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Voltec drive unit has four basic modes of operation

72K views 81 replies 28 participants last post by  rjmcinnes 
#1 · (Edited)
I liked their description...because it breaks it down fairly simply info four modes...I was not trying to raise the controversy again and bring out the haters/trolls.

a) Industry recent news | Design News
Edit: WayBackMachine: Electronics Boost Chevy Volt's Efficiency - 2010-11-16 17:38:00 | Design News

Electronics Boost Chevy Volt's Efficiency - The Chevy Volt is more than a green vehicle. It's a smart, seamless driving machine that in some cases exceeds the performance of gas-burning cars.
Charles J. Murray, Senior Technical Editor, Electronics -- Design News, November 16, 2010

<snip>
Voltec drive unit now has four basic modes of operation: electric driving (low- and high-speed); and extended range driving (low- and high-speed).

Here's a quick look at the four modes as described in the article [] are additions:

Electric Low-Speed [in Charge-Depleting (CD) mode]: The simplest and most well-known of the Volt's four modes, this calls for the vehicle to use the charge from its 435-lb lithium-ion battery pack to power a 111-kW ac traction motor. When the traction motor turns, it transmits power to a sun gear in a planetary gear set, which turns the drive axle. Volt owners are expected to make heavy use of this mode - many will drive the car to work and back, charge it at night, and never use a drop of gasoline in the process.

Electric High-Speed [in Charge-Depleting (CD) mode]: The Volt typically hits this mode at about 70 mph. Then, the supervisory controller splits the power between the large traction motor and a smaller 54-kW generator-motor (which is still operated by the battery). The planetary gear set blends the power from the two motors and sends it to the drive axle. Even as it switches to this mode, however, the Volt still isn't employing its internal combustion engine - and therefore still isn't burning any gasoline.

Extended Range Low-Speed [in Charge-Sustaining (CS) mode]: When the battery's charge drops to an unacceptable level, the 1.4-â„“ I-4 engine makes its debut. At low speeds, the engine spins the generator-motor, which replenishes the battery.

Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split. It calls for power to be delivered through the big traction motor and through the smaller generator-motor. Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency."
<snip>
Sidebar:
So is it an EV? Or a hybrid? To be sure, there's no direct connection between the gasoline-burning engine and the Volt's planetary gear set. Rather, the engine delivers power to the vehicle's generator-motor, which relays it to the ring gear of the planetary gear set. The bottom line is it's not a direct mechanical connection in the manner of a conventional gas-burning car, but the generator-motor arrangement is similar to that of a Toyota Prius, which is a true hybrid.

Still, GM insists the Volt should still be considered an EV. "It's clearly an electric vehicle," says Pamela Fletcher, global chief engineer for the Volt and for GM's plug-in hybrid electric powertrains. "You can accelerate from a stop to 100 mph and have the engine never come on. You could take the internal combustion engine out of it, and it would drive just fine. But if you took the battery out, it wouldn't drive."

b) Another excellent article with pictures (thanks WOT and others):
Chevy Volt Delivers Novel Two-Motor, Four-Mode Extended Range Electric Drive System; Seamless Driver Experience Plus Efficiency
http://www.greencarcongress.com/201...-electric-drive-system-seamless-driver-e.html

c) Deep dive videos: http://www.youtube.com/results?search_query=Chevy+Volt+Powertrain+Deep+Dive
 
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#2 ·
I do not like this explanation at all. Misleading at best and wrong in at least one case. Examples follow (and it's not just semantics):

“At low speeds, the engine spins the generator-motor, which replenishes the battery.”
I think it is more correct to say: At low speeds, the engine spins the generator-motor. This provides electrical power directly to the traction motor. It also periodically charges the depleted battery just enough to maintain a small reserve for higher power needs, such as hard acceleration.

“Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set.”
Now this is just completely wrong. It should say (and herein lies the controversy they refer to): Unlike the other modes, however, this one calls for the internal combustion engine to transmit power directly into a ring gear in the vehicle's planetary gear set.
 
#3 ·
I do not like this explanation at all. Misleading at best and wrong in at least one case. Examples follow (and it's not just semantics):
Now this is just completely wrong. It should say (and herein lies the controversy they refer to): Unlike the other modes, however, this one calls for the internal combustion engine to transmit power directly into a ring gear in the vehicle's planetary gear set.
If you believe the diagrams posted earlier the ICE does not transmit power "directly" into the ring gear but is connected to the motor/generator which in turn is connected to the ring gear. So the ICE, motor/generator and ring gear are connected mechaically as a unit. Then Yes the ICE provides power mechanically to the planetary but thru the motor/generator route.. The question I have and have raised before: does the motor/generator also at this time generate electrical power(from ICE motive power) to drive the large motor? It could very well if the ICE had more power than was required to drive the ring gear at the requested RPM.
 
#6 ·
Appears to me that Pamela's discription is exactly what I stated. The last diagram she shows also shows a transfer of electric power from the generator/motor to the main motor and battery and since the arrows are double ended, back to the motor/generator from the battery. All bases are covered in this arrangement that has all sections of the drive participating at once. And the software is sophisticated enough to operated the crossovers seamlessly. A Marvel!!!
 
#7 · (Edited)
I liked their description...because it breaks it down fairly simply info *four* modes...I was not trying to raise the controversy again and bring out the haters/trolls.

http://www.designnews.com/article/511165-Electronics_Boost_Chevy_Volt_s_Efficiency.php

Electronics Boost Chevy Volt's Efficiency - The Chevy Volt is more than a green vehicle. It's a smart, seamless driving machine that in some cases exceeds the performance of gas-burning cars.
Charles J. Murray, Senior Technical Editor, Electronics -- Design News, November 16, 2010

<snip>
Voltec drive unit now has four basic modes of operation: electric driving (low- and high-speed); and extended range driving (low- and high-speed).

Here's a quick look at the four modes:

Electric Low-Speed [in Charge-Depleting (CD) mode]: The simplest and most well-known of the Volt's four modes, this calls for the vehicle to use the charge from its 435-lb lithium-ion battery pack to power a 111-kW ac traction motor. When the traction motor turns, it transmits power to a sun gear in a planetary gear set, which turns the drive axle. Volt owners are expected to make heavy use of this mode - many will drive the car to work and back, charge it at night, and never use a drop of gasoline in the process.

Electric High-Speed [in Charge-Depleting (CD) mode]: The Volt typically hits this mode at about 70 mph. Then, the supervisory controller splits the power between the large traction motor and a smaller 54-kW generator-motor (which is still operated by the battery). The planetary gear set blends the power from the two motors and sends it to the drive axle.Unlike the other mode, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency Even as it switches to this mode, however, the Volt still isn't employing its internal combustion engine - and therefore still isn't burning any gasoline.

Extended Range Low-Speed [in Charge-Sustaining (CS) mode]: When the battery's charge drops to an unacceptable level, the 1.4 liter I-4 engine (ICE) makes its debut. At normal speeds the engine spins the generator-motor, which provides power for the main drive motor and also replenishes the battery to an acceptable charge level.

Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split as in the above high speed (CD) mode, but goes one step further. It calls for the Internal Combustion Engine to be connected to the smaller motor-generator and mechanically provide further power directly to the ring gear in the vehicle's planetary gear set while at the same time generating electric power to drive the main electric motor.>
Sidebar:
Scott2000,
I suggest the drive mode descriptions be edited to something like the above editing I have made.
 
#8 ·
Scott2000,I suggest the drive mode descriptions be edited to something like the above editing I have made.
Can you put your edits in [] so I know what changed? It was a little hard to pick up at several glances. I also change the format in my original post to show it is a quote from the article and where I added []'d info.
 
#10 · (Edited)
Thread Title said:
Voltec drive unit now has four basic modes of operation ?
ALWAYS DID!
But the one caveat I is the controversial 2 motor combined mode where ICE is contributing torque to the ring gear (though C2 and C3) is only used when torque demand is relatively light at speeds above 36mph. Under high demand it switches to "pure" series 1-motor electric mode with the power demand handled by the 5 5kW generator and RESS "in tandem" and it operates in this fashion all the way up to maximum speed! ;)
WOT




 

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#11 · (Edited)
ALWAYS DID!
It's got at least 5 modes, not just the regular 4. It's got reduced power mode, which is a very different driving experience. Or is that just a sub-mode of the CD < 70 MPH mode? I'd say it's different, because of the ICE behavior (ramps in CD < 70 MPH, rails in reduced power).

Possibly 6 - reduced power mode due to engine malfunction (and OOG) is very different than reduced power mode due to depleted battery.
 
#13 ·
Per Andrew Farah: ... reporting that the magic cutoff speed of 70 mph is what the car uses to determine whether or not to make the engine to partially drive the wheels is incorrect. The engine is used to partially drive the wheels when the car calculates that it will be a more efficient use of the engine's power. There is no hard cutoff point.

http://www.plugincars.com/exclusive...rivetrain-says-volt-electric-vehicle-90758.ht
 
#14 ·
When the following drive mode begins, does the LCD screen in the VOLT change in any way so you know that it has begun?

Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split. It calls for power to be delivered through the big traction motor and through the smaller generator-motor. Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency."
 
#20 ·
If I understand your question correctly, going from CD to CS at high speed truly is almost imperceptible, mostly due to road noise hiding any ICE noise. I only notice the switch because of the display change: the battery cartoon fades away, and a gas-pump cartoon zooms into view.

At lower speeds the switch from CD to CS is more noticeable. You actually can hear the engine start, if you know to listen for it. Clearly a bunch of smart code was written to minimize engine noise and make it more-or-less responsive to speed and (in some cases) accelerator position. The ICE does get louder when you "hit the gas."

Chris
 
#21 ·
Sorry, I wasn't clear with my question. I'll try again.

When switching in and out of the fourth mode described below from/to the third mode (i.e. all in CS mode), can you feel anything? I can't imagine that it's completely imperceptible. There's a lot of clutch movement and devices that have to come together at different speeds. I'm wondering if that feels like some kind of transmission shift.
 
#22 ·
When switching in and out of the fourth mode described below from/to the third mode (i.e. all in CS mode), can you feel anything? I can't imagine that it's completely imperceptible.
I've got over 5000 miles on my Volt, mostly CS mode on the highways/freeways. So mostly around 70 MPH. Until yesterday I had *never* been able to tell when it clutched in or out between those modes.

Yesterday on my way home from the CAB-fest I happened upon a pathology that *was* noticeable. But it was almost contrived and not likely to show up often. It would likely also be difficult to reproduce (without practice). And a lot of people probably wouldn't have even noticed it (a couple quick hesitations, about a sixth of a second apart).
 
#23 · (Edited)
Thanks, Rusty. That is exactly the type of thing I'd expect, but it's interesting to actually hear about it for the very first time (as far as I know).

Have any other Volt owners noticed anything in this situation i.e. in CS mode, when the Volt transitions between exclusively traction motor propulsion to hybrid propulsion at higher speeds?
 
#24 ·
"Extended Range High-Speed [in Charge-Sustaining (CS) mode]: This is the most complicated and controversial (see sidebar) of the Volt's four modes. With the battery depleted at higher speeds (70+ mph), the controller opts for a power split. It calls for power to be delivered through the big traction motor and through the smaller generator-motor. Unlike the other modes, however, this one calls for the generator-motor to transmit power directly into a ring gear in the vehicle's planetary gear set. GM says it has a good reason for doing this - electric motor efficiency typically plummets at higher speeds. "You're bringing down the speed of the main traction motor and supplementing it with the generator-motor," a GM spokesman says. "As a result, you're improving the efficiency.""

My understanding is a motor/generator can operate as a motor, or a generator, but not both at the same time. If this correct, how does the motor/generator produce electricity for the traction motor and act as a motor to send power to the ring gear?
 
#25 ·
...My understanding is a motor/generator can operate as a motor, or a generator, but not both at the same time. If this correct, how does the motor/generator produce electricity for the traction motor and act as a motor to send power to the ring gear?
I believe in this mode the ICE is supplying the power, not the motor/generator (M/G). Some of the ICE output is used by the M/G to generate electricity for the battery and in-turn the traction motor. The rest of the power is transferred mechanically through the M/G shaft to the ring gear. So, in-fact the M/G is not operating as a motor in Extended Range High-Speed CS mode. However it's shaft is supplying mechanical energy to both the generator rotor, and through the through the ring gear, the drive wheels.
Of course this is only based on what I nave read, I am interpreting the same material as everyone else here.
 
#27 ·
Right scottf200,
That is the information I used. The key wording is "deliver torque via the gearset". In combined mode the torque has to come from the ICE. For the M/G to produce torque it would have to be consuming electric energy not generating it. Electric power can't flow both directions in a wire at the same instant in time, at least not by the physics I understand.
 
#28 · (Edited)
This is correct, due to the physical layout, MG1 techncially "delivers" ICE sourced torque to the planetary ring gear during high-speed extended range operation.(and MG2 absolutley MUST be simultaneously delivering power to the sun gear for there to be any output via the planetary carrier) However during that time it is operating as an ICE driven generator. It cannot provide motoring torque and generation simultaneously.
WOT
 
#29 ·
I am in no way an automotive engineer. However I am in the engineering field. And I do not understand why one would not use the low RPM power inherent in the electric motor to gear it so that it does not need to ever go out of its efficient RPM range. Hub center motor? Or similar configuration. Direct drive?

Electric car with an ICE generator on board. When I 1st read about the Volt a few years ago, I just figured that’s what GM would do. KISS it (keep it simple stupid). Now I am sure there are some great reasons for the configuration that the Volt is using. But it seems way more complex that it would have to be.

I have gone out to YouTube and watched the 3 part video on the power train. And it does of a good job of explaining how it works. But wow that is complex. And to me complex means costly repairs down the road.

Just saying.
But I still want one.
 
#31 · (Edited)
. But it seems way more complex that it would have to be.

I have gone out to YouTube and watched the 3 part video on the power train. And it does of a good job of explaining how it works. But wow that is complex. And to me complex means costly repairs down the road.

Just saying.
But I still want one.
"Complexity" is relative to your point of refererence.
Most of the people complaining that it is "too complex" are obviously not well aquainted with powertrain engineering principles.

The reality is this system is very simple and far less complex than even a basic automatic transmission as used in many other cars on the road.Even the most simple 4-speed typically has at least 3 inter-meshed planetary gearsets combined with 4-6 clutches and/or bands in order to generate the numerous paths of power at different ratios. A six speed is even more complex.

Below is the powerflow chart for a 4-speed Turbo Hydramatic 4T65E FWD transaxle for comparison.

The beauty of electrically variable ratio transmissions is delivered ratios can be infinately altered by creating relative speed differences through the use of the electric motors. It's like having a tranmission driven by 3 independant input shafts.

The Volt drive unit is amazingly simple and an elegant engineering solution for numerous "challenges" in creating an EREV powertrain.

WopOnTour

 

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#33 ·
WOT,

I think you've cleared things up: MG1 (the motor-generator) cannot suck (electrons) and blow (electrons) at the same time. It is the ICE that supplies torque to the ring gear in the fourth mode described earlier in this thread, not MG1.

I also agree with you that the whole setup is rather elegant and not too complex compared to traditional transmissions. I'll also add that I think GM made great decisions in figuring out how this should all work. Sacrificing significant efficiency to satisfy some preconceived notion would have certainly been stupid.

But you also said above: "due to the physical layout, MG1 technically "delivers" ICE sourced torque to the planetary ring gear during high-speed extended range operation." Frankly, to me, this obscures the truth and perpetuates a myth. Most people simply do not understand how this kind of transmission works and will quote this with complete misunderstanding of what is actually happening. We've already seen that happen in this thread and several others.

Here's how I view it conceptually (even if it is physically more compact than what I describe). There's a "shaft" that turns and ultimately drives the Volt wheels. There are 3 devices on that shaft: MG1, MG2 and the ICE. In the fourth mode described above (high speed CS operation):
-MG1 does not produce any motive power. It is acting completely as a generator, supplying electrical power directly to MG2 via wires, and maintaining the battery buffer if required.
-MG2 supplies torque to the wheels via its connection to the planetary gear set.
-The ICE supplies torque for MG1 via the shaft and also supplies torque to the wheels via the shaft which is connected to the planetary gear set.

The fact that MG1 happens to sit between the ICE and MG2 on a common shaft should not lead anyone to the conclusion that it powers the wheels, either directly or indirectly, in this mode.

Why the confusion to date? Simple Marketing 101 by GM: Product differentiation. They do not want the masses to view the Volt as a hybrid ... which is exactly what it is (by definition) in this mode. Well, more power to them if they can make it stick.
 
#34 · (Edited)
Actually you still appear to have it twisted up a bit and that IMO is what is exasperating your confusion.
I'll attempt to clarify but please refer to the basic schematic shown in the diagram above in Scott's post #26
Sticking with your "shaft" simplification (no pun intended) and terminology:

First of all ICE, MG1 and MG2 are NEVER on the same shaft

-MG2 will ALWAYS have it's own shaft (the unclutched sun gear connection) and will be a constant power provider in both EV and ER modes and is the SOLE provider during low speed EV mode.

-At higher speeds while in EV mode MG1 CAN be provided a shaft (via a "high speed" C2 clutch directly connecting it to the internal or ring gear) which in a way is "added" to the pre-existing MG2 shaft (although this results in MG2 reducing it's speed because of the MG1 "assistance") So MG1 and MG2 both in motoring mode and ultimately (through the gearsets) driving the wheels

-In Extended Range (ER) low speed mode MG2 is the sole driveshaft but a "series" C3 clutch permits ICE to drive MG1 as a generator to create the required electrical energy (i.e. series/serial hybrid mode)

- at higher speeds in ER the same "high speed" C2 clutch reconnects MG1 to the ring gear as it did before. But as it is still acting as a generator and being driven by ICE (via the "series" clutch) the actual torque being provided to that shaft is sourced from ICE (or more importantly the faster ICE turns the more more MG2 is permitted to slow down in order to maintain the same road speed)

The only element missing here is the C1 "brake" clutch which holds the ring gear solidly to the case when in low speed mode, and released to permit the MG1 shaft to drive it (assuming C2 is also applied) either electrically in EV mode or mechanically in ER.

Does that make any more sense to you?
Your "shaft" theory is a suitable analogy tool for most people however simply cannot explain what takes place with respect to the relative speeds and torques in a 3-member planetary arrangement such as this.

Trust me I'm not "propagating ANY myths" just attempting to explain how it works to those unfamiliar with the dynamics of this type of powerflow.
HTH
WopOnTour
 
#35 ·
WOT,

Thanks for the clarifications. Yes, I realize that my "shaft" analogy has limitations.

But I still do not see the justification for saying ""due to the physical layout, MG1 technically "delivers" ICE sourced torque to the planetary ring gear during high-speed extended range operation."
 
#36 · (Edited)
Well because, that's exactly what it does! (there's nothing incorrect about that statement)
At worst it's an over-simplfication of the drive unit's "on-axis" design. There might have been less elegant solutions to accomplish something similar, like a chain drive or another planetary with more clutches for instance.

So in terms of paths of power to the wheels:
(and attempting to stick to your "shaft" nomenclature)

Low speed operation (EV or ER) is:

MG2>SUN ::::::::::::::::::= CARRIER>FINAL DRIVE>WHEELS
*RING is HELD

High Speed EV is:

MG2>SUN
+ :::::::::::::::::::::::::::::= CARRIER>FINAL DRIVE>WHEELS
MG1>C2>RING

High Speed ER is:

MG2>SUN
+ ::::::::::::::::::::::::::::::= CARRIER>FINAL DRIVE>WHEELS
ICE>C3>MG1>C2>RING

So in this design, the only way for the ring gear to be driven is via MG1 and therefore in order for ICE to drive the sun it must be mechanically through MG1 (and via the clutches of course)
AND
During "high speed" operation since the speed of the carrier (output) will always be an average* of the speeds of the sun and ring gears, their ratios can be variable. Electrically variable in EV mode by controlling the RPM of MG1 vs MG2 and electro-mechanically variable via controlling the speeds of ICE and MG2. (MG1 speed will merely follow ICE since it's driven directly via the "serial" C3 clutch)

* a weighted average based on the actual tooth counts and associated ring and sun, to carrier ratios

HTH
WOT
 
#44 ·
I have some probably-not-important detailed questions, but since they popped into my head, I'll ask anyway:

When the car is shifted to 'N', does the C1 clutch disengage? Or is MG2 simply not powered and allowed to spin?

When transitioning from low-speed CD to high-speed CD, I assume C1 and C2 are both engaged briefly before C1 is released and power starts flowing into MG1. How long does this transition take?

How does it transition from high-speed CD to high-speed CS? Is C3 simply engaged while driving, allowing the planet-sun gear to start the ICE, or does it have to release C2 before engaging C3 to allow MG1 to start the ICE?
 
#48 · (Edited)
Volt Drive Unit from 0 - 100 mph - CS (Extended Range) 1 of 4

So this post is for George! :)
Been puttng this off for far too long
Finally got to creating some graphics of CS snapshots taken in GDS2 showing CS (extended range) behavior within the transaxle
There are 18 screenshots numbered in order (with a certain amount of time between them) showing the transaxle behavior from 0 to 100 mph.
(in approx 10 mph increments)
These are all parameters gathered "live" from the Hybrid Control Powertrain Module (HPCM) one of 33 modules on the car.
Since I can only add 5 attachments per post, I'll span them across 4 in total
I'll try to add more information to each as I can, or as questions arise
Enjoy
WOT

In Park 0 MPH

In Gear 0 Mph

10 mph Low speed EV in CS

20 mph Low Speed EV in CS

~30 mph Low Speed EV in CS
 

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#52 ·
There are 18 screenshots numbered in order showing the transaxle behavior from 0 to 100 mph.
Do I guess correctly that Transmission ISS and OSS are "Input Side Speed" and "Output Side Speed"? That would make some sense, except for the snap shots at TS=41.890 (59.62 MPH, OSS=1701 (Go Enterprise!)) and TS=42.190 (60.24 MPH, OSS=1699). The DashDAQ has an entry for Transmission Output Speed, so I guess I should go back and check the correlation between that and vehicle speed. But I recall seeing it do odd things some times.

The DashDAQ lacks Clutch <n> Status, but does have info on Clutch <n> Slip Speed (oddly, the DashDAQ has entries for clutches C1-C4!). What's indicated by the slip speed? Is it the speed of one side of the clutch relative to the other? And that would mean a high value would indicate a released clutch?

All fun stuff!
 
#49 · (Edited)
Volt Drive Unit from 0 - 100 mph - CS (Extended Range) 2 of 4

2 of 4
WOT

~30 mph ICE lights up (pure series CS mode commences)

40 mph pure series CS mode

50 mph pure series CS mode

57 mph transition to 2-motor combined mode begins

58 mph in transition to 2-motor combined mode
 

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#50 · (Edited)
Volt Drive Unit from 0 - 100 mph - CS (Extended Range) 3 of 4

3 of 4
Keep in mind I was pushing it prettry hard (note the ~35% throttle)
So the load variable (driver requested torque) was somewhat higher than what would be ideal for improved efficiency / economy
For this reason the transition to "2-motor combined" began a bit earlier than the 70mph speed usually associated with this shift
WOT

~58 mph in transition to 2-motor combined mode

~59 mph in transition to 2-motor combined mode

~59 mph transition to 2-motor combined mode near completion

~60 shift to 2-motor combined mode complete
 

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#58 · (Edited)
3 of 4
Keep in mind I was pushing it prettry hard (note the ~35% throttle)
So the load variable (driver requested torque) was somewhat higher than what would be ideal for improved efficiency / economy
For this reason the transition to "2-motor combined" began a bit earlier than the 70mph speed usually associated with this shift
WOT
WOT: thanks.. this is great stuff.

Is the 70mph really properly associated with mode 3 or did the GM engineers in the talks were I heard that just use 30 and 70 and example where mode 2 and mode 3 are happening and then leave unclear what is in the middle. I remember someone saying its a function of demand (as you show here) and other load on the car.

To me it was very interesting to note the engine RPM at 50MPH (before the transition to Mode 3 starts) was 3261 but after its done at 60rpm its down to 2718. Thus it is quite possible that the CS fuel efficiency is better at 60mph than 50mph. Even at 70mph it was 3200rpm (so lower than 50mph) and 80mph was 3259rpm or about the same as 50mph. Of course, these were not steady state and this is not RPM not actual fuel usage so harder to be sure, but it is suggestive and intriguing.
 
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