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Discussion Starter · #1 · (Edited)
Say you are on a trip, and battery is zero.

You enter MM and generate the battery. Then switch to Normal until the battery is done. Go to Mountain Mode again. Repeat.

Would you be able to travel a greater distance than by just using Hold Mode gas?
 

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that really depends on alot of factors. I regularly use MM when I'm on the highway on level ground to save the battery for the long grades at the end of my commute, the idea being that my MPG is better on the flat than it would be on a hill or in my neighborhood at the end of my trip.

But in my experience, MM causes the engine to rev higher than it would normally(i hear it, anyway) and the engine doesnt shut off in traffic while charging, it stays at high RPM.

So i would think the most efficient possibility for charging would be at highway speeds, since the engine is on anyway. the only real question is, in just a 'highway miles' scenario, is the extra fuel required to charge the battery while moving the car more efficiently used charging the battery or moving the car?

i think the answer is in the complicated drivetrain, which sometimes is just charging the battery, and sometimes connected to the wheels directly. The engineers knew that at some point at highway speeds, it becomes *more* fuel efficient to run the car like a regular mechanical ICE/drivetrain setup, than to just use the engine to charge the battery.

By that logic, at highway speeds alone on a long trip, i would surmise you're better off NOT in MM.
 

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I doubt it. There is no free lunch. The energy consumed in Mountain Mode to charge the battery in the form of burning extra gasoline will be greater than the energy you can get back out of the battery. It has to be due to losses and efficiencies. Just leave it in Normal and let the system do its thing, or switch to Hold on the highway if you want to reserve some battery range for low-speed driving.
 

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Say you are on a trip, and battery is zero.

You enter MM and generate the battery. Then switch to Normal until the battery is done. Go to Mountain Mode again. Repeat.

Would you be able to travel a greater distance than by just using Hold Mode gas?
I've tried this... the amount of 'charge' is only about 50%, and then the ICE backs way down. I did notice that if you switch to MM *after* the battery shows Zero, and the ICE kicks in automactically, you won't be able to switch 'back' to normal mode. You would need to change to MM with about 3 miles of battery remaining.
 

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Say you are on a trip, and battery is zero.

You enter MM and generate the battery. Then switch to Normal until the battery is done. Go to Mountain Mode again. Repeat.

Would you be able to travel a greater distance than by just using Hold Mode gas?
TANSTAAFL - there ain't no such thing as a free lunch. In this case, what that means is that the "extra/free" battery charge comes because the engine is staying on longer or running at higher RPMs (or both.) All other things being equal, you're burning the same amount of gas as Hold mode, just compressing it into shorter periods.

Actually, though, all other things aren't equal, and so the full answer is complicated. There is a single point at which the engine is theoretically most efficient - in our case it appears to be about 1700 RPM and WOT (the engine generally runs at WOT in the Volt, which is a good thing.) Operating at any other point is less efficient, and the further away, generally the less efficient it gets.

On the other hand, there is a price for putting power into the battery and taking it back out, too - you don't get all of the power back. I don't have an exact round trip number for the Volt - it should be somewhere between 0 and the ~16% loss that we see from the wall (because that 16% includes AC/DC conversion, running the TMS (though not the heater or A/C elements, which eat a bunch more power,) and computers to monitor things over the length of the charge.)

So the answer is that in theory, if you can run Mountain mode only at a time when it will move the engine into a more efficient range and gain enough efficiency to balance the battery round trip losses, you can gain some mileage this way. Or you can lose mileage by pushing the car further off optimal and incurring unneeded battery cycles.

When folks tried it a few years ago (try searching for Mountain Mode games) we saw results from +10% to -10% depending on the driver and details of their test, with most showing no gain or a slight loss - though few were really adequately controlled for a truly valid answer.
 

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Whenever I go on a long distance trip I you know I am going to use gas anyway.. I used MM right away at full charge. The engine don't rev up too high and the battery stays half full. I used MM all the way to my trip and I get 45 - 50 mpg.
 

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Every time I try to game MM or HM I am less efficient than Volt's programming. I just drive and let the 10M lines of code figure it out.
 

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Discussion Starter · #10 ·
We all know those Laws of Thermodynamics, right?

But I was wondering if. gas + friction & heat = MPG 1 is different than

Gas + MM Charge + friction & heat = MPG 2

and if MPG 2 might be more miles MPG1

We will do a trip from Snowville, UT to Ontario, OR which is pretty flat next spring. That might provide a good test as long as the wind condition is fairly calm.
 

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If I understand your procedure, then I think the answer is no. In fact I think what you are proposing would decrease total range, because your "gaming" strategy likely will waste energy (i.e., generate more heat).

That said, I always game MM on a long trip in my 2011 Volt. I save EV miles for stop and go driving by engaging MM on the highway. That way the ICE generally operates near peak efficiency, and I can't ever hear it! P.S. I'm also careful to arrive at my destination with a fully depleted battery. Otherwise it makes no sense.
 

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We all know those Laws of Thermodynamics, right?

But I was wondering if. gas + friction & heat = MPG 1 is different than

Gas + MM Charge + friction & heat = MPG 2

and if MPG 2 might be more miles MPG1

We will do a trip from Snowville, UT to Ontario, OR which is pretty flat next spring. That might provide a good test as long as the wind condition is fairly calm.
In general, no, because there are more inefficiencies involved with charging and discharging the battery. There are some exceptions mapping to very specific terrain profiles on a particular trip, but some repeated use of MM to turn off your engine more is almost always less efficient due to these charging/discharging efficiencies.
 

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You don't need to know the laws of physics, because the Volt has been engineered to already account for them. The absolute most efficient way to drive the car for any particular terrain is in Normal mode, keeping the green ball in the center. Use the battery up first and then let the ICE provide the electricity to the motors. You cannot game the battery and ICE combination. Others have explained the scientific reasons why.
 

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You don't need to know the laws of physics, because the Volt has been engineered to already account for them. The absolute most efficient way to drive the car for any particular terrain is in Normal mode, keeping the green ball in the center. Use the battery up first and then let the ICE provide the electricity to the motors. You cannot game the battery and ICE combination. Others have explained the scientific reasons why.
I agree with everything you said except for the battery first part. If you are traveling further than your AER, then you are better off using gas during the high speed portions of the trip where the car can run in parallel-hybrid mode. Of course, you need either hold mode or entering mountain mode with greater than the larger buffer of battery left to do that.
 

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Here's the simple answer:

No, no way!

The reason: When you plug in your Volt, it takes 13 kwh to charge the battery to 10 kwh. There is a 15 to 20% loss of energy when you charge the battery. For that reason, it is better to generate and use the electric power in one step rather than store it in the battery and use it later.
 

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Here's the simple answer:

No, no way!

The reason: When you plug in your Volt, it takes 13 kwh to charge the battery to 10 kwh. There is a 15 to 20% loss of energy when you charge the battery. For that reason, it is better to generate and use the electric power in one step rather than store it in the battery and use it later.
Okay, I don't understand your logic. Are you saying that Hold Mode (and/or MM) are useless from an energy-saving perspective? If so, I humbly disagree. There are opportunities to preserve EV miles and use them to better advantage, like in stop-and-go traffic.

By the way, there is nothing magical about the 15-20% energy loss. It all goes to waste heat. First Law of Thermodynamics.
 

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Here's the simple answer:

No, no way!

The reason: When you plug in your Volt, it takes 13 kwh to charge the battery to 10 kwh. There is a 15 to 20% loss of energy when you charge the battery. For that reason, it is better to generate and use the electric power in one step rather than store it in the battery and use it later.
You are correct ... assuming the efficiency is the same between the electricity generation methods. However, that's definitely not the case when you compare efficiency of the grid versus even the best ICE. You have to include the energy waste from the beginning to the end, not just the last couple of steps. There is also lost efficiency in the amount of energy in the source fuel to create the 13kW from the grid to generate 10kW from the battery. But it's nowhere near the efficiency loss to go from gasoline to create electricity off an ICE.
 

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I agree with everything you said except for the battery first part. If you are traveling further than your AER, then you are better off using gas during the high speed portions of the trip where the car can run in parallel-hybrid mode. Of course, you need either hold mode or entering mountain mode with greater than the larger buffer of battery left to do that.
I doubt that's true because you are assuming the ICE in the Volt acts the same as an ICE that directly propels a standard car. It doesn't work that way. The ICE in the Volt doesn't immediately have to respond to peak energy demand to the wheels. Instead, it balances the level of electricity needed plus the amount of electricity needed to sustain the defined SoC in the battery. Peak energy demand doesn't only come from the ICE. It can be supplemented from the battery (hence the purpose of MM in one specific situation). That's why pressing down on the accelerator doesn't directly equate to the ICE's RPMs.

I seriously doubt you can game that efficiency except in some very limited circumstances.
 

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I doubt that's true because you are assuming the ICE in the Volt acts the same as an ICE that directly propels a standard car. It doesn't work that way. The ICE in the Volt doesn't immediately have to respond to peak energy demand to the wheels. Instead, it balances the level of electricity needed plus the amount of electricity needed to sustain the defined SoC in the battery. Peak energy demand doesn't only come from the ICE. It can be supplemented from the battery (hence the purpose of MM in one specific situation). That's why pressing down on the accelerator doesn't directly equate to the ICE's RPMs.

I seriously doubt you can game that efficiency except in some very limited circumstances.
I'll bite. Why do you think GM provides Hold Mode in the first place? And why do you think some members here were so upset when they couldn't get it as a software upgrade? (I know there are secondary answers related to cabin heating and silent running...)

I believe folks here at gm-volt.com have reported better MPG when they use Hold Mode (or properly game Mountain Mode). That's certainly my experience. Definitely, in Extended Range mode, in city traffic, there are times when the ICE goes into fairly high revs. Also, the ICE turns on and off quite frequently. Stop and go traffic is not the best use of the ICE. In contrast, on the highway at steady speed, the ICE runs essentially continuously at modest revs. This is an efficient use of the ICE.

Am I missing something in your statements?
 

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Why do you think GM provides Hold Mode in the first place? And why do you think some members here were so upset when they couldn't get it as a software upgrade? (I know there are secondary answers related to cabin heating and silent running...)
On the first one, we know Hold Mode was standard on EU-bound Volts and Ampera's even in 2012. I believe it was a mandated EU feature. The motivation for leaving it out or adding it in to the US/CA models is beyond my knowledge. I would conjecture that in the EU there's probably some thinking in terms of places where you might not be permitted to use an emissions vehicle. Perhaps they added it to all the versions because they realized it made no sense to have a difference. Who knows?

As you and I know, measuring how upset people on forums are about any particular thing doesn't tell you much more than they are upset about that particular thing. Far be it from me to tell you or anyone else that you are or are not getting better MPG by managing the running of the ICE at particular times. I suspect that it's a very limited situation and, for the vast majority of Volt drivers, they get the optimum efficiency by leaving it in Normal Mode.
 
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