years, it has not failed or given any major problems (except a bad vacuum hose, fixed with a 60 cent replacement), not even a leak. Most GM transaxles have sproket chain drives and have not failed, either.

    GM manufactures some (or even most) of the best automatic transmissions in the world, such that Rolls-Royce used them and has a license to copy them. This new drive unit will give the Gen 2 Volt millions of miles of excellent service, and I see it being installed in future GM EREV models.

    Raymond


  14. 14
    Jeff N

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    Feb 20th, 2015 (8:59 am)

    Dave G,

    The numbers in parentheses refer to elements in the underlying patent. Follow the link to the patent and you will find those numbers. For instance, “36” is the patent label for the first planetary gear set. Feel free to ignore those numbers if you don’t have the patent in front of you.


  15. 15
    Jeff N

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    Feb 20th, 2015 (9:01 am)

    James,

    I believe it is common for transmissions to use chain drives like this and they are not associated with reliability problems.


  16. 16
    patrick

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    Feb 20th, 2015 (9:02 am)

    Dave G,

    The numbers between braces in the slides correspond to the figures in the GM patent that describes the transmission.


  17. 17
    George S. Bower

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    Feb 20th, 2015 (9:04 am)

    Raymondjram,

    I would think you would like what they have done to the motors as explained in the article. I believe Jeff N attended the motor presentation by GM as well….and Patrick has a PhD in EE.


  18. 18
    Jeff N

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    Feb 20th, 2015 (9:04 am)

    KNS,

    My understanding is that the new transmission will no longer have the 1-2 second “lag” that could sometimes occur in the original Volt when the car was using both motors and had to revert back to using only one motor becasue higher torque output was needed.


  19. 19
    Mark brooks

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    Feb 20th, 2015 (9:37 am)

    Very informative! Lower cost, better efficiency and better performance vs gen 1 , awesome! Now what about reliability? Meantime between part failure?
    One of the big sales pitches from nissan , tesla etc is that pure EVs have less moving parts to break and thus a dramatic increase in reliability.
    Are we really moving towards solid state cars, or is just a sales pitch?


  20. 20
    Neromanceres

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    Feb 20th, 2015 (9:44 am)

    Wow great job.

    To explain something so complex in such a short article and to do it very well is impressive. Technical writing at its best.


  21. 21
    Raymondjram

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    Feb 20th, 2015 (9:45 am)

    Mark brooks:
    Very informative! Lower cost, better efficiency and better performance vs gen 1 , awesome! Now what about reliability? Meantime between part failure?
    One of the big sales pitches from nissan , tesla etc is that pure EVs have less moving parts to break and thus a dramatic increase in reliability.
    Are we really moving towards solid state cars, or is just a sales pitch?

    As I posted above, GM transmissions have low rates of failure, and high reliability. I bet the Gen 2 Volt drive unit will last longer than any ICE transmission which runs at hotter temperatures and tend to wear down its clutches sooner.

    I doubt we will see a “solid state” car because we still need wheels on them! Maybe when levitation becomes possible (as in “Back to the Future”) then we will see cars with no wheels and no transmissions or “moving parts”.

    Raymond


  22. 22
    Raymondjram

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    Feb 20th, 2015 (10:07 am)

    A bit off-topic for today:

    Ex-GM CEO Dan Akerson comments about the Apple “iCar”:

    http://gmauthority.com/blog/2015/02/former-ceo-dan-akerson-has-a-few-words-of-caution-for-apple-car-executive-insights/

    http://www.detroitnews.com/story/business/autos/2015/02/18/apple-car-akerson/23603529/

    Raymond

    Edit: Here is more information about the Apple car:
    http://insideevs.com/apple-start-production-electric-titan-vehicle-2020-report/

    I am worried about this comment:
    “Foxconn declared their intent to produce electric vehicles last year, and now we are hearing credible rumors that Apple is as well- so it’s reasonable to assume this will be the builder for Apple.

    Who would have thought Apple will be what brings Chinese cars into the US market?”

    So Apple will bring a Chinese made EV?


  23. 23
    viking79

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    Feb 20th, 2015 (10:08 am)

    ziv:
    My 2013 Volt is pretty quick up to around 30 mph, but it sounds like the new one is going to fly off the line at stop lights. When you compare electric 0-30 times, the Volt is going to go from near the back of the pack to second only to the Tesla p85 with the 2016MY. That is kind of cool.

    Having test driven an i3, which feels insanely fast up to 30, I bet the new Volt will be a lot of fun to drive. You won’t win 1/4 mile drag races with it, but driving around town should be pretty enjoyable. Also, should you want to hypermill, that should be good at that too, using a smaller motor than Volt 1 should help efficiency here.

    Volt 2 looks like quite the extended range EV.


  24. 24
    DonC

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    Feb 20th, 2015 (10:18 am)

    Fantastic write up Jeff, Patrick, and George. Wonderful and clear explanation. LOVED the rid lines. Saved us all from going to LA and hearing the presentation! Nice job.

    While not a big issue at the moment. The reduction and elimination of the rare earth materials is a big deal. Big deal.


  25. 25
    Mark brooks

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    Feb 20th, 2015 (10:40 am)

    Raymondjram,

    Looking forward to the volt levitation option and never having to buy another snow tire!
    GM should just hire Dr. Emmett brown, and let him finish his flux capacitor design.

    Just a word of advice, don’t let that McFly side kick of his test drive the prototype!


  26. 26
    Raymondjram

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    Feb 20th, 2015 (10:48 am)

    Another off-topic article, but for the Ford Focus Electric with fast DC charging:
    http://insideevs.com/ford-focus-electric-dc-fast-charging/

    I wonder if Ford is serious about EVs since it only has one BEV and two PHEVs (Energi) models. If the newer Focus Electric does have the fast DC charge feature, maybe it will have a larger demand and compete better against the Nissan Leaf. We will see how the Chevy Bolt compete against both next year.

    Raymond


  27. 27
    ronr64

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    Feb 20th, 2015 (10:50 am)

    We must be missing some of the gears for the transmission as shown. Because if the ring gear is locked then the only way for a planetary gear to turn is to rotate around the sun gear. Yet it shows the wheels being coupled to the planetary gear… Connecting the wheels to either the ring gear or sun gear is fairly simple because they rotate around a single axis but how are they coupling the wheels to the planetary gear?


  28. 28
    Kent

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    Feb 20th, 2015 (10:53 am)

    Great article, but too technical for me. Can someone translate for me what this means when compared to Volt Gen I? What is the 0-30 for Gen I? What is the 0-60 for both Gen I & II?


  29. 29
    Patrick

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    Feb 20th, 2015 (10:59 am)

    ronr64: Connecting the wheels to either the ring gear or sun gear is fairly simple because they rotate around a single axis but how are they coupling the wheels to the planetary gear?

    I was initially wondering the same how the two sets of planets are connected to the wheel output. The GM slide presentation showed a cross section that shows how this is done. It is basically a set of 3 hollow shafts with bearings in-between, one over the other like those Russian dolls. Very ingenious.


  30. 30
    ronr64

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    Feb 20th, 2015 (11:09 am)

    Patrick,

    Yeah, I kind of already answered my own question. There must be a plate if you will that connects all 4 planetary gears together and the center of this is what is actually connected to the drive wheels. The exact how is not necessary for this simple explanation but it seemed impossible at first blush..


  31. 31
    Raymondjram

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    Feb 20th, 2015 (11:11 am)

    Patrick: I was initially wondering the same how the two sets of planets are connected to the wheel output. The GM slide presentation showed a cross section that shows how this is done. It is basically a set of 3 hollow shafts with bearings in-between, one over the other like those Russian dolls. Very ingenious.

    Due to those coaxial shafts, the output must be on a different shaft, and this is the need for the sproket chain drive to the differential and the two half axles toward the wheels (not shown in today’s article). The full SAE article shows these parts in the cutout image at the lower right:
    http://articles.sae.org/13666/

    Raymond


  32. 32
    Dave G

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    Feb 20th, 2015 (11:15 am)

    Mark brooks: GM should just hire Dr. Emmett brown, and let him finish his flux capacitor design.

    Plus Mr. Fusion to supply 1.21 gigawatts…
    https://www.youtube.com/watch?v=I5cYgRnfFDA


  33. 33
    Jeff N

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    Feb 20th, 2015 (11:20 am)

    ronr64,

    Right. The planet gears are also known as pinion gears and they are all attached to a plate called a planetary carrier.

    Here’s a short YouTube video that explains the basics of planetary gears:

    http://youtu.be/a1JAWoAvK-E


  34. 34
    Raymondjram

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    Feb 20th, 2015 (11:22 am)

    Dave G: Plus Mr. Fusion to supply 1.21 gigawatts…
    https://www.youtube.com/watch?v=I5cYgRnfFDA

    A gigawatt is a huge number! It is 1,000 megawatts, so I guess that the cabling can carry over one megavolt (MV) at over one kiloampere (kA) using large superconductor straps covered with at least 5 MV insulation.

    Science fiction becomes science fact when the physicists discover the reality of the concept. But it is up to us engineers to make it practical and economical to build. My experience with megawatt systems can be useful!

    Raymond


  35. 35
    stuart22

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    Feb 20th, 2015 (11:24 am)

    Goood work boys! Engineering art at its finest.

    If another Cadillac EREV was to be, it will need a higher level of performance than that of the Volt.

    Question – what modifications to this new transmission would achieve that? Bigger motors? More motors/clutches? Would a larger ICE be necessary, or could it all be done with hardware and programming revisions within the transmission and power electronic module?


  36. 36
    Noel Park

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    Feb 20th, 2015 (11:32 am)

    Raymondjram: “Foxconn declared their intent to produce electric vehicles last year, and now we are hearing credible rumors that Apple is as well- so it’s reasonable to assume this will be the builder for Apple.

    #22

    I was thinking that they might cut a deal with Warren Buffet and have BYD build them. I find this even more irritating, if that’s possible.

    +1 for good reporting, even if the news is gagging me.


  37. 37
    Jeff N

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    Feb 20th, 2015 (11:33 am)

    Kent,

    The original Volt goes 0-30 mph in around 3.1-3.4 seconds depending on who is doing the measuring. I think GM claimed 3.4 seconds back in 2011 but I’m not certain. The original Volt goes 0-60 mpg in about 9.0 seconds in EV and about 8.5 seconds with the gas engine on.

    The new 2016 Volt is said to go 0-30 mph in 2.6 seconds in EV and roughly about the same in hybrid mode with the gas engine running although they haven’t announced that number. The new Volt is said to go 0-60 mph in 8.4 seconds in EV and likewise roughly about the same in hybrid mode but no official number.


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    Noel Park

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    Feb 20th, 2015 (11:36 am)

    Neromanceres:
    Wow great job.

    To explain something so complex in such a short article and to do it very well is impressive.Technical writing at its best.

    #20

    Second the motion! +1


  39. 39
    Patrick

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    Feb 20th, 2015 (11:39 am)

    To explain the mechanical arrangement, look at the look GM’s cutaway picture in this article:http://articles.sae.org/13666/

    From right to left it is:

    ICE output + PG1 ring + OWC one-way clutch.
    Chain: to Wheel output shaft + PG1 planets (+PG2 planets) PG1 is invisible below the chain
    Center of MGB: outer shaft connecting PG1 planets to PG2 planets
    Then you see PG2 planets
    MGB rotor, connecting to PG2 sun
    Above that is Clutch 2, that connects between ground (top) and PG2 ring and to the left to Clutch2
    Then MGA, Its rotor connects via the inner shaft all the way back to the right to PG1 sun gear
    and finally Clutch 1, that is connected via an outer shaft to clutch 2 and PG2 ring on the left of it.

    The planetary gear at the right bottom is a fixed reduction gear connecting to the differential gear and front wheel shafts. Voltec-1 used conventional gears for that. So in total there are three planetary gears in Voltec-2, vs 1 in Voltec-1.


  40. 40
    Jeff N

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    Feb 20th, 2015 (11:42 am)

    stuart22,

    One thing GM emphasized in their presentation on the motors is that their manufacturing technique allows them to relatively easily tweak the winding count to increase or decrease the motor power.

    Because the new transmission has reasonably strong motors to take advantage of the Volt’s big battery power it may already be a reasonable choice to use in a car with a smaller battery but a larger gas engine — either a ~20 mile plugin hybrid similar to a Ford Fusion Energi or even a non-plug full hybrid. Or they could tweak the motors to better match a substantially larger gas engine. I think they have the ability to use this transmission design for cars other than the Volt (or ELR). It gives them flexibility to use it that way if the want to. I don’t think any other changes would be required.


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    hvacman

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    Feb 20th, 2015 (11:47 am)

    George,

    Great analysis. In the past, you have frequently opined that GM should go to a pure series hybrid configuration for the Voltec EREV drivetrain, eliminating the complexity/cost/weight of the PG set/clutches. This new drive train retains the clutches, adds a second PG set, and it even has true parallel hybrid modes to improve hybrid efficiency. What are your current thoughts on series vs mixed-mode hybrid?


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    Bone

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    Feb 20th, 2015 (11:48 am)

    In CD1 mode, the MGA must be freewheeling if there is no additional clutch to disengage it. Is this true?


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    Patrick

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    Feb 20th, 2015 (11:52 am)

    stuart22:
    Goood work boys!Engineering art at its finest.

    Question – what modifications to this new transmission would achieve that?Bigger motors?More motors/clutches?Would a larger ICE be necessary, or could it all be done with hardware and programming revisions within the transmission and power electronic module?

    To get significant more output would require careful upsizing of the ICE + MGB + MGA together, which essentially means a new tranny design. It seems possible to size this design up to fit larger cars like SUVs. This tranny’s sweet spot is an EREV, lets hope that GM plans to make larger plug-in cars. .

    Since tranny development is a major expense, that will be hard to justify for a niche car like the ELR. So I suspect that ELR-2 will again be a smoke-and-mirrors job with the exact same Voltec drivetrain. Just minor software tweaks and creative copywriting to eek out some better numbers.


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    Tim Hart

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    Feb 20th, 2015 (11:55 am)

    The Gen. 2 Volt sounds really great but I’m going to hold on to my 2012 Volt since we spent our money on a near new 2014 Spark EV. Gas free driving, except for trips, and tons of fun are on the way in one more week!


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    Patrick

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    Feb 20th, 2015 (11:55 am)

    Bone:
    In CD1 mode, the MGA must be freewheeling if there is no additional clutch to disengage it. Is this true?

    Correct. The one-way clutch on the ring and MGA on the sun are both freewheeling, which should result in only minimal drag.


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    FTLVolt

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    Feb 20th, 2015 (11:59 am)

    Kent,

    As much as I love the faster 0-30 in Gen II vs Gen I, one has to then think of the slower 30-60, since the overall 0-60 is not that much improved. In numbers:

    Speed – Gen I – Gen II
    0-30 – 3.2s – 2.6s
    30-60 – 5.6s – 5.8s
    0-60 – 8.8s – 8.4s

    Am I getting these numbers right?

    Is the new transmission design having to do with this change in speed ranges dynamics?


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    Einar

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    Feb 20th, 2015 (12:00 pm)

    Mark brooks,

    Yep – really want to see that Flux capacitor design finalized – then I could sleep in late and still make it to work at 5:00 am! LOL


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    Patrick

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    Feb 20th, 2015 (12:15 pm)

    FTLVolt:
    Kent,

    As much as I love the faster 0-30 in Gen II vs Gen I, one has to then think of the slower 30-60, since the overall 0-60 is not that much improved. In numbers:

    Speed – Gen I – Gen II
    0-30 – 3.2s – 2.6s
    30-60 – 5.6s – 5.8s
    0-60 – 8.8s – 8.4s

    Am I getting these numbers right?

    Is the new transmission design having to do with this change in speed ranges dynamics?

    The numbers are different in Electric mode in EV (CD) mode than in hybrid (CS) mode. I don’t know the acceleration numbers. Tim Grewe’s presentation presentation mentions that between 0-25MPH the acceleration G-force is 30% more than Volt 1 in CD mode, and 22% more in CS mode. Above 30MPH the acceleration is roughly similar to Volt-1.

    I think that the 30% extra g-forces to 25MOG will be very noticeable, and frankly its what I care most about as that is the city driving that I do most.

    This is all the result of engineering trade-offs: tuning for better acceleration comes at the expense of range and MPG(e).

    Note that Volt-1 was faster in CS mode than in CD mode, while in Volt two that seems to be reversed.


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    Jeff N

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    Feb 20th, 2015 (12:18 pm)

    FTLVolt,

    I’ve seen a graph which shows that acceleration is about the same above 40 mph between the old and new Volt. The new Volt blasts out of the gate from 0-25 mph and then ramps down and accelerates pretty much like the old Volt from around 40 mph up to its new top speed of 98 mph.


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    FTLVolt

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    Feb 20th, 2015 (12:33 pm)

    Patrick,

    To be clear, I am excited about the speedier “from stop” acceleration and surely understand the need for compromise. Yet, while a 98% city commuter, where 0-30 makes a difference, I never found the current Volt to be lacking in that regard.

    Personally, I would have been happier to see the improvement the other way around, in the so-called merging a highway scenario. Possibly due to my driving style or having a big hybrid Lexus sedan as a second car in the household, I find even the current gen car a bit lacking in the 30 to 75 sprint.


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    pjwood1

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    Feb 20th, 2015 (12:39 pm)

    Thanks guys. I was with others, on how you could possibly power wheels with a planetary gear, but it now makes more sense (hollow shaft). It would satisfy curiosity to have multiple tachometers showing where the drive is coming from, rather than a crude center stack animation.

    The nature of the EV beast – “fast hole shot, where did the power go?”. My Volt1 is nowhere near the ratio-effect felt by P85D, or MB B-class. I’d like to think higher battery storage flattens the torque curve, but when tapped in these cars, I think it just makes the initial punch that much more brutal. Volt2 sounds to me like it is reverting to nature. I’m not sure how, but always understood the potential low-end was electronically limited in Volt 1, anyway. As long as the previously anemic highway, two-motor mode gets better, I don’t think I was looking for much else. The bigger story is the range and efficiency these improvements bring.


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    Steve-o

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    Feb 20th, 2015 (12:39 pm)

    Bone:
    In CD1 mode, the MGA must be freewheeling if there is no additional clutch to disengage it. Is this true?

    Patrick: Correct. The one-way clutch on the ring and MGA on the sun are both freewheeling, which should result in only minimal drag.

    I still don’t understand. In CD1, the planetary carrier of PG2 is turning the planetary carrier of PG1, which turns both the crankshaft of the engine and the shaft of MGA (without causing MGA to generate any current), and all that is done with minimal resistance (and engine wear)? Is that the way it works?

    Also, in CS2, the only way for all the torque of the engine to go to the wheels is for power from the battery to hold MGB static?

    It seems like a lot of stuff is spinning freely, and the whole thing could use a few more clutches, but that is only because I don’t understand it, not because the design is wrong. Is there a clutch that can decouple the planetary carriers of PG1 and PG2? Probably not, because that would introduce a delay when acceleration is called for, spinning up MGB to close the clutch during CS2, but I’m still confused.


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    Streetlight

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    Feb 20th, 2015 (12:44 pm)

    Jeff N: My understanding is that the new transmission will no longer have the 1-2 second “lag”

    Jeff or George: Congrats to your team! Question: What is the drive voltage of each motor?

    One thing that struck me poking over the patent is that only two prior art citations are listed. That’s a wow.


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    larry4pyro

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    Feb 20th, 2015 (1:09 pm)

    I’m willing to bet this new transmission,even with its two motors is cheaper to manufacture than a standard automatic transmission. So I think it’s just a matter of time before we start seeing electric transmissions like the 5ET50 showing up in ordinary cars. What I mean is what if you keep the ICE and instead of the old 6-speed auto, you replace it with a cheaper to build electric transmission and a small battery. You then end up with a hybrid that drives like a Volt in CS modes, which is to say, it drives great, nothing like a Prius or other economic, and you get a significant increase in fuel economy.

    If you add a larger battery this vehicle now becomes a plug-in hybrid. It still uses the same transmission, but with a larger battery which increases costs but now allows all electric driving.

    What I’m wondering is can this transmission handle really powerful ICEs capable of producing 4-5 hundred horsepower? Would this produce the best of both worlds? Drive it easy and it gives great efficiency along with a smooth, powerful and quiet driving experience. Drive it hard and the beast of an ICE takes over supplemented with even more power from the electric motors. Is this what we will see in the Cadillac CT6 Plug-in and perhaps the future ELR?

    Finally, what happens if you take a plug-in hybrid and get rid of the ICE? Of course this then becomes a Battery EV, but would this new 5ET50 transmission be a better solution than a single large motor powering the wheels through a simple reduction gear? Certainly this propulsion system is simple, but it is a Jack of all trades when it comes to handling the torque demands in the different regimes of the performance envelope, being overly large for low torque situations and loosing efficiency at higher speeds. Wouldn’t a two motor system like that employed by the 5ET50 be a better solution? It more complex than the traditional setup but the higher costs could be offset by being able to use a smaller battery for a given range and by the economies of scale gained by using the same transmission for many different vehicles.


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    Feb 20th, 2015 (1:17 pm)

    Steve-o,

    In CD1 I think MGA will do the freewheeling on PG 1 because the engine is less willing to turn. Same story in the Toyota and Ford designs. It causes them trouble because there is an upper design limit on how fast MGA can spin. I think a modern Prius can spin their version of MGA at up to 13,500 rpm. The new Volt MGA can spin up to 11,000 rpm. In order to prevent damage at that point the Ford and Toyota designs have to send some power to MGA to resist spinning further which causes the engine to start turning. They can do that up to a point but at some rpm (not sure what it is) they will start up the engine so it turns and thus takes some of the rpm away from their version of MGA. The new Volt does not appear to exceed its MGA 11,000 rpm limit at 98 mph. Maybe different gearing ratios?

    In CS2, also known as Fixed Ratio Mode, there is no need to hold MGB. The gas engine drives the PG 1 ring gear and the Sun is being held by the clutch connecting it to the PG 2 ring which is being held by Clutch 2 to the transmission case. So, all of the power spins through the PG 1 planetary carrier. The PG 1 carrier is always connected to both the PG 2 carrier and to the wheels. So, MGB can just freewheel since the power is already going directly to the wheels. If it wants to, MGB can either help add some more power or can drain some off by regenerating into the battery,


  56. 56
    George S. Bower

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    Feb 20th, 2015 (1:22 pm)

    hvacman:
    George,

    Great analysis. In the past, you have frequently opined that GM should go to a pure series hybrid configuration for the Voltec EREV drivetrain, eliminating the complexity/cost/weight of the PG set/clutches. This new drive train retains the clutches, adds a second PG set, and it even has true parallel hybrid modes to improve hybrid efficiency. What are your current thoughts on series vs mixed-mode hybrid?

    The way GM did this says that the big cost drivers are in the motors not in shafts and gears and that makes sense to me. In a pure series arrangement you still need a huge traction motor and a generator (like gen 1 Volt and i3). This new set up allows GM to down size the traction motor and save dollars.


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    Feb 20th, 2015 (1:23 pm)

    FTLVolt:
    As much as I love the faster 0-30 in Gen II vs Gen I, one has to then think of the slower 30-60, since the overall 0-60 is not that much improved.

    According to the Autoblog article linked above,

    GM is not ready to publish acceleration times just yet, but the 2016 Volt has improved numbers, especially when going from 30-60 miles per hour.

    So, is acceleration improved for all speeds?


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    Noel Park

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    Feb 20th, 2015 (1:24 pm)

    Tim Hart:
    The Gen. 2 Volt sounds really great but I’m going to hold on to my 2012 Volt since we spent our money on a near new 2014 Spark EV. Gas free driving, except for trips, and tons of fun are on the way in one more week!

    #41

    Awesome. +1

    Saving the world one Volt and one Spark at a time. My hat is off to you.


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    Jeff N

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    Feb 20th, 2015 (1:24 pm)

    Streetlight,

    The motors are driven at roughly 350 volts which is around the battery pack average voltage level. There aren’t any DC-DC voltage bucking circuits like there are in the Toyota hybrids which have battery pack voltages a little over 200 but upconvert that to just over 600 in order to run the motors more efficiently. I don’t think Ford plays the same trick which may be why their efficiency is not as good at freeway speeds where that style of input-split power flow ends up generating a fair amountof power on MGA and then sending it over to drive MGB. The old and new Volt avoid the problem of the increasing electrical path at freeway speeds by not using input-split at those speeds. The old Volt uses output-split and the new Volt uses CD3 or compound-split and these allow more of the power to flow mechanically.


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    Noel Park

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    Feb 20th, 2015 (1:26 pm)

    FTLVolt: As much as I love the faster 0-30 in Gen II vs Gen I, one has to then think of the slower 30-60, since the overall 0-60 is not that much improved.

    #46

    Who cares? The few time I have ever matted the throttle I have felt terrible, as I knew that my AER was suffering. In my world the Volt is NOT about 0-60.


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    Noel Park

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    Feb 20th, 2015 (1:30 pm)

    pjwood1: The bigger story is the range and efficiency these improvements bring.

    #51

    I agree. That’s what the Volt is all about to me. +1


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    George S. Bower

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    Feb 20th, 2015 (1:33 pm)

    Noel Park: #46

    Who cares?The few time I have ever matted the throttle I have felt terrible,

    The few times I HAVEN’T I’ve felt bad. 🙂


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    Steve-o

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    Feb 20th, 2015 (1:33 pm)

    larry4pyro: What I’m wondering is can this transmission handle really powerful ICEs capable of producing 4-5 hundred horsepower?

    I think the power of the electric motors has to balance the power of the engine, or this transmission doesn’t work. That means a bigger engine requires bigger and more expensive electric motors, and bigger electric motors require a battery at least big enough to supply the power they demand, so I’m not sure this would still be cheaper than an automatic transmission for a large engine.


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    Jeff N

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    Feb 20th, 2015 (1:36 pm)

    larry4pyro,

    A lot of the performance in hybrid cards with downsized engines comes from the battery (obviously it has to come from somewhere). Smaller batteries typically can output less kW to drive the motors during acceleration. In order to have a powerful car with a small battery pack you need to rely more on the gas engine. Such a car with a 1.5 – 2.0 kW non-plug hybrid battery is not going feel like driving a Volt but with a good size gas engine it can still be fast. You could pobably match the 5ET50 with a larger engine that the 1.5L in the new Volt. It could probably handle a 2.0L well. Maybe even a little bigger but at some point you may need to upsize the motors and other aspects in order to take full advantage of, say, a 400 HP gas engine.

    The new Cadillac CT6 is supposed to have a plugin powertrain option. It’s probably going to be RWD like the other CT6 powertrains so it can’t literally use the 5ET50 but I wouldn’t be surprised if GM builds a RWD variant of the 5ET50 that is tuned for bigger engines that it can use on its other RWD vehicles.


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    Kent

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    Feb 20th, 2015 (1:44 pm)

    Noel Park: #46

    Who cares?The few time I have ever matted the throttle I have felt terrible, as I knew that my AER was suffering.In my world the Volt is NOT about 0-60.

    I hear you, but how I drive my Volt usually depends on how far I’m driving. If I know I’m going to run out of juice, then I drive conservatively to max out my range. However, if I’m only going on a 20 or so mile trip, then I might want to have a little fun with my Volt. JMHO, of course!


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    Feb 20th, 2015 (1:54 pm)

    Jeff N: In CD1 I think MGA will do the freewheeling on PG 1 because the engine is less willing to turn.

    Jeff N: In CS2, also known as Fixed Ratio Mode, there is no need to hold MGB. … So, MGB can just freewheel since the power is already going directly to the wheels. If it wants to, MGB can either help add some more power or can drain some off by regenerating into the battery

    OK, so I guess the part of the equation I have been overlooking is that the inverter determines whether a turning electric motor draws power from the battery or pushes power back into the battery, and at some point between, current doesn’t flow at all even though the motor is generating voltage? In that case were no current flows, the turning motor presents little resistance?

    I think the gen 1 power train was more about mechanical linkages, but this one requires more understanding of electric motors and inverters.

    I still wonder how MGB is held static in CS2 without damaging the motor, if that in fact ever happens. Does it always turn in CS2?


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    Feb 20th, 2015 (1:54 pm)

    Steve-o: I still don’t understand. In CD1, the planetary carrier of PG2 is turning the planetary carrier of PG1, which turns both the crankshaft of the engine and the shaft of MGA (without causing MGA to generate any current), and all that is done with minimal resistance (and engine wear)? Is that the way it works?

    Isn’t that what the one-way clutch is for? To keep the engine from spinning in either CD mode?


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    Jackson

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    Feb 20th, 2015 (1:56 pm)

    Off Topic:

    I went to my dealership this morning (baby’s first oil change at 20,000+ miles), and learned some interesting things. Based on what I’ve read here, I’ve been extremely lucky to find a very knowledgeable, motivated Volt dealership. Most of this, I learned from the service writer:

    A WARNING:
    Because Volt drivers change oil so infrequently, there is a tendency not to rotate tires often enough. This can greatly shorten their life (this sadly includes me. 🙁 ). The tires are designed for the Volt, so don’t think you can find cheap-os the same size somewhere else. They may physically mount on the rims, but won’t last long. Must be the extra weight + performance + efficiency.

    She first heard about the Bolt in October or November; proving that there was at least a source of information available for the rank-and-file. She confirmed that it will be released in all 50 States.

    AN ALERT FOR GM BEV ENTHUSIASTS IN ATLANTA:

    a3k2sk.jpg

    There is a used Spark EV on their lot. A dealership outside the release-limited area still cannot sell a new one, but this doesn’t apply to a used car:

    http://www.jimellis.com/certified/Chevrolet/2014-Chevrolet-Spark+EV-8bee33290a0a00e07a4702a6698c373c.htm

    Engine: Electric Drive Unit
    Transmission: AUTOMATIC
    Exterior Color: Summit White
    Interior Color: Electric Blue
    VIN: KL8CK6S02EC400065
    Model Code: 1CZ48
    Stock #: C0595
    Mileage: 5779

    They’re asking $16,900.

    Dawdling is not recommended.

    I spoke to Darral “D.P.” Porter, a sales representative at Jim Ellis Chevrolet in Chamblee, on PIB near I-285. darralp@jimellis.com

    jq14z8.jpg

    This dealership is the Volt headquarters of the SE, and they intend to carry the Bolt when it comes.

    2itt2q1.jpg

    These Volts are plugged in under a solar charger, the first of it’s kind in Georgia when it was installed.

    Does anyone know how/if tax credits apply to a used EV?


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    Streetlight

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    Feb 20th, 2015 (1:58 pm)

    Jeff N: There aren’t any DC-DC voltage bucking circuits like there are in the Toyota hybrids

    Thanks. The ‘938 distinguishes rare earth PM MG’s from induction motors as being larger to package. Doesn’t that indicate, as there’s one (1) each in tandem, each MG has its own drive electronics…I don’t see any sort of heat-sinking


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    Feb 20th, 2015 (2:09 pm)

    Jeff N:

    The new Cadillac CT6 is supposed to have a plugin powertrain option. It’s probably going to be RWD like the other CT6 powertrains so it can’t literally use the 5ET50 but I wouldn’t be surprised if GM builds a RWD variant of the 5ET50 that is tuned for bigger engines that it can use on its other RWD vehicles.

    I wonder if the 5ET50 confugration might also work in Silverado pick up truck. Yes we saw the 2 mode Silverado tranny not be a success but maybe this one would work. Perhaps GM could use this new formula as a “low cost” version of the old 2 mode.


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    Feb 20th, 2015 (2:20 pm)

    jsmay311: Isn’t that what the one-way clutch is for?To keep the engine from spinning in either CD mode?

    No. The one-way clutch is to prevent the engine from turning backwards. In CD1 mode, nothing would be trying to turn the engine backwards. In CD2 mode, the one-way clutch prevents the engine from turning backwards as MGA turns the sun gear.


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    Jeff N

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    Feb 20th, 2015 (2:43 pm)

    Streetlight: Thanks. The ’938 distinguishes rare earth PM MG’s from induction motors as being larger to package. Doesn’t that indicate, as there’s one (1) each in tandem, each MG has its own drive electronics…I don’t see any sort of heat-sinking

    The new MGA is still a PM motor, it just uses ferrite hard ceramic magnets now instead of ones made with rare earth metals. Ferrite magnets are used in starter motors but are not typically suited for use in PM motors like MGA. In order to make it work they had to innovate some new aspects of the magnet placement geometries and take other steps in the design and use of the motor to make sure they never stress it in ways that could cause it to demagnetize.they claimto have extensively tested it. Using rare earth metals helps to relax some of those parameters but they are more expensive and prices can be more volatile.


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    Feb 20th, 2015 (2:47 pm)

    Steve-o: No. The one-way clutch is to prevent the engine from turning backwards. In CD1 mode, nothing would be trying to turn the engine backwards. In CD2 mode, the one-way clutch prevents the engine from turning backwards as MGA turns the sun gear.

    OK. Yeah, you’re right. I think I had it backwards in my head.

    So, in that case, I think the engine would only spin foreward if the magnetic drag and friction in MGA overcame the static friction in the engine (through some gear ratio in the PG). I.e., the torque from the sun gear (from drag/friction from the unloaded spinning MGA) would have to exceed some threshold to overcome the static friction in the engine, driven through the ring gear.

    And this could be prevented fairly easily by routing just a little bit of power to MGA — just enough to match the RPM’s of the planetary gears, therefore reducing the torque on the ring gear.

    Does that sound right?


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    Steve-o

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    Feb 20th, 2015 (3:03 pm)

    jsmay311,

    Yes, that sounds right, and I see now that the ring gear is fixed in CS2, so MGB always turns. That answers my question here and here.

    This idea of electric motors turning without drawing or generating any power or resisting the torque or participating in any way is making my mind explode.


  75. 75
    jsmay311

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    Feb 20th, 2015 (3:10 pm)

    KNS: Anyone have any thoughts on what the impact of this new arrangement might be on the throttle lag sometimes experienced in the Gen 1 Volt?

    Jeff N: My understanding is that the new transmission will no longer have the 1-2 second “lag” that could sometimes occur in the original Volt when the car was using both motors and had to revert back to using only one motor becasue higher torque output was needed.

    I think this design will definitely eliminate the highway acceleration lag in while driving in CD/EV mode.

    But I’m not certain about how the Gen 2 Volt will behave when switching between the various CS modes.

    There was a thread on this same topic a few weeks ago. I just added a new post based on this new analysis: http://gm-volt.com/forum/showthread.php?156521-Acceleration-Lag-Gone-in-2016-Volt&p=2246249#post2246249

    That might be a good place to discuss it.


  76. 76
    Sean

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    Feb 20th, 2015 (3:22 pm)

    Guys normally I don’t skip when reading an article.

    But I found this too hard to understand.

    Jeff the next time you write something detailed like this could you simplify it in a way so that I can understand it and as well by showing how the technology works when it comes to drawings or computer animations of a vehicle would be a great example.

    Overall I don’t want to stop reading on gm-volt.com

    I just don’t understand complex stuff like this at all.

    But guys if you can break it up and simplify it for me that would be great!

    The Future Is Not Bio Fuel, Ethanol, Or Hydrogen, The Future Is Electric!


  77. 77
    Jeff N

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    Feb 20th, 2015 (3:39 pm)

    Sean,

    Perhaps GM will release a new animation of how it all works like they did for the first generation Volt.


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    SirSpammenot

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    Feb 20th, 2015 (4:00 pm)

    Dave G,

    CD = Charge Depleting.
    CS = Charge Sustaining.

    Depleting is using the battery only, while Sustaining is running the ICE to maintain a floating charge level (either during regular “empty battery” mode, Hold mode, or Mountain mode).

    FYI!


  79. 79
    George S. Bower

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    Feb 20th, 2015 (4:02 pm)

    James:

    While I understand the basics and watch the GM graphic illustration video in motion,
    it’s too fast for me to totally wrap my head around exactly which is doing what, when.

    Sean:

    Jeff the next time you write something detailed like this could you simplify it in a way so that I can understand it and as well by showing how the technology works when it comes to drawings or computer animations of a vehicle would be a great example.

    I’ll just repeat what I told James up top.

    The thing to concentrate on is EV mode. GM has actually simplified EV mode. It’s all direct drive now. We are just driving either one motor or 2 motors straight to the wheels thru simple gear reductions.

    The trick thing is that in 2 motor EV we drive straight to the wheels thru DIFFERENT GEAR RATIOS. One gear ratio for each motor. This is very similar to the way Tesla runs the P85D dual motor.

    It gives a wider torque speed characteristic that Tim Grewe refers to as “spread” in the video.

    The Volt is an even better EV now than it was before, it’s lighter, lower cost and higher performance.

    Don’t get too engrossed in the details of RE mode. While some think it is fascinating. Most do not and most don’t understand how a eCVT works so you are not alone.

    The simplest way for me to explain the eCVT in RE mode is that it allows the ICE to run at its most efficient operating points.


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    George S. Bower

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    Feb 20th, 2015 (4:14 pm)

    Jeff N: The new MGA is still a PM motor, it just uses ferrite hard ceramic magnets now instead of ones made with rare earth metals. Ferrite magnets are used in starter motors but are not typically suited for use in PM motors like MGA. In order to make it work they had to innovate some new aspects of the magnet placement geometries and take other steps in the design and use of the motor to make sure they never stress it in ways that could cause it to demagnetize.they claimto have extensively tested it. Using rare earth metals helps to relax some of those parameters but they are more expensive and prices can be more volatile.

    Jeff N,

    Raymondjram,

    Raymond, have you heard of this motor design?

    Jeff,
    Besides starter motors are there any motors in production using this design or is this new tech. or is this just something that has been bench tested for many cycles in the lab but not out in the field in production?

    Seems like this motor design might be a great way for GM to cost reduce the Silverado 2 mode. I thought that transmission was pretty trick but it got a lot of bad rap….partly because GM marketed it wrong but also because it was expensive. I still think it is just a matter of time until we see a hybrid tranny in all these p/u trucks along with all the latest weight reduction techniques.


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    kdawg

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    Feb 20th, 2015 (4:33 pm)

    Sean: Guys normally I don’t skip when reading an article.
    But I found this too hard to understand.
    Jeff the next time you write something detailed like this could you simplify it in a way so that I can understand it and as well by showing how the technology works when it comes to drawings or computer animations of a vehicle would be a great example.

    Sean, this diagram should explain how it works in a very simple manner. Let me know if you have any questions.

    circuit_diagram.png


  82. 82
    Mark Z

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    Feb 20th, 2015 (4:59 pm)

    Sean,

    Looking at the red arrow lines first gets the major idea across. The diagrams have the best detail for an overview of the action. The text adds detail after the diagrams seem clear. Wait a day and read it again for more revelation and understanding. It can take time, but the results are worth the effort.


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    larry4pyro

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    Feb 20th, 2015 (5:02 pm)

    Steve-o,

    I agree with your statement but the electric motors are already balancing the torque from the ICE which is greater than that generated by either or both of the motors. I’m not a ME so this stuff is new ground for me, but does this have anything to do with the lever diagrams mentioned in the patent. One thing they say is the lever has to be balanced by the torque at each node. The distance between nodes in the lever analogy is based on the gearing between the nodes, so I’m wondering if a small electric motor can provide the reaction torque required by a more powerful ICE. If so, how much more powerful of an ICE could this handle, or can the architecture simply be beefed up with more powerful motors to handle a more powerful ICE. I don’t pretend to know the answer, but I’m wondering if what we see in the Volt will show up in more mainstream cars, and even trucks.


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    George S. Bower

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    Feb 20th, 2015 (5:20 pm)

    Mark Z:
    Sean,

    Looking at the red arrow lines first gets the major idea across. The diagrams have the best detail for an overview of the action. The text adds detail after the diagrams seem clear. Wait a day and read it again for more revelation and understanding. It can take time, but the results are worth the effort.

    That’s right Mark Z.

    I’ve set as my goal to understand “compound split” by the time I die.


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    Noel Park

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    Feb 20th, 2015 (5:41 pm)

    George S. Bower: I still think it is just a matter of time until we see a hybrid tranny in all these p/u trucks along with all the latest weight reduction techniques.

    #80

    For sure. CAFE will make it happen. +1


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    Feb 20th, 2015 (5:43 pm)

    kdawg: Sean, this diagram should explain how it works in a very simple manner. Let me know if you have any questions.

    #81

    Oh yeah! I see it all now. +1


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    James

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    Feb 20th, 2015 (5:58 pm)

    Mark Z:
    Sean,

    Looking at the red arrow lines first gets the major idea across. The diagrams have the best detail for an overview of the action. The text adds detail after the diagrams seem clear. Wait a day and read it again for more revelation and understanding. It can take time, but the results are worth the effort.

    Motorcycle cop pulls driver over who’se on the wrong side of the road:

    Officer: “Didn’t you see the arrows?”

    Driver: “Why no, officer – I didn’t even see any Indians!”


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    Patrick

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    Feb 20th, 2015 (6:11 pm)

    larry4pyro:
    Steve-o,

    If so, how much more powerful of an ICE could this handle, or can the architecture simply be beefed up with more powerful motors to handle a more powerful ICE.I don’t pretend to know the answer, but I’m wondering if what we see in the Volt will show up in more mainstream cars, and even trucks.

    Any upscaling of this tranny requires a careful re-tuning of the relative sizes of MGA, MGB and the ICE. That is likely possible, but I’m not an automotive engineer to understand the the fine details of the trade-offs.


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    George S. Bower

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    Feb 20th, 2015 (6:51 pm)

    Noel Park: #81

    Oh yeah!I see it all now.+1

    That’s cuz you keep looking at the looking at the “Magic Smoke ” part 🙂


  90. 90
    Jeff N

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    Feb 20th, 2015 (6:55 pm)

    Jeff,
    Besides starter motors are there any motors in production using this design or is this new tech. or is this just something that has been bench tested for many cycles in the lab but not out in the field in production?

    Seems like this motor design might be a great way for GM to cost reduce the Silverado 2 mode. I thought that transmission was pretty trick but it got a lot of bad rap….partly because GM marketed it wrong but also because it was expensive. I still think it is just a matter of time until we see a hybrid tranny in all these p/u trucks along with all the latest weight reduction techniques.

    My impression is that the new ferrite-based MGA is somewhat novel and new tech to be used in an application like this. I recall seeing something about Toyota researching how to do this a year or two ago but we haven’t seen any results from them in a product yet,

    On the topic of the sales failure of GM’s SUV and pickup truck 2-mode hybrids, the failures were multiple in my opinion. Technically, I think the transmission was fine but it was too expensive because the volume of vehicles using the hybrid powertrain option was so small.

    From a customer outlook, the buyers of SUVs and trucks are often in politically conservative areas where hybrid tech is seen as environmentalist, liberal, and generally suspect. Chevy might have had better sales with a “coal roller” option that spread black smoke at the touch of a button than with a hybrid choice. Also, it was sold as a “performance hybrid” with towing capability and a full-sized V8 6L engine rather than as an mpg maximizing option where the electric motors allowed for the use oder a more efficient downsized fossil fuel engine.

    Toyota and Honda have also had poor sales when they built hybrid vehicles that had emphasized performance but turned in only modest mpg improvements.


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    Feb 20th, 2015 (6:57 pm)

    Patrick: Any upscaling of this tranny requires a careful re-tuning of the relative sizes of MGA, MGB and the ICE. That is likely possible, but I’m not an automotive engineer to understand the the fine details of the trade-offs.

    I think the 5ET50 concept would be a great idea in a Silverado…..all you do is scale it up. We did this all the time with gas turbines.

    The interesting thing is , in a way it trumps Via Motors design. In Via they use a pure series arrangement which seems cheaper at first but with GM’s new motor designs and the fact that the 2nd motor can be smaller it’s actually cheaper because as you said the motors are the big cost driver.


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    Noel Park

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    Feb 20th, 2015 (8:20 pm)

    James: Driver: “Why no, officer – I didn’t even see any Indians!”

    #87

    A guy gets lost in the forest. He remembers that firing 3 shots in the air is a signal that you need help, so he does.

    An hour goes by and nobody shows up so he fires 3 more.

    Another hour goes by and still nobody shows up. He says, “Boy I hope it works this time. I’ve only got 3 arrows left”.

    +1


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    Noel Park

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    Feb 20th, 2015 (8:22 pm)

    George S. Bower: That’s cuz you keep looking at the looking at the “Magic Smoke ” part

    #89

    Yeah, my eyes are sort of stinging and watering. At first I thought it was from squinting at your flow charts…………………….. +1


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    DonC

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    Feb 20th, 2015 (9:51 pm)

    kdawg: Sean, this diagram should explain how it works in a very simple manner.

    +20. Very funny. The twenty is because I had some people over and showed them your comment, and they all agreed you deserved “some points”.


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    Sean

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    Feb 20th, 2015 (10:51 pm)

    Guys I understand that patients is the key to understanding this stuff but I don’t understand complex math at all.

    If they showed an animation by slowly explaining how the generator, battery, gears and so fourth I probably would understand this stuff in someways.

    Like take for example look at this clip from Ford.com

    Look at the video that says The Heart Of It All.

    Though before The Ford Focus All Electric was released they had a longer detailed video that described the components of how the car worked when it comes to the technology of how this vehicle worked and I would like to see something similar but in more detail when it comes to the second generation Volt.

    http://www.ford.com/cars/focus/trim/electric/?fmccmp=lp-hybrids-top-hp-focus%20electric

    So I guess I’ll have to wait around May or June if GM releases something like that if they do such as like that cylinder magnet battery in computer 3D animation as an example just to say.

    The Future Is Not Bio Fuel, Ethanol, Or Hydrogen, The Future Is Electric!


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    Eco_Turbo

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    Feb 21st, 2015 (3:58 am)

    Only as a test of my understanding of the operation of the 5ET50… If MGA were replaced with another MGB sized motor, could the ice then be modified to increase it’s torque spread by adding a turbo charger?


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    Eco_Turbo

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    Feb 21st, 2015 (4:35 am)

    Since we’re talking about how things work, and Alessandro Volta’s birthday was last Wednesday, here’s an nice birthday salute to him:

    http://txchnologist.com/post/111388443285/happy-birthday-alessandro-volta-the-inventor-of


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    Dan Petit/Petit Technical College

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    Feb 21st, 2015 (8:43 am)

    People turn to many sources for information.
    However, the less they rely on the direct years of hard-won working experience, the more they hurt themselves.

    Search engines and aggregations of actions do not usually provide the best answers ever. They only provide expedient and slightly plausible WRONG answers, and ALWAYS INCOMPLETE answers.

    Take direct injection for example. Was there discussion about the valves no longer getting cooled and cleaned by the fuel spray? No.
    Was there discussion about needing to remove the cylinder head(s) every 80,000 miles to disassemble them to clean the valves? No.
    Was there discussion about the higher heat of the valve stem destroying the valve seals? No.
    How about excessively-long oil change intervals hardening those same seals so more oil leaks down? No.

    Yet since there was discussion all over the place that direct injection was “wanted”, that a consensus of no apparent implicit technical approval somehow took place within search engine analytics, and that the consensus would have all going well.
    The search engine-informed customer (AND tech) is never completely right.

    The more a shop uses search engines, the higher the repair bill is unnecessarily.
    The summer of 2011 which imposed 90 days of above 100 degree temperatures here in Austin TX impacted ALL internal combustion engines as if there were SEVEN summers’ worth of wear statistically, and the affects will continue to show up in shops all around central Texas.
    A second occurrence of such an event MIGHT finally awaken BEV naysayers when they get their overhaul bills for ICE’s or transmissions, that global heat is not their friend.

    The only 2 remedial solutions for motorists from these increasing financial assaults would be a good long range BEV, and, the very low ICE run-time of Volt.
    (You need to take charge of the oil change interval to have it done with only GM oil at least every year or the equivalent run time hours of 50 hours to prevent acidification-hardening of valve seals in my technical opinion.) (There are other unlisted reasons as well.)
    This is not asking too much for the purposes of prevention.

    Of course, people do begin to pay attention to words of experience when they begin to see signs of irregularity for themselves. Search engines set them up for distracted disregard and indifference because of the suddenness of displayed results, which tend to bypass and confound their practical filtering. Applied impracticality is assured if the search results repetitively display the same bad and non-contextual garbage. This includes aggregations of auto parts that are claimed to “fix” “a” “problem” [simplistically singularly-defined overall condition].

    Overworked medical pro’s sadly must use statistical aggregations due to excessive demands on them and the facility. (I will never accept computer-driven medical attention, EVER. The more that people accept that, the sicker they may become, and the shorter their lifespans.) (I humbly and sincerely advise that you had better slowly and carefully loose any excessive weight over the next year. Medical diagnostics are far easier for medical professionals if any excess weight has been slowly lost). (I lost 36 pounds and went from a 44″ to a 34″ over the last year with many pauses to learn how each 5 pounds lost increased my better health.
    Plus, your various systems are learning these things too. The biggest enemies are restaurants, which were/are allowed only several times a year).

    These long range BEV’s are coming very soon.
    One shop owner said to me last week; “That won’t affect me for ten years” as he contemptuously smirked.
    His problem is that his attitude is affecting him right now, though his willfulness blocks his acceptance of that fact.

    We are exponentially only five relationships away from knowing everyone else on the planet.

    This fact alone ought to be enough to maintain or instill proper business respect and thoughtful diagnostic due-diligence for one another’s vehicles, health, and futures.


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    Raymondjram

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    Feb 21st, 2015 (9:46 am)

    Sean:
    Guys I understand that patients is the key to understanding this stuff but I don’t understand complex math at all.

    It isn’t math, but mechanics that all this design is based on.

    For any vehicle that we need to move us or our cargo, we need a way to convert energy to movement (power the wheels for a certain distance), or as physicst call it: work. James Watt had to find a way to measure and compare his steam engine to the common workhorse, so he measured the work of a single horse. And he establish the unit that one horsepower is the work done by one horse to move 1,000 pounds one foot high (with a pulley) in one second.

    So we need to know mechanics to create a method of propulsion. The first self-propelled vehicles (now call an “automobile” or self-moving) were powered by steam engine in the 19th century. But at the same time the first electric motors were used to move small vehicles, limited by battery power. Now we have a mixture of gasoline, Diesel fuel, and compressed natural gas powered engines in present vehicles. The electric motor has returned with better battery chemistries to store more energy, and move our vehicles faster and longer (range).

    But most modern vehicles are hybrids (as the Chevy Volt), combining the electrical motor with the legacy gasoline engines, due to the lower energy capacity of the battery and the high energy capacity of gasoline. So we need mechanical engineers to combine both sources of power to the same wheels as a parallel hybrid, or use one (gasoline engine) to power the other (motor) in a series hybrid.

    GM has done a superb job with the new Gen2 Volt 5ET50 transaxle, combining the electric motors and transmission gearing in one package, now defined as an Electric Drive Unit (EDU). The only external inputs are electrical battery power, and the torque and horsepower of the gas engine through the physical attachment to the engine’s flywheel (a mechanical link). The external mechanical link will be to the wheels. It is more of a parallel hybrid than a series hybrid, and flexible enough to attach a different sized or powered engine.

    If this article was based on a true electrical car (now defined as a Battery Electric Vehicle or BEV) like the Spark EV, the transmission would be much simpler as there is only one source of power, and one single source of torque: the electric motor. Then the mecanical link would be only to the wheels.

    Raymond


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    Eco_Turbo

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    Feb 21st, 2015 (10:02 am)

    Dan Petit/Petit Technical College: Was there discussion about needing to remove the cylinder head(s) every 80,000 miles to disassemble them to clean the valves?

    Acording to Smokey Yunick, all you need to do is mix 1/3 kerosene, 1/3 transmission fluid, and 1/3 water in a coke bottle, shake it up and pour it down your intake at fast idle to clean your valves and intake. -Don’t tell SeaFoam-

    http://en.wikipedia.org/wiki/Smokey_Yunick


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    Eco_Turbo

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    Feb 21st, 2015 (11:05 am)

    Dan Petit/Petit Technical College: Take direct injection for example. Was there discussion about the valves no longer getting cooled and cleaned by the fuel spray?

    Chalk one up tp Chrysler, I’m sure their intention was to keep the valves clean: 😎

    25rl74z.jpg


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    volt11

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    Feb 21st, 2015 (12:22 pm)

    From Jeff: “it operates as an electric vehicle without starting the gasoline range extender due to speed or acceleration as long as usable energy remain in the battery pack.”

    One simple, highly informative sentence that GM has seemed utterly incapable of forming or otherwise conveying in its advertising. Nice.


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    Dan Petit/Petit Technical College

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    Feb 21st, 2015 (12:23 pm)

    Then buy the catalytic converters for $900 to $1600 or more.
    As I mentioned, answers are incomplete and wrong on the internet.
    Once a wrong answer is out here, someone somewhere gets the screw by doing the wrong thing to their own vehicle.
    The worst shop owner I met was one who got on the internet because he had a check engine light on with a code 420 for catalytic converter.
    He stated arrogantly that he found someone in England who had a Toyota Tundra just like his, who got the light off by pouring into the intake powdered (sic) laundry detergent.

    (But the light came back on for both converters with a 420 and a 430 instead.)
    He was blaming the Toyota dealer for “wanting to sell him two catalytic converters” [after he had done that].
    THESE ARE THE IDIOTIC THINGS DONE BECAUSE OF THE INTERNET.
    IT WILL ALL LIKELY GET WORSE.


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    Noel Park

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    Feb 21st, 2015 (12:28 pm)

    Raymondjram: GM has done a superb job with the new Gen2 Volt 5ET50 transaxle, combining the electric motors and transmission gearing in one package, now defined as an Electric Drive Unit (EDU).

    #99

    When you think about it, it is a pretty dazzling engineering achievement. +1

    For GM to invest that kind of effort to update what is arguably not that big selling of a car really shows a huge committment to the technology IMHO.

    George S. Bower: I think the 5ET50 concept would be a great idea in a Silverado…..all you do is scale it up. We did this all the time with gas turbines.

    #91

    And I think that the above just shows that something like what you are suggesting is pretty likely to happen. +1


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    Noel Park

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    Feb 21st, 2015 (12:30 pm)

    Eco_Turbo: Acording to Smokey Yunick, all you need to do is mix 1/3 kerosene, 1/3 transmission fluid, and 1/3 water in a coke bottle, shake it up and pour it down your intake at fast idle to clean your valves and intake. -Don’t tell SeaFoam-

    http://en.wikipedia.org/wiki/Smokey_Yunick

    #100

    If Smokey said it, I believe it. End of story. +1


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    Noel Park

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    Feb 21st, 2015 (12:32 pm)

    Dan Petit/Petit Technical College:
    Then buy the catalytic converters for $900 to $1600 or more.
    As I mentioned, answers are incomplete and wrong on the internet.

    #103

    Well yeah, there is that to think about. Smokey was a bit pre-catalytic, LOL. +1


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    George S. Bower

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    Feb 21st, 2015 (12:57 pm)

    Noel Park: #100

    If Smokey said it, I believe it.End of story.+1

    I remember reading Smokey’s columns. He was a regular on either Popular Mechanics or Mechanics illustrated…can’t remember which one though.

    I was going to tell Eco he’s dating himself with that comment.

    Eco_Turbo,

    Nice Hemi photo Eco.


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    Dave G

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    Feb 21st, 2015 (1:46 pm)

    For a range extender, my mind keeps wondering toward a BMW i8 type of solution.

    In the i8, the gas engine and electric motor are completely separate. The gas engine drives the rear wheels. The electric motor drives the front wheels.

    Since the i8 is a sports car, the gas engine is twice the size of the i3 and it has 2 turbo chargers. But its in roughly the same place, toward the rear of the vehicle.

    I keep wondering how this arrangement might work for a CUV or SUV plug-in. Unlike the i8, the majority of the power would come from the electric motor, so the gas engine could be smaller and simpler, allowing more room for rear storage. Maybe a small flat 4 or something.

    Thoughts?


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    Noel Park

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    Feb 21st, 2015 (1:56 pm)

    Dave G: Thoughts?

    #108

    I think that Porsche is doing something similar with the 918 and its current Le Mans prototypes. And I think that the Audis which have dominated Le mans for the past several years are similar as well.

    I have advocated for a similar configuration for the Corvette. Alas, My GM consulting contract appears to have been lost in the mail, LOL.

    In the past we have discussed making CUVs or SUVs AWD by adding electric drive on one axle, but I’m not sure that anyone has tried it yet.

    Seems like a good idea though. +1


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    Jim Simpson

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    Feb 21st, 2015 (2:05 pm)

    James,

    Chain drives in front wheel drive transmission have a pretty long history. There may be earlier examples, but the mid-60 Olds Toronado used a chain. In so far as I know, it was never a problem. I’m sure there it has a finite life, but probably more than long enough.


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    kdawg

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    Feb 21st, 2015 (6:06 pm)

    Just a crazy thought, but what if GM added another motor with another gear ratio? So 3 motors, and 3 planetary gears. I wonder if this would work for a truck application, for hauling heavy loads. A truck would have the room for a larger powertrain too.


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    kdawg

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    Feb 21st, 2015 (6:15 pm)

    Noel Park: In the past we have discussed making CUVs or SUVs AWD by adding electric drive on one axle, but I’m not sure that anyone has tried it yet.

    Protean has been doing it by putting the motors in the wheels. Here’s an article on a 2009 Ford F150 they converted.

    http://news.pickuptrucks.com/2011/05/driven-protean-ford-f-150-all-electric-pickup-truck.html

    6a00d83451b3c669e2015432426b93970c-800wi


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    George S. Bower

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    Feb 21st, 2015 (6:56 pm)

    kdawg:
    Just a crazy thought, but what if GM added another motor with another gear ratio?So 3 motors, and 3 planetary gears.I wonder if this would work for a truck application, for hauling heavy loads.A truck would have the room for a larger powertrain too.

    The 2 mode Silverado tranny had 3 PG sets and 2 motors and more fixed ratio gears. I think what GM did on the new Volt tranny is pretty profound from making more with less motor and as Patrick reminds me ….the motors are the big cost drivers not PG sets and clutches which are a dime a dozen…

    . IOW the new motor design sounds like the biggest influence coefficient.

    So this cost reduction idea can translate into bigger transmission also.

    I bet if you scaled this thing up and put in in a Silverado you could get 30 MPG out of it….then add a bigger battery and add a plug and you’ve got a winner….the motor design is what makes it.


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    George S. Bower

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    Feb 21st, 2015 (7:49 pm)

    Jeff N,

    Patrick,

    Did the Silverado 2 mode ever link motors in an additive fashion like the 5ET50?


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    jeffhre

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    Feb 21st, 2015 (7:54 pm)

    Mark brooks:
    Very informative! Lower cost, better efficiency and better performance vs gen 1 , awesome! Now what about reliability? Meantime between part failure?
    One of the big sales pitches from nissan , tesla etc is that pure EVs have less moving parts to break and thus a dramatic increase in reliability.
    Are we really moving towards solid state cars, or is just a sales pitch?

    We’re getting there from a basic design stand point. But pragmatically, ICE’s have the production engineering advantage of trillions of highway miles, and the collective experiences of thousands more models built, analysed and rebuilt. (Thank you Ellis)


  116. 116
    Dave G

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    Feb 22nd, 2015 (4:45 am)

    George S. Bower: as Patrick reminds me ….the motors are the big cost drivers not PG sets and clutches which are a dime a dozen…

    Induction motors are smaller, lighter, and cost less.

    And Tesla’s innovative firmware algorithms actually get higher average efficiency from induction.

    At first, this seems counter-intuitive. Conventional wisdom says permanent magnet motors are more efficient. But looking deeper, it becomes clear. PM motors have higher peak efficiency, but average efficiency may actually be less. For example, if you have a 150hp electric motor and you typically run it over 100hp, then PM is definitely more efficient. But if you typically run it around 25hp, then induction can actually be more efficient. Note that 25hp corresponds to driving 70 MPH on a flat road. 150hp is only used when you floor it.

    This is because the magnetic field on the rotor (the B field) is adjustable with induction motors. With a PM motor, the B field is fixed. At low power output, a large fixed B field works against you.

    But squeezing higher average efficiency from an induction motor isn’t easy. Modeling the induction motor to precisely control the B field in all situations is very complex. Tesla may have released their patents, but they haven’t released their source code. Without the source code, it would probably take years to perfect the firmware algorithms that make induction more efficient. Even with the source code, it would probably still take months to tune the firmware algorithm for a specific motor and vehicle.

    By contrast, the firmware algorithms that control PM motors are relatively simple, so that’s what most car makers use. But then they need complex gearing to try to get better efficiency from PM motors at lower output.

    More info here:
    http://www.teslamotors.com/blog/induction-versus-dc-brushless-motors

    snippet:

    In contrast, induction machines have no magnets and B fields are “adjustable,” since B is proportionate to V/f (voltage to frequency). This means that at light loads the inverter can reduce voltage such that magnetic losses are reduced and efficiency is maximized…

    Thus, induction drives may be the favored approach where high-performance is desired; peak efficiency will be a little less… but average efficiency may actually be better.

    … Induction machines are more difficult to control. The control laws are more complex and difficult to understand. Achieving stability over the entire torque-speed range and over temperature is more difficult with induction…


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    George S. Bower

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    Feb 22nd, 2015 (8:55 am)

    George S. Bower:
    Jeff N,

    Patrick,

    Did the Silverado 2 mode ever link motors in an additive fashion like the 5ET50?

    From looking at this link, it doesn’t appear to me that the Silverado 2 mode was able to additively link the 2 electric motors making the 5ET50 unique in that respect. On the other hand there was no real reason to link the motors since it was jus a hybrid not an EREV like the Volt.

    I’m wondering what the differences are in the motor designs between the 2 transmissions. I’m guessing that GM’s 5ET50 motor designs lend themselves to lower cost designs and that there application to a Silverado application would reduce costs significantly.


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    George S. Bower

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    Feb 22nd, 2015 (9:58 am)

    Dave G: Induction motors are smaller, lighter, and cost less.

    And Tesla’s innovative firmware algorithms actually get higher average efficiency from induction.

    At first, this seems counter-intuitive.Conventional wisdom says permanent magnet motors are more efficient.But looking deeper, it becomes clear.PM motors have higher peak efficiency, but average efficiency may actually be less.

    Interesting if true Dave. That would seem to validate both Telas and GM choices. Tesla only has one motor so it operates all over its map but GM has 2 motors and can force the motors to operate closer to their peak efficiencies.


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    Jeff N

     

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    Feb 22nd, 2015 (12:49 pm)

    Dave G: Induction motors are smaller, lighter, and cost less.

    I’m not an electric motor expert, but my impression is that only 1 out of 3 of those is generally true for AC induction motors versus rare earth permanent magnet (PM) motors.

    Induction motors generally cost less because the permanent magnets are typically made with relatively expensive rare earth metals. The 2nd generation Volt addresses that by building the smaller motor with Ferrite (Iron) magnets and GM made large reductions in the rare earth metals in the larger motor by using smarter manufacturing techniques to concentrate those metals at the corners and edges of the magnet segments where they are actually needed instead of mixing them evenly throughout the magnet.

    The references I read say that PM motors are generally lighter than induction motors for the same power. They are also pretty clearly smaller for the same power. They are more power-dense. Nothing in the article you linked to at Tesla disputes that or claims otherwise.

    Actually, that relatively old article (written when the Roadster was new) doesn’t say that induction motors would be superior in a Volt or similar plugin hybrid car. It just makes the case that AC induction motors with smart inverters can be as efficient (not more efficient) than PM motors overall when designed for high performance and large output capability as is needed in a sports car or for a 200-300 kW Model S.

    In particular, the Volt and other vehicles that package their motors inside the transmission case want the space efficiency of PM motors. This is less of a problem for a simple direct-drive EVs like the Roadster or Model S that don’t have to contend with needing an integrated eCVT transmission for a range extending engine.


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    Dave G

     

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    Feb 22nd, 2015 (2:16 pm)

    George S. Bower: Tesla only has one motor so it operates all over its map but GM has 2 motors and can force the motors to operate closer to their peak efficiencies.

    This leads me to ask the question: Why does the Volt have 2 electric motors?

    In a pure series design, a separate generator is required, but the Volt has gears that connect the gas engine to the wheels.

    If the engine is geared to the wheels, why couldn’t a single, more powerful induction electric drive unit act as both a motor and a generator, depending on current needs? This seems like it would cost and weigh less than GMs solution of using 2 PM motors.


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    Patrick

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    Feb 22nd, 2015 (2:29 pm)

    Dave G: This leads me to ask the question: Why does the Volt have 2 electric motors?

    Its because Volt has a eCVT when driving on gasoline. An eCVT always has 2 motors.


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    Dave G

     

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    Feb 22nd, 2015 (3:21 pm)

    Patrick: Its because Volt has a eCVT when driving on gasoline.

    Why does a range extended EV have to use a traditional continuously variable transmission?

    Tesla has shown us that a single powerful induction motor can save a lot of cost and weight, and it can even have higher average efficiency with innovative firmware in the inverter.

    In a range extended EV, if the gas engine is connected to the wheels, and a single induction electric drive unit is connected to the wheels, then the induction drive could act as either a traction motor or a generator, depending on current needs.


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    Raymondjram

     

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    Feb 22nd, 2015 (4:57 pm)

    Eco_Turbo: Acording to Smokey Yunick, all you need to do is mix 1/3 kerosene, 1/3 transmission fluid, and 1/3 water in a coke bottle, shake it up and pour it down your intake at fast idle to clean your valves and intake. -Don’t tell SeaFoam-

    http://en.wikipedia.org/wiki/Smokey_Yunick

    Most engines are using a direct type of fuel injection, so the intake valves never see the fuel mixture coming in. The older throttle body system used one injector in the intake manifold (replacing the carburator) and the ported system (one injector per cylinder ahead of the intake valve) actuall wet the intake valves. The direct system is cleaner. I have seen the intake valves in my 1995 Buick Regal’s 3.8 L V6 and after twenty years they are quite clean.

    No Yunick mixture needed! It all depends on how many times your engine runs rich, mostly due to colder temperatures. Here the coldest my engine ever sees is about 65 F in December.

    Raymond


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    Raymondjram

     

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    Feb 22nd, 2015 (5:07 pm)

    Raymondjram: Most engines are using a direct type of fuel injection (into the cylinder), so the intake valves never see the fuel mixture coming in. The older throttle body system that used one injector in the intake manifold (replacing the carburator) and the ported system (one injector per cylinder ahead of the intake valve) actuall wet the intake valves. The direct system is cleaner. I have seen the intake valves in my 1995 Buick Regal’s 3.8 L V6 and after twenty years they are quite clean.

    No Yunick mixture needed! It all depends on how many times your engine runs rich, mostly due to colder temperatures.

    Raymond


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    Jeff N

     

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    Feb 22nd, 2015 (6:15 pm)

    Dave G: Why does a range extended EV have to use a traditional continuously variable transmission?

    Tesla has shown us that a single powerful induction motor can save a lot of cost and weight, and it can even have higher average efficiency with innovative firmware in the inverter.

    In a range extended EV, if the gas engine is connected to the wheels, and a single induction electric drive unit is connected to the wheels, then the induction drive could act as either a traction motor or a generator, depending on current needs.

    Tesla didn’t show that a 100 kW induction motor would have higher average efficiency than a 100 kW PM motor. They said that a 200+ kW induction motor might have up to the same average efficiency as a 200+ kW PM motor. Part of their point was that average efficiency might not scale up equally between induction vs PM for the larger motor sizes in the high powered cars they were building.

    It isn’t at all clear that a gas engine + conventional transmission and an induction motor would be cheaper than a gas engine plus a 2 motor eCVT transmission with reduced rare earth metal usage.


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    Feb 22nd, 2015 (9:50 pm)

    Jeff N: It isn’t at all clear that a gas engine + conventional transmission and an induction motor would be cheaper than a gas engine plus a 2 motor eCVT transmission with reduced rare earth metal usage.

    With EVs, everything is new, so yes, the best solution is far for clear, but that doesn’t prevent us from speculating…

    From what I’ve read, the BMW i8 has only 1 electric motor.

    Does anyone happen to know whether the i8 uses PM or induction?

    As I said before, for a range extended CUV or SUV, I wonder how an i8 type of setup might work, except with more electric power and range, and less gas engine power. The 2-motor PM setup in the Volt seems like it would be expensive to scale up to an EREV CUV or SUV.


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    Feb 22nd, 2015 (10:21 pm)

    Jeff N: Part of their point was that average efficiency might not scale up equally between induction vs PM for the larger motor sizes in the high powered cars they were building.

    The Model 3 will be more of a family sedan, but I bet they still use induction. If the electric motor has a peak output of 150hp but the typical load is only 25hp, I suspect the average efficiency of an induction motor will be quite competitive. Induction will certainly be smaller, lighter, and less expensive than a PM solution.


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    kdawg

     

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    Feb 22nd, 2015 (10:43 pm)

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    Jeff N

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    Feb 22nd, 2015 (11:35 pm)

    Dave G: The Model 3 will be more of a family sedan, but I bet they still use induction.If the electric motor has a peak output of 150hp but the typical load is only 25hp, I suspect the average efficiency of an induction motor will be quite competitive.Induction will certainly be smaller, lighter, and less expensive than a PM solution.

    Tesla hasn’t said what form the Model 3 will take so we really don’t know. Since they make their own motors and their existing experience is with AC induction, I suspect you are right that they will stick with what they know.

    It’s pretty hard to find concise articles comparing AC induction vs. PM motors for automotive use other than the one you linked from Tesla. If you look at non-automotive sources then the following quote from a company that makes both AC induction and PM motors is typical:

    In short, permanent magnet AC motors are inherently more efficient due to elimination of rotor conductor losses, lower resistance winding and flatter efficiency curve. Due to their synchronous operation, PMAC motors also offer better dynamic performance and speed-control precision — a major benefit in high-inertia positioning applications. Although in some cases the system power factor with a drive may not be as high as a motor-only induction machine, PMAC motors generally provide higher power density due to higher magnetic flux. This means more torque can be produced in a given physical size, or equal torque produced in a smaller package. Finally, PMAC motors generally operate more coolly than AC induction motors, resulting in longer bearing and insulation life.
    Because a permanent-magnet rotor lacks conductors (rotor bars), there are no I2R losses — so everything else being equal, a PMAC motor is inherently more efficient.

    See pages 12-13 of:
    http://www.leeson.com/documents/Platinum%20e%20Supporting%20Documents/PMAC_Whitepaper.pdf


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    Jeff N

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    Feb 22nd, 2015 (11:58 pm)

    Dave G
    Does anyone happen to know whether the i8 uses PM or induction?

    Modified PM with reduced rare earth metals.

    Here’s a good article:

    http://www.greencarcongress.com/2013/08/bmw-20130812.html

    And here’s a detailed overview of BMW’s motor which they use in both the i8 and i3. Note, the acronym ASM presumably means an AC induction motor:

    http://hybridfordonscentrum.se/wp-content/uploads/2014/05/20140404_BMW.pdf

    The claimed 97% efficiency over a wide speed and torque range is very good.


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    Jeff N

     

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    Feb 24th, 2015 (1:58 pm)

    There is a new article up at GreenCarReports that covers the same topic but as a higher-level overview and includes a number additional nice I llustrations provided to them by GM:

    http://www.greencarreports.com/news/1096942_2016-chevrolet-volt-powertrain-how-it-works-in-electric-hybrid-modes