Ziv was mentioning that he read that GM wanted to originally achieve 50mpg out of the generator in CS mode but didn't to keep the Volt more quiet and to have a smoother ride. I'm a bit split on that decision, I enjoy how quiet the Volt is in CS mode for the most part but I'd also like to get better CS mileage. Coming from a cdi diesel car it urks me to see how fast the gas burned numbers go up when the generator is running. I'm used to getting 65mpg with the smart. I've been practicing all the discussed volt driving techniques to maximize my mileage but I'm still only getting in the mid 30's on the commute I have to do.

So I was wondering if anyone had any ideas of mods or maybe adjustments that could be made to the generator to improve it's CS mileage? I'd be willing to put up with some more noise to get another 10mpg. I do have the bose speakers after all, the extra bass will drowned out any extra noise the engine makes.;) I haven't heard of anyone plugging in and playing with the computer yet other than reading what is doing, but maybe I've just missed a topic on that.

Any thoughts, theories, out there?:confused:

Sadly I doubt the design engineers were responsible for this change.
Engineers are trained to make items as efficient as possible; only after the accounting and marketing are allowed inputs does the efficiency go down.

If Chevy had of sent a poll out to all prospective Volt buyers (ie. people who had pre-ordered) about the choice of a few decibels of sound or 60% better gas efficiency the choice would probably have been overwhelmingly in favor of the gas efficiency.
The people who never use gas really would not care and those of us who are forced to would care very much.

Sadly as in most cases the customer desire is never determined prior to them selling the product... :(

The member here with the world record EV range gets the CS numbers you want. I "think" he puts it into Mountain Mode on the flats and downhills and puts it into normal mode going up hill so as to use the battery rather than have the generator rev higher.... I haven't tried it myself yet.

MrEnergyCzar

I might have to try that. Though I get good EV since I drive mostly downhill to get to work, but sadly that means I have to drive up hill to come home.

If you had "pulse and glide" where the engine ran at max efficiency on the highway for say 10 minutes, then it slips back to CD-mode for 10-minutes and back and forth and it gave 45-47mpg, would you use it? I know it's not TDI efficient at 60mpg as some see in Europe with the Ford Blue's, but I think GM has admitted they wanted to down-rev the engine in CS-mode if the hp needed at the wheels is lower (ie. highway cruising) making it a more "pleasurable" ride. It may also give some life to the batteries by not having them go through charge/discharge cycles while on longer drives. And it's probably also a software change to make it happen.

By messing with Mountain Mode as stated above by Mr. Energy Czar, other drivers have gotten 45+ mpg on the highway using a "manually controlled pulse and glide".

Also, in winter months - check your tire pressure regularly. Most higher mpg guys are running 38+ psi.

Ziv was mentioning that he read that GM wanted to originally achieve 50mpg out of the generator in CS mode but didn't to keep the Volt more quiet and to have a smoother ride. I'm a bit split on that decision, I enjoy how quiet the Volt is in CS mode for the most part but I'd also like to get better CS mileage. Coming from a cdi diesel car it urks me to see how fast the gas burned numbers go up when the generator is running. I'm used to getting 65mpg with the smart. I've been practicing all the discussed volt driving techniques to maximize my mileage but I'm still only getting in the mid 30's on the commute I have to do.

So I was wondering if anyone had any ideas of mods or maybe adjustments that could be made to the generator to improve it's CS mileage? I'd be willing to put up with some more noise to get another 10mpg. I do have the bose speakers after all, the extra bass will drowned out any extra noise the engine makes.;) I haven't heard of anyone plugging in and playing with the computer yet other than reading what is doing, but maybe I've just missed a topic on that.

Any thoughts, theories, out there?:confused:

The number one thing you can do to improve mileage is to slow down! Of course, this probably falls in your "better driving" category. :)

I haven't tried it myself yet, but the MM pulse and glide should probably be your first thing. Basically, you driving in normal or sport until the generator kicks in. At that point, you switch the car into mountain mode. The car responds to this high demand by running the engine at higher RPMs for a while to rebuild the battery charge (the higher RPMs are substantially more efficient.) As soon as the engine slows back down to nearly inaudible levels, you switch back into normal or sport and drive electric for 10-15 miles, then repeat.

As I said, I haven't tried it, but people were reporting a 10-15% improvement with this technique. The car actually does something similar itself at lower speeds - at 55 in steady state it runs the engine (at low RPMs) for 6-8 miles, then runs electric for about 1.5 miles and repeats.

If you are going far enough to need to use the ICE, then playing some MM games may help.
Basically drive on EV until you have 3-4m EER range left, then enter MM mode. It will rev harder to provide both the power needed to drive, and to charge back up the battery. The trick here is that is the marginal energy needed to recharge the battery (even given its inefficiencies) and then use it for EV mode driving, is lower than the power needed to drive in CS mode.

I discuss my experience in a few threads, eg.
http://gm-volt.com/forum/showthread.php?10210-Holiday-100-Mile-Drive-Mountain-Mode


This week I had a medium trip (67 miles) and so needed some CS mode, but it was much colder (16 or so) and between the cold, the shorter run, the all up hill (1200 ft or so) and the morning's 5 "ICE running for temperature I only managed just over 35mpg.

Ice running for temperature is rough on milage if you are not going far. The engine only revs at 1800rpm, so i don't think its generating electricity then, but don't have the ability to measure the EV side of the volt yet, just the ICE). So for 5 "heat" runs it used .2 gallons and only covered about 2 miles. (Many of the temp runs were at stop signs, which was particularly frustrating). I eeked out 39 miles EV, and the whole 67 mile trip only used .73 gallons, so if I subtract out the "heating ICE runs and their miles (and I assume it did not generate electric miles), then my MPG would for the MM Game/CS section was in the range 44-49MPG (I'm using a range since I did not keep written logs for all of this, had to go back to voltstats.net to get numbers. I'll note computing milage when playing MM games is tricky. The data reported by the car is useless and even voltstats.net becomes hard to use meaningless unless you track some added data. I've tried various ways and setteled into us drive EV down to 2-3 miles, then reset a trip odometer so I can track miles/gas after that. I did not do that for this last 67mile trip so i could easily be off in my computation a bit. And the trip is too short for it to really be accurate. I like leaving it in CD/EV mode and playing MM as then I know when I've almost used up my buffer. If I let it go down to CS mode, its harder to known when the Bump up MM again.)

In the past I was not using MM when going very fast (75mph) or uphills thinking it was pushing the engine too hard (sounded bad). That made things more complex. But I'm not sure its correct.. I'll report when I know more. (Its going to be cold this week so even if I don't need CS mode, my Ice will run in which case I might do some RPM testing).

I don't have a Volt, and my present Buick Regal gives me about 20 MPG after a few engine fixes and improvements. But even with that "low" MPG, I still save money on gas every day compared with my travels thirty years before.

The best solution? Move closer to your daily destinations!

I lived seventeen miles from my job, and bought a full tank every week. Now I live only six miles from my job and fill up only once every two weeks.

So if you cannot buy an EV, and gas prices are hurting you, move closer and travel less.

Wainair, our drive is fairly similar, but you probably have the edge for mileage as most of my trip is the 100 Km/hr highway speed, and I think a lot of yours is 80 Km/hr. All cars are much more efficient at the 80km speed. If you check my stats on voltstats.net you will see that I am flirting with 40 mpg. I really think all you have to do is slow down when in CS mode. I commute so much (23 years @ 45,000 Km per year), that the only way I can relieve the boredom is to make up little games. Can I beat the mileage I got yesterday, can I acheive a personal best, etc. I have done this for years even in "normal" cars. It was funny, I didn't have to change my driving habits much for the Volt. I already anticipated slowing and coasted, the only thing I do differently now is L for regen sometimes.

A few thing I noticed years ago when I slowed down. 1) I saved a ton of gas (expected). 2) The ride was quieter, and much less stressful as I wasn't always on the lookout for cops, and 3) I didn't get pissed of at the other drivers who were going slower than me in the fast lane. I drive in the slow lane (at the speed limit!), slow when necessary to allow merging traffic and enjoy the ride. 4) My brakes and tires lasted for ever. I usually get 160,000 km out of a set of brakes, it is going to be interesting to see if I ever have to replace them on my Volt.

Considering I have a job that is listed as one of the most stressful, my ride being actually de-stressing helps. The Volt even more so since it is so quiet.

One of the things I used to think about after I slowed down was the silliness of the go fast mind set we as a society have fallen in to. Because I had lots of time to think (50 min each way commute). Here is what I came up with. If I increased my speed from 100 km to 120, the most time I would save would be 7 min (68 km/ 1.6 km per min against 68 km/ 2 km per min). In reality not all of the trip is at highway speed, and traffic lights amount to the same speed, zero. So I estimated 5 min saved per trip max, but I had to stop for gas every 4th day instead of every 5th if I slowed down. So how much time was I really saving. What really amazed me was if some gas station dropped the price of gas by 5-10%, people would line up for 20min or more to save the money, when if they slowed down they would have saved the same amount!

So leave 5 min earlier, slow down and enjoy the Volt.

Sorry for the rant, but if we really want to stick it to OPEC, slow down!

Ziv may have been referring to what Jon Bereisa said about the Volt development: "When we modeled the Volt's engine, theoretically we could have gotten to high 40s or low 50s mpg in gasoline mode. But we would have had to run it continuously at 3500-3800 rpm and just switch it on and off, and the noise and pleasability wouldn't work. We had to drop it down, which got us to 37-38 mpg. But I think a lot of fuel economy still can be gained without major expenditures in tooling or engineering."

I doubt there is any magical way of increasing your MPG. The Volt drive train is what it is. However, one thing that puzzles me is your experience with your diesel. The Volt is rated 40 MPG Highway and all the diesel sedans are rated 42 MPG. Factor in that the fact that diesel fuel has a much higher energy density, and that the Volt will have a much lower CdA than the diesel's, and it seems strange that you're get so much better MPG from your diesel. In traffic it won't be close because the Volt uses the battery and has regen (35 MPG vs. 30 MPG).

One other thing I do, though I don't have any data to support the position, is I drive in Cruise-control almost all the time, even on surface streets. And on the HW it lets me set the limit and no more (which means right lane most of the time, not left as I'm used to).

My hypothesis is that CC lets the car be more more efficient even at 45mph. The 2-motor design, or in CS thee 2EV+ICE mode, is more efficient (10-15% by GM statements) but reduces power and acceleration, so if you are driving by foot, and hit the gas just a bit it may drop back to just traction motor (or Serial mode if in CS), to prepare for acceleration.

When we first drove the volt home from TX, my wife and I traded off. On the first day, I drove in CC, and she never does. I averaged 41MPG, she did 38MPG. Of course there were other differences but to me that was telling. She kept complaining that I must have been driving slower or she had more uphill..

And I have inflated to 40psi.. (even in winter I keep them there). No hard evidence on its difference but the logic of reduced rolling resistance makes it seem like an obvious step.

to what Jon Bereisa said about the Volt development: "When we modeled the Volt's engine, theoretically we could have gotten to high 40s or low 50s mpg in gasoline mode. But we would have had to run it continuously at 3500-3800 rpm and just switch it on and off, and the noise and pleasability wouldn't work. We had to drop it down, which got us to 37-38 mpg. But I think a lot of fuel economy still can be gained without major expenditures in tooling or engineering."
Article on this and other interesting tidbits:
http://www.green.autoblog.com/2011/11/03/where-does-erev-technology-go-from-here/

They left some MPG on the table for the sake of NVH and emissions but certainly not 10 or more. Referring back to the quote, they were modeling behavior, presumably based on the 3 cylinder turbo engine that never appeared.

My (somewhat educated) guess is that gaming MM gets back a fair percentage of what was left on the table. The RPM you see when the car is charging in MM, ~2800, is apparently the sweet spot for converting gasoline to electricity with the current powertrain.

It's a shame they didn't provide an ECO mode that would let the system eek out maximum efficiency, NVH be damned, but I don't know what ramifications that would have with EPA certification, etc. And don't forget the reviewer issue - if it were particularly awful, that's all we would hear about in test reports, rather than "I couldn't even feel the transition to ICE power!"

Good suggestions all around but I was thinking more along the lines of fuel mapping / modding to create your own pulse and glide mode... though I suspect that is sort of what you are achieving tboult with how you are using MM....I live on cruise control too. The car is much more gentle with the gas pedal than I am.

Minfuel, I agree slowing down is the best thing anyone can do, but HONEST, since I've bought the Volt I've become a speed limit follower. Even in those ridiculous 60km/h zones that have popped up everywhere in the last 10 years. I live in the right lane, I don't do jackrabbit starts anymore, I don't have to be there first! I get it, but I'm still only averaging 34.71mpg according to voltstats. I really do think it is the geography of my commute. I'm up and down a lot of steep rolling hills, a much steeper grade than what you see on the 401 and I really think that chews up the electricity more than driving at 100km/h. Oh and there is no way I could do your job. I'd be babbling in the corner under a desk after one week! :) LOL

Yes DonC the cdi smart was amazing in what you could get for mileage but it was pushing around a lot smaller car and it was a 800cc three cylinder turbocharged engine. I could get to work on less than 2 litres of diesel. The Volt nearly doubles that in the same area. Now I don't expect you could ever get the same kind of mileage in the Volt on CS as you could with the smart, but I think with some changes/mods CS numbers could be improved.

But my driving technique aside I'm thinking there are probably modifications that can be made to the generator so it uses less fuel but still provides the same amount of energy for the drive system.

I'll have to read that article. I haven't had a chance yet.

Wainair,
That is an odd phenomenon, but I've become a speed-limit follower (pretty close at least) as well since getting the Volt. In my previous hundreds of thousands of miles driving experience, I wouldn't have considered staying within 5 mph of the speed limit. But now I'm in the right lane quite a bit.
There are a lot of features in the design of this car that impress me, but one of the best is still the green ball. Imagine what would happen if every car manufactured in the U.S. was required to have one of these on the dash (that you couldn't turn off). Sure, some folks would completely ignore it. But a significant number would play the same games that nearly all of us do, especially when gas prices start heading back up. Imagine the impact of U.S. transportation fuel consumption. The green ball is a great performance/insurance tool for GM to have included in the Volt. They've been able to improve real-world performance and owner results not only through design mechanics of the car, but by modifying our driving habits as well in a way that does not feel intrusive.
P.S. - I noticed in our drive back to the house this afternoon that my wife is one of the ones who completely ignores the ball. Have to work on that one!

I get it, but I'm still only averaging 34.71mpg according to voltstats.


Ah.. that might be a bit of the issue. My Voltstats are only 37MPGcs (Closer to 44 but MMgames break that). More significantly Nov they reported 455MPG overall, but in Nov I drove 620 miles and only used .979 gallons.


You might want to do your own computation for a while. If you are on voltstats download your personal CSV and do your own math.

Trying to figure out my MPG using voltstat's MPGcs was driving me nuts when I started.
Mike has done a great job on Voltstats, but the Car does not really report gallons used or CS milage. The car is doing its math almost exclusively in fixed point (mostly 16bit) which can lead to lots of small/accumulated errors. Mike has to estimate gallons uses and MPGcs from the actual variables reported (Total EV miles, Total Miles, Trip EV Miles, Trip Total Miles, Lifetime MPG, etc). There are weird reporting and accumulated errors, e.g. where the EV miles for a trip are != Total miles for the trip even though the ICE never comes on. The reported lifetime MPG has its own errors with some weird biases (maybe factory or pre-owner pickup) that make the math incorrect, for some cars, when you convert the MPGcs using it.
I presume mike is computing CS Miles = (Total Miles-TotalEV), and
GallonsBurned = Totalmiles/LifetimeMPG
But gallons burned > total gas my car has used (presuming the GallonsofGas (in tank) is correct, its over my more than a gallon for my car.) And then estimates MPGCs = CSMiles/GallonsBurned, but if GallonsBurned is too large, the computation underestimates your MPGcs. This seems to be more of an issue for people that don't drive a lot of CS miles.


I tried to model the errors reported at Voltstats for my car, buts its non-linear and after a few tries I just gave up. I also learned quickly that the MM games totally hose that computation as does "regen CS" + a stop (which converts some CS into EV). So that is why I use the trip meter + the log (- EV miles used before playing MM).

The Voltstat csv will allow you to track actual gas in the tank, which does vary with temp a bit.
But with that, and some personal logging, you can do your own milage math. Might want to try that for a trip or two. You might even just pull the existing logs and if you have not put in gas recently you might do your own computation (using delta gas in the tank vs a local trip CS miles (which are more accurate as there is no accumulated error).

Ah, that's interesting. I didn't realize that there was/could be an error in the way voltstats reports CS mileage. I've always thought my numbers were a bit low. I'll have to figure some numbers myself. Though I bet it will only be a small % error.

I read that article and the one line that jumped out at me was from that paragraph that mentioned they thought they could get high 40's low 50's mpg. The closing sentence was the most important in my opinion. "...But I think a lot of fuel economy still can be gained without major expenditures in tooling or engineering." That's the thing I'm thinking, that there is a lot more potential in that motor to run on less fuel than what it's doing right now.

Maybe I have to get a plug for my laptop too!

..... one of the best is still the green ball. Imagine what would happen if every car manufactured in the U.S. was required to have one of these on the dash (that you couldn't turn off). Sure, some folks would completely ignore it. But a significant number would play the same games that nearly all of us do, especially when gas prices start heading back up. Imagine the impact of U.S. transportation fuel consumption. The green ball is a great performance/insurance tool for GM to have included in the Volt. They've been able to improve real-world performance and owner results not only through design mechanics of the car, but by modifying our driving habits as well in a way that does not feel intrusive........

Excellent point!!! I'd be willing to bet we, as a nation, would save huge amounts of fuel... just with a green ball in every car :-)

Dunno about this case, but I've not yet owned a car where tuned exhaust headers and a slight remap of the other stuff didn't get me 10% or so. Noisier. Manuf's don't do headers as such (but at least they're getting better than the old log manifolds) for noise, and longevity - thin light tubing doesn't last that long...more underhood heat unless you do things to manage that...did I say noise?

This engine seems pretty darn good. I also own a 2012 Cruze turbo, and more or less struggle to get about the same mileage with that, usually it's slightly less, and that's a lighter car (though it has this evil lag in the throttle response by comparison). I haven't determined which is quicker yet. The Volt's definitely faster off the line, no excruciating "am I gonna get broadsided" when making left turns from a stop. The Cruze makes a lot more noise when it's working hard so it *seems* fast, but looking at the speedo update, I'm not so sure there either. Distance to speed is definitely less with the Volt due to that much better first coupla car lengths.

Could be that by eschewing the extra go you do better in the Volt, and that's the way I like it - up to the driver on the spur of the moment, not forced on you.

Ars Technica did an article on the green ball, titled something like the gamification of driving. It got a lot of comments, mostly by non owners. I chimed in and mentioned that if you find it obnoxious, you can just turn it off. I leave mine on, but don't watch it much any more. No need if you really already knew how to drive for mileage already, the same principles seem to apply here. Don't toe-tap, and remember if you need to use the brakes, that means you used too much accelerator sometime just before that.
So, go for maximum brake life and mileage tends to follow.

Dunno about this case, but I've not yet owned a car where tuned exhaust headers and a slight remap of the other stuff didn't get me 10% or so. Noisier. Manuf's don't do headers as such (but at least they're getting better than the old log manifolds) for noise, and longevity - thin light tubing doesn't last that long...more underhood heat unless you do things to manage that...did I say noise?

This engine seems pretty darn good. I also own a 2012 Cruze turbo, and more or less struggle to get about the same mileage with that, usually it's slightly less, and that's a lighter car (though it has this evil lag in the throttle response by comparison). I haven't determined which is quicker yet. The Volt's definitely faster off the line, no excruciating "am I gonna get broadsided" when making left turns from a stop. The Cruze makes a lot more noise when it's working hard so it *seems* fast, but looking at the speedo update, I'm not so sure there either. Distance to speed is definitely less with the Volt due to that much better first coupla car lengths.

Could be that by eschewing the extra go you do better in the Volt, and that's the way I like it - up to the driver on the spur of the moment, not forced on you.

Ars Technica did an article on the green ball, titled something like the gamification of driving. It got a lot of comments, mostly by non owners. I chimed in and mentioned that if you find it obnoxious, you can just turn it off. I leave mine on, but don't watch it much any more. No need if you really already knew how to drive for mileage already, the same principles seem to apply here. Don't toe-tap, and remember if you need to use the brakes, that means you used too much accelerator sometime just before that.
So, go for maximum brake life and mileage tends to follow.

I read that article too. I remember not a single person liked the idea - either people would be crashing from distraction, or "big deal" it's been done before, etc.

Dunno about this case, but I've not yet owned a car where tuned exhaust headers and a slight remap of the other stuff didn't get me 10% or so. Noisier. Manuf's don't do headers as such (but at least they're getting better than the old log manifolds) for noise, and longevity - thin light tubing doesn't last that long...more underhood heat unless you do things to manage that...did I say noise?


Have you looked underneath a Volt? The cat is where you'd normally have a downpipe, maybe 6 inches from the cylinders (which I'm sure is part of GM's strategy for rapid lightoff and dealing with engine cycling.) I tend to think there isn't much room for a header. I could be confused, but I thought tuned headers were mostly effective at a specific RPM? I'm not sure where you'd tune the header - probably pretty low unless you're gaming mountain mode.

Don't let the car run down to zero miles of electric range.

The first thing the Volt does when it runs out of EV range is turn on the engine and provide MORE power than it takes to drive. It does this to add charge back to the battery. The net effect is artificially horrible gas mileage. On longer trips it averages out, as the engine will ultimately drop to a point where the battery net-discharges for a bit, then back to net-charging. The problem is if you run out of battery 4 miles from home you end up adding charge to the battery with gasoline, when you'd be charging the car at home in a minute anyway. I see about 25 mpg during the first 5 miles of ICE running.

Although my gas MPG looks bad, here's how I game the system to get the best overall "gas" mileage:

When I get to about 6 miles of battery range left, I change to mountain mode. This instantly starts the ICE and not only runs the car, but adds charge. After a couple miles of driving I go back to standard mode. Generally it then has about 8 miles of charge. I run it down to 6 miles of electric range and repeat.

My portable charger broke last week, forcing me to drive 28 miles home on 12 miles of range. So I went the last 16 miles burning .4 gallons of gas, for exactly 40 mpg. But the car reported only 9 miles on gas, and 19 miles of electric. So my .4 gallons of gas to go 9 gas miles looks like only 22.5 mpg because it doesn't account for the fact that the ICE also gave me 7 miles of extra battery range.

Don't let the car run down to zero miles of electric range.

The first thing the Volt does when it runs out of EV range is turn on the engine and provide MORE power than it takes to drive. It does this to add charge back to the battery. The net effect is artificially horrible gas mileage. On longer trips it averages out, as the engine will ultimately drop to a point where the battery net-discharges for a bit, then back to net-charging. The problem is if you run out of battery 4 miles from home you end up adding charge to the battery with gasoline, when you'd be charging the car at home in a minute anyway. I see about 25 mpg during the first 5 miles of ICE running.

Although my gas MPG looks bad, here's how I game the system to get the best overall "gas" mileage:

When I get to about 6 miles of battery range left, I change to mountain mode. This instantly starts the ICE and not only runs the car, but adds charge. After a couple miles of driving I go back to standard mode. Generally it then has about 8 miles of charge. I run it down to 6 miles of electric range and repeat.

My portable charger broke last week, forcing me to drive 28 miles home on 12 miles of range. So I went the last 16 miles burning .4 gallons of gas, for exactly 40 mpg. But the car reported only 9 miles on gas, and 19 miles of electric. So my .4 gallons of gas to go 9 gas miles looks like only 22.5 mpg because it doesn't account for the fact that the ICE also gave me 7 miles of extra battery range.

I'm not clear what you are gaining by switching 'with 6 miles left.' Aside from that, this sound like the MM PnG described several places on the forum - AFAICT all switching at 6 miles does is make you switch modes twice as often?

By messing with Mountain Mode as stated above by Mr. Energy Czar, other drivers have gotten 45+ mpg on the highway using a "manually controlled pulse and glide".

Also, in winter months - check your tire pressure regularly. Most higher mpg guys are running 38+ psi.

I think it was Chris who showed pretty conclusively that "pulse and glide" is not more efficient with the Volt, but rather a low steady state driving achieves greater range. The most efficient speed being in the 30-35 mph range. I think pulse and glide was more efficient with older EVs because they use lead acid batteries. Those batteries can regenerate some charge if you let off of them for a moment. Li batteries do not do the same.

There is no magic to achieving higher range other than, slower speeds, easy accelerations, maintaining distance between you and the car in front so that you try to maintain momentum. If your daily commute includes driving at speeds north of 55 mph your range will be diminshed. And tire pressure. The tires are rate a max of 51psi so many are pushing 45 psi or higher.

but I'm still only averaging 34.71mpg according to voltstats

Not sure what to make of voltstats gas average. Whenver I have done any extended driving on gas I have never seen lower than low 40s, and often around the mid 40s mpg, according to the screen that pops up when you power down. Yet voltstats has my gas mileage pegged at 39.xx. The only time I see a number that low from the Volt screen is if I have driven a couple of miles or less.

Not sure which to believe. The Volt screen or voltstats.

Wainair,
That is an odd phenomenon, but I've become a speed-limit follower (pretty close at least) as well since getting the Volt. In my previous hundreds of thousands of miles driving experience, I wouldn't have considered staying within 5 mph of the speed limit. But now I'm in the right lane quite a bit.
There are a lot of features in the design of this car that impress me, but one of the best is still the green ball. Imagine what would happen if every car manufactured in the U.S. was required to have one of these on the dash (that you couldn't turn off). Sure, some folks would completely ignore it. But a significant number would play the same games that nearly all of us do, especially when gas prices start heading back up. Imagine the impact of U.S. transportation fuel consumption. The green ball is a great performance/insurance tool for GM to have included in the Volt. They've been able to improve real-world performance and owner results not only through design mechanics of the car, but by modifying our driving habits as well in a way that does not feel intrusive.
P.S. - I noticed in our drive back to the house this afternoon that my wife is one of the ones who completely ignores the ball. Have to work on that one!

I don't think the more efficient/safer driving is a green ball phenomenon. EV enthusiasts have noted for decades that when you get behind the wheel of an EV you drive the speed limit and no more. It is a preserve the range phenomenon. People do that in an EV even with no green ball, but no doubt the green ball helps people to learn to be more efficient more quickly.

It is the same reason that many people actually have lower electricity bills after buying a Volt. Driving electric causes them to think about how to conserve energy and you start looking at all the little ways you can do that, and it adds up.

Point of clarification: The PnG discussed here is quite different from the classic Prius PnG, and is generally executed at a fixed speed on cruise control. By cycling the Mountain Mode, you can cause the Volt to run the engine hard for a brief period and then run on electricity for a while, just like the Prius PnG, but at a constant speed. There's a fair amount of anecdotal data suggesting this is effective, though I haven't seen an instrumented test.

I wouldn't expect a traditional PnG while under electricity would help.

Point of clarification: The PnG discussed here is quite different from the classic Prius PnG, and is generally executed at a fixed speed on cruise control. By cycling the Mountain Mode, you can cause the Volt to run the engine hard for a brief period and then run on electricity for a while, just like the Prius PnG, but at a constant speed. There's a fair amount of anecdotal data suggesting this is effective, though I haven't seen an instrumented test.

I wouldn't expect a traditional PnG while under electricity would help.

ah...thanks for that Walter.

Not sure what to make of voltstats gas average. Whenver I have done any extended driving on gas I have never seen lower than low 40s, and often around the mid 40s mpg, according to the screen that pops up when you power down. Yet voltstats has my gas mileage pegged at 39.xx. The only time I see a number that low from the Volt screen is if I have driven a couple of miles or less.

Not sure which to believe. The Volt screen or voltstats.

When you're looking at the energy usage screen (which you can reach at any time by way of the leaf button BTW,) are you talking about the MPG it shows in the lower right, or are you taking the blue CS miles and dividing by the number of gallons used.

For the former, keep in mind that the car is literal about it and disregards electricity - it is the total miles driven (under electricity or gas) divided by gallons of gas. The second method above should give you an accurate number for MPG once the battery is dead, and is similar to what voltstats is supposed to be doing (I understand there have been some issues with the numbers however.)

I'm not clear what you are gaining by switching 'with 6 miles left.' Aside from that, this sound like the MM PnG described several places on the forum - AFAICT all switching at 6 miles does is make you switch modes twice as often?

See SAGHOST's post #27. Mountain mode forces the engine on in higher rpm/load configuration, which you can then turn off. Once you've dropped to zero battery range you cannot control the on/off cycling of the ICE and it often runs in lower, quieter - but less efficient - mode.

See SAGHOST's post #27. Mountain mode forces the engine on in higher rpm/load configuration, which you can then turn off. Once you've dropped to zero battery range you cannot control the on/off cycling of the ICE and it often runs in lower, quieter - but less efficient - mode.

Umm... You're quoting me back to me? I like it. :) But the question I was attempting to ask is why you switch with 6 miles left, instead of waiting until the EV miles run out and switching then instead. I haven't tried doing that, but off the top of my head I'm not seeing any benefit to switching early - the only differences I can see are that you'd switch more often in shorter cycles, and that the car might account it differently on the energy usage screen.

See SAGHOST's post #27. Mountain mode forces the engine on in higher rpm/load configuration, which you can then turn off. Once you've dropped to zero battery range you cannot control the on/off cycling of the ICE and it often runs in lower, quieter - but less efficient - mode.

We should have an FAQ entry for the 2 ways Mountain Mode (MM) affects the ICEs RPM and battery buffer.

From another thread (click on http://gm-volt.com/forum/images/buttons/viewpost-right.png for source) to help explain the 2nd one (diff than above).

It only "recharges" (charges up) if you forget to set Mountain Mode (MM) at or above the ~14. Otherwise it appears to be just a higher low water mark for the CS mode to start. ie. if I switch to MM at 20 miles away from my mountain and I have 30 miles shown on my battery it will immediate drop my battery miles to 16 (30-14). When I run down the 16 miles it will run like normal CS mode.


It definitely recharges the battery in mountain mode, to build a bigger buffer for hill climbing, up to ~14 miles of electric range if you switch it back to normal.

In normal CS mode though, it's only attempting to keep the battery at an approximately steady state of 20-something percent full, but constantly fluctuating up & down around that as power needs go up & down. The traction motor is running primarily off the generator's electricity, supplemented by the battery for extra power when needed. It'll recharge the battery only to restore that extra power buffer after use, but no more, as the idea is to not burn extra gas to charge up the battery since grid power is more efficient. If excess charge is built up, the engine may slow/shut down and let it drain off a bit.

Look at the middle portion of the following graph to get an idea what's going on.
http://www.gm-volt.com/i/voltchart.jpg

Aside: From a past thread:

http://gm-volt.com/2009/10/26/chevy-volt-engine-generator-operates-between-1200-and-4000-rpm/


The Chevy Volt’s 1.4 L 4 cylinder flex fuel generator garners a lot of attention and discussion online.

It is this range-extender that make the car so unique. Although the Volt always operates as an EV, once the battery’s state of charge reaches roughly 30% this generator powers on, providing electricity to the motor. Energy is also obtained from regeneration and the battery buffer when power demands are high.

GM has yet to publicly demonstrate the car operating in this charge-sustaining mode, but most accounts indicate it is unnoticeable.
In spite of many months of rampant speculation here, GM’s lead Volt engineer Andrew Farah has finally disclosed some details about the engine’s operation. He said the generator would “operate from 1200 to 4000 RPMs and from a 30% to 100% load.”
Further explanation comes from Volt Powertrain Engineer Alex Cattelan:

“We don’t keep it at a fixed RPM, we have a window of operation that is optimized. We have been able to optimize the engine for a window of efficiency but it is still best to change your power and torque levels within that window as the customer torque request varies.”

“We don’t want to always be operating at one state because really you may be putting too much energy into the battery or drawing too much energy out of the battery. It is still good to vary that engine power and torque. Not to follow exactly what the accelerator pedal does, but to optimize efficiency.”

Finally Volt vehicle line director Tony Posawatz explains it this way:
“In charge sustaining or range extender mode, the Volt will not follow the throttle position. The challenge is to select the right operating points (RPMs) that are 1.) efficient, 2.) pleasing to the driver, and 3.) meet regulatory requirements.”
And he teases us, “we are about ready to expose people to this experience.”

Umm... You're quoting me back to me? I like it. :) But the question I was attempting to ask is why you switch with 6 miles left, instead of waiting until the EV miles run out and switching then instead. I haven't tried doing that, but off the top of my head I'm not seeing any benefit to switching early - the only differences I can see are that you'd switch more often in shorter cycles, and that the car might account it differently on the energy usage screen.

We'll it was not my post but I think I posted before that witch with 6-1mile EER showing. 6 is not a magic number but its an okay place if you are in the right terrain conditions. I will sometimes switch at 6 because of the timing/terrain. I want to switch will still in CD (so i can better see what rang eI have left before next bump) and because I don't like to MM when I'm going gup a large hill. If I'm coming back from the airport and am about 24miles from home, I'm in a nice flat section, and as long as Iam at or below 6EER, then I'll pop into MM for about 8-9 miles, so so I can drop back to CD after Castle Rock when the speeds returns to 75mp up 10-12 miles of hills in EV (After the hill the last 4miles downhill so I don't need much at all).

I'm not clear what you are gaining by switching 'with 6 miles left.' Aside from that, this sound like the MM PnG described several places on the forum - AFAICT all switching at 6 miles does is make you switch modes twice as often?

The main reason for switching before it gets to zero is if you switch to close to zero ev range the car won't let you switch back out of MM without cycling the main power on the car(which involves putting it in park). So by doing it at 6miles range left you can go back into CD mode on the fly.

Umm... You're quoting me back to me? I like it. :) But the question I was attempting to ask is why you switch with 6 miles left, instead of waiting until the EV miles run out and switching then instead. I haven't tried doing that, but off the top of my head I'm not seeing any benefit to switching early - the only differences I can see are that you'd switch more often in shorter cycles, and that the car might account it differently on the energy usage screen.
LOL. Didn't pay enough attention I guess. By turning mountain mode on before I hit zero miles of electric range, I can always control when the engine runs and when it doesn't. Once it hits zero miles of range I lose that control. So for example, on a drive home I'll make sure the engine runs - and runs hard - while driving 75 mph on the highway anyway. Then when I'm going 40-50 on non-interstate I can run more miles on battery. I guess the only difference is more control. Not like I've had to do this much. Only have 100 gasoline miles total out of 3000+ miles so far. :)

The main reason for switching before it gets to zero is if you switch to close to zero ev range the car won't let you switch back out of MM without cycling the main power on the car(which involves putting it in park). So by doing it at 6miles range left you can go back into CD mode on the fly.
Gee - that's what I was trying to say. You said it better. Thanks!

I would add that avoiding the expressway and taking the city streets is far more efficient, though it takes longer. I have a location I travel to every so often. Taking the expressway there and back, with speeds of to 55-65, burn through the battery and requires gas on the return leg. Taking the stop and go side streets, where speeds are 35-45 results in left over battery range. As the saying goes, speed kills (battery range).

I just noticed this effect in Minnesota with the recent drop in temperature. I work about 2.5 miles from work and the ICE runs for a couple minutes twice on the way while my battery charge stays put full up. Any tips you can offer to max out a short commute like mine. I'm becoming an mpg junkie and I hate to watch it drop. :)