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Nice article, thanks for sharing.

As one of those that has been promoting MM for efficiency gains having it add to my buffer, I'm beging to reconsider just how much those gains really are inherent MM and how much was my timing. The results for others have been mixed and I wanted to understand why. (And build an app to help people with it).

As I said in previous posts I only used MM Recharge in flat/low speed and in downhill sections. While not a definitive test on a recent trip to Denver, with my wife driving, I was doing some logging of RPMs and such. (No MM games as she gets annoyed if I tough any button while she is driving and she does not like the increase RPM noise) and then on my commute to work (which does not usually use gas) I played a few MM games with logging. MM did push up the RPMs. (Too bad I cannot yet measure torque). But looking at the BSFC curves I posted here
http://gm-volt.com/forum/showthread.php?3739-VOLT-MPG-estimate-using-BSFC-maps

I can see maybe a only small gain in BSFC at rpms > 1600 (combining generator efficiency gains and engine BSFC gains) To get larger gains at those RPM gains depend on the toeque (which my current setup does not measure). But if demanded torque is low the car could reduce the RPM which I presume it does, trying to stick to the golden curve. Given the inefficiencies of battery charge/use, I cannot imagine that yielding an increase in overall efficiency. So if MM games really work it will only be in regions where the torque demand is very low <70nm if the BFSC is correct) and hence RPMs are < 1500. On the trip however, I definitely measured extended segments with RPM around 1400 and sections in 1300s, which could be much greater gains and hence justify MM. In those sections, entering MM to charge the battery took it to about 3000rpm which is a sweet spot. When RPMs were naturally higher, say 1900, because of the road load, the MM recharge push it to 3400RPMs which has a slightly worse BSFC (and given losses would be bad for efficiency).

So now I have a functioning hypothesis in when it can gain, and how to measure when to engage. I'd prefer a torque measurement but RPM is an okay standin for now. If rpm < 1500, use MM recharge, RPM > 3200, disengage MM recharge. I'll be testing that theory on my next airport run.

All of this is presuming the BSFC I found is correct which I've not been able to verify.. no reply from the original source and no external source yet. If someone inside knows and can tell me I'm barking up the wrong tree please save me some time.
 

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Guy is jerk.. How many small cars get 40mpg on gas?? This is was to bring out more bad than good.
 

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Another way to use MM is to use it to help warm up the cabin, after it has been parked without being able to plug in.

Why use battery powe for heat when you allready are at a low state of charge?

I would rather have the ICE running at the start of a trip if I know it will have to be running at the end if I dont.
 

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Guy is jerk.. How many small cars get 40mpg on gas?? This is was to bring out more bad than good.
Pretty agressive response.? I don't think he was bashing in any way or trying to bring out any negatives. (Well maybe implicit negatives about the EPA).

The only 40 in the article is him mentioning that his trip to see family was beyond his 40mils of EV range, and he used MM to allow him to show up at his family and instantly be able to demo EV/CD mode.

What did you see as negative?
 

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Pretty agressive response.? I don't think he was bashing in any way or trying to bring out any negatives. (Well maybe implicit negatives about the EPA).

The only 40 in the article is him mentioning that his trip to see family was beyond his 40mils of EV range, and he used MM to allow him to show up at his family and instantly be able to demo EV/CD mode.

What did you see as negative?

That is exactly the situation I was faced with today when I was going to visit a friend that has not seen my Volt yet and I was going to take him for a ride. I was 3/4 way there with 12miles of EV range left and it appeared that I was going to use EV range completely by the time I got to his house........so, I used MM for the first time ever (sorry 2nd time was going up a mountain); anyways, it took about 3miles more of EV range for the MM to come on and then it was gas from there to his house when I then switched off the MM. I was able to drive him around on complete EV range and was able to show him the amount of battery energy remaining on the centre stack. I was happy with the results.

I also like the idea of using MM at the beginning of long trip, if you have to heat up the cabin, using Gen Engine instead of electric range/.
 

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The first time I tried Mountain Mode (with 10 Electric miles left) I was disappointed that nothing happened. I find that I have to pull off the road, put it in Park, then press the accelerator pedal to make MM start. This seems to be a bug. Every time I've switched to MM on the fly it just keeps running down the electric range and the ICE doesnt' start until zero range left. Is there any trick to getting MM started?
 

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The first time I tried Mountain Mode (with 10 Electric miles left) I was disappointed that nothing happened. I find that I have to pull off the road, put it in Park, then press the accelerator pedal to make MM start. This seems to be a bug. Every time I've switched to MM on the fly it just keeps running down the electric range and the ICE doesnt' start until zero range left. Is there any trick to getting MM started?
My experience was that MM won't start immediately but only after about 3miles of driving; the Owners Manual leaves you with impression that MM needs to be activated in advance of really needing it....up a hill ("select MM at least 20mins before driving on steep grade"); I believe that it also infers that if you have EV battery range remaining, that the MM may not come on immediately ("the engine may run when MM is selected, depending on high voltage battery charge,.............").

All this is found on page 9-23 of manual.
 

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My experience was that MM won't start immediately but only after about 3miles of driving; the Owners Manual leaves you with impression that MM needs to be activated in advance of really needing it....up a hill ("select MM at least 20mins before driving on steep grade"); I believe that it also infers that if you have EV battery range remaining, that the MM may not come on immediately ("the engine may run when MM is selected, depending on high voltage battery charge,.............").

All this is found on page 9-23 of manual.
I believe that their point is that if your battery is depleted and you are already using the petrol engine to power the car waiting till you get to the start of the climb is to late. MM needs 20 minutes to build up battery reserve provide you addition power to clime the grade. However If you are at or close to full charge switching to M isn't necessary. Yesterday I took my longest trip and burned .59 gallons of petrol. I burned a lot of volts (small v) without any regard to economy, I had the heat turned up, headlights on rather than running light because it was dark outside at 10:30 AM, wipers on radio on. Eventually I got to one bar and switched to MM. The ICE seemed to be running at a higher RPM then normal then it cycled on and off when the volt meter was at 3 bars. I switched back to normal about 12 miles from home and had depleted the battery without the ICE coming on again, I would call that perfect timing.

When I first got the car I had thought about using the hood switch to trick the car into service mode and get the ICE to run at full charge. After owning the car for a while I discovered it isn't worth the trouble because the car provides sufficient electric heat rather quickly with the temp set at 74, SC winter are mild and even when I do not pre-start the car the cabin is comfortable in less than a mile (about 2 minutes or less). I usually can make 99% of my trips with the heater set at comfort and return home without using the ICE so running the ice at the beginning of my trip would be more wasteful.

Tomorrow will be 6 weeks of ownership and I am glad I burned some petrol because I would rather do it when it is necessary to complete my trip rather than have the ICE come on because the computer decided that it had too long of an interval when the ICE had last run.
 
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