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I having a daily commute of approximately 165km round-trip. As I drive I wonder: should I drive in normal mode and hold power on highway? Or is it more efficient to drive on normal mode till the battery is gone and switch to mountain mode for short-term battery charging for future city driving.

The options are not self evident on their face. Mountain mode driving at highway speeds increases the throttle, and hence fuel consumption, more than normal driving but is driven for a shorter duration. Normal mode has lower engine RPM, but for longer duration (also it uses the battery at times and charges it in the future).

I propose and experiment: what is better for an extended drive? Mountain mode or Normal/hold?

I have a daily total commute of 165km with no intermediate charge points. It involves the following:
1) 3 km at 60kph (city driving)
2) 3.2 km at 70kph
3) 14.5 km at 90kph
4) 51.5 km at 115kph
5) 1.3 km at 80kph
6) 17 km at 50/60kph (city driving)
7) 1.1 km at 80kph
8) 51.5 km at 115kph
9) 15 km at 90kph
10) 3.4 km at 70kph
11) 2.9 km at 60kph (city driving)

Every other day I will alternate between mountain mode driving and normal/hold driving. This will be an attempt to mitigate weather, road, and time of year effects.

Mountain mode driving will be leaving my house at a full charge, driving on normal until the batteries die, drive on mountain mode until 60kph zone (the battery is charged to three bar where the city driving occurs), switch back to normal city driving, switch back to mountain driving when back on highway until 50% charged or reaching the 90kph zone, then switch to normal until back home.

Normal hold driving will be leaving home at a full charge, driving on normal until reaching 90kph where will put on hold until arriving at 60kph (city driving) where switch back to normal. Drive normal until back at 80kph where switch back to hold. Drive on hold until I can reach home on battery (based on gps estimates) where switch back to normal and drive on battery until it dies.

Hypermiling techniques will be: 1) switching to low gear when decelerating and not apply break unless absolutely having to, 2) accelerating using cruise control setting, 3) driving on Eco mode climate control, 4) 42psi on winter tires

Days / Mountain mode or Normal hold / L per 100km / fuel used in Litres
00/baseline normal mode/5.21/8.63
01/MM/4.90/8.13
02/NH/4.72/7.88
03/MM/4.98/8.25
04/NH/4.78/7.88
05/MM/5.1/8.75
06/NH/4.55/7.50
07/MM/4.98/8.38
08/NH/4.98/8.13
09/MM/5.38/8.88
10/NH/4.85/8.00
11/MM/5.03/8.38
12/NH/4.93/8.25
13/MM/6.06/10.25
14/NH/5.24/8.63
15/MM/5.08/8.38
16/NH/5.21/8.63


Mode; Average L/100km; Average L used; Std dev L/100km; Std dev L used
MM; 5.18875; 8.675; 0.38; 0.68
NH; 4.9075; 8.1125; 0.24; 0.39

So overall it looks like Normal Hold is more efficient that just plain normal and normal/mountain mode switching based on my driving schedule. Overall though it doesn't seem like a huge savings.

As an aside one thing I noticed is that the mileage reporting did not directly line up with gas used. The actual km driven never changed but the mileage changed even with the same fuel burn (check out last two NH runs)














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This has been a subject of heated discussion since the Volt first came out, subject to numerous threads with varying degrees of rationality and science. You do appear to have collected more data than most initial posts on the subject. :)
 

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There's a common misconception that driving in L is more efficient than "coasting" in D prior to a stop. It is not. Regenerative braking involves conversion losses to charge the battery, while the only losses in coasting are due to wind and rolling resistance (which you also have in L). This is just physics, not an opinion.

So, bottom line is that in light traffic, where you have room to coast, driving in D will net you better mileage than with driving in L. That said, I almost never drive in D because the driving experience is much better in L and I drive very aggressively...so blended/friction brakes are almost always involved in most of "my" braking situations.
 

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The ROI is not worth it. Way to much in investment in time and thought compared to just driving and enjoying it.

Just drive it. Use Hold Mode (HM) on the HWY to save a few EV miles for driving around town. Use Mountain Mode (MM) to build a few miles for around town if needed. City driving is more enjoyable without the ICE running. Running the ICE on the HWY is much less noticeable.
 

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Interesting. Of course, how it works depends on the terrain. I don't think anyone is arguing that using MM on a flat highway is going to be efficient.

What if it was used only where there was more "free energy" to be harvested? Seems to me that if you have a long descent into work and you're driving with a full battery, there's no place for the regen feature to put the saved energy, so where does it go? Does regen cut out when the battery is full?
 

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There's a common misconception that driving in L is more efficient than "coasting" in D prior to a stop. It is not. Regenerative braking involves conversion losses to charge the battery, while the only losses in coasting are due to wind and rolling resistance (which you also have in L). This is just physics, not an opinion.

So, bottom line is that in light traffic, where you have room to coast, driving in D will net you better mileage than with driving in L. That said, I almost never drive in D because the driving experience is much better in L and I drive very aggressively...so blended/friction brakes are almost always involved in most of "my" braking situations.
Since my MPG is 250+, it has become a boring waste of display in my DIC. So I've been displaying the MPGe data instead and observing how the value changes per my driving habits.

Driving in D if I coast to a stop, apply gently the breaks for the full stop, I get lower MPGe than applying the paddle wheels at appropriate distance then the brakes for the full stop. Using the paddle wheels while in D and through the city traffic, my MPGe is always higher than coasting and braking to each stop or than driving in L. I believe that I will end up with the same MPGe for various driving styles if I find their sweet spot combination that gives me the highest MPGe. I have found it in D and using paddle wheels combo. Will try to find it in L.
 

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Since my MPG is 250+, it has become a boring waste of display in my DIC. So I've been displaying the MPGe data instead and observing how the value changes per my driving habits.

Driving in D if I coast to a stop, apply gently the breaks for the full stop, I get lower MPGe than applying the paddle wheels at appropriate distance then the brakes for the full stop. Using the paddle wheels while in D and through the city traffic, my MPGe is always higher than coasting and braking to each stop or than driving in L. I believe that I will end up with the same MPGe for various driving styles if I find their sweet spot combination that gives me the highest MPGe. I have found it in D and using paddle wheels combo. Will try to find it in L.
You're talking about a complete different issue than MM vs. Hold. I have found that coasting like the dickens in D is better than L (and presumably paddle regen). Remember, momentum is your friend. As I'm approaching a stop light, I tend to coast like crazy and sometimes I get lucky, the light turns green, and I never have to touch the brakes.

When I drove in L, I tended to stay on the accelerator until the exact point when I lift the accelerator and heavily regen to come to nearly a stop. I found that my Ev range would drop driving in L vs. D because I was staying on the accelerator longer. Sure you could feather the accelerator to achieve whatever dynamic you wanted, but it was easy to be all on or all off.
 

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You're talking about a complete different issue than MM vs. Hold. I have found that coasting like the dickens in D is better than L (and presumably paddle regen). Remember, momentum is your friend. As I'm approaching a stop light, I tend to coast like crazy and sometimes I get lucky, the light turns green, and I never have to touch the brakes.

When I drove in L, I tended to stay on the accelerator until the exact point when I lift the accelerator and heavily regen to come to nearly a stop. I found that my Ev range would drop driving in L vs. D because I was staying on the accelerator longer. Sure you could feather the accelerator to achieve whatever dynamic you wanted, but it was easy to be all on or all off.
I was just responding to your theory about coasting in D versus paddle wheel or L. My observations doesn't support it by watching how my MPGe scores changes as a response. In fact I get better scores with D and paddle wheel than coasting. Have you watched how your MPGe scores vary for the trip? Theory should be validated by observations, but in my case, the opposite seemed to be happening. In disparities like this, we either need to do a careful study with careful observations or suspect that the MPGe calculations might be wrong, or perhaps it can be the Gen 1 vs Gen 2 thing, as I have observed this in Gen 2 and just noticed the thread is about Gen 1.
 

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Interesting. Of course, how it works depends on the terrain. I don't think anyone is arguing that using MM on a flat highway is going to be efficient.

What if it was used only where there was more "free energy" to be harvested? Seems to me that if you have a long descent into work and you're driving with a full battery, there's no place for the regen feature to put the saved energy, so where does it go? Does regen cut out when the battery is full?
You may not have seen it, but many folks have argued precisely that, including the character that attempted to name the method "Volting" and treated it like his own invention despite coming in years after the initial debates.

The idea that it could be more efficient on the flat isn't totally without merit - committed hypermilers in the Prius do get much better mileage from the Pulse and Glide technique than they could from driving at a steady speed at the stage of the PnG - mainly because it allows the engine to operate more efficiently. The Volt does this internally in any drive mode, however, so the argument didn't work out.

In answer to your other question, GM allows regen to fill a couple hundred Wh above the highest it will ever charge from the wall, so most owners will never run out of room for regen.

If you do, though, first generation Volts go into 2 motor EV or Power Split and then dissipate some of the excess energy as great by driving both motors to high load, one as a motor and the other as a generator. It isn't as strong as normal regen, and obviously you're losing all the energy and pushing the motor cooling systems.

I'm not for what a second generation car will do - possibly something similar?
 

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The ROI is not worth it. Way to much in investment in time and thought compared to just driving and enjoying it.

Just drive it. Use Hold Mode (HM) on the HWY to save a few EV miles for driving around town. Use Mountain Mode (MM) to build a few miles for around town if needed. City driving is more enjoyable without the ICE running. Running the ICE on the HWY is much less noticeable.
I concur. Hold mode on the highway and normal on city streets when possible.

Other than that, save the analysis paralysis and enjoy.
 

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snip...

If you do, though, first generation Volts go into 2 motor EV or Power Split and then dissipate some of the excess energy as great by driving both motors to high load, one as a motor and the other as a generator. It isn't as strong as normal regen, and obviously you're losing all the energy and pushing the motor cooling systems.

I'm not for what a second generation car will do - possibly something similar?
Walter, I've been dying to get to the bottom of this... I've read several places about what you say above, yet WOT was emphatic here that that does not happen. When even the experts disagree, I don't know what to do :p
 

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Discussion Starter #13
I appreciated that a flame war hasn't started. I just got my Gen1 Volt in January and saw that there could be a difference (the engineer in me says measure/fiddle with it). I've never heard of "volting" so I'm going to have to read up on that.

During the past month I have observing some interesting side notes:
1) When switching to hold mode, initially the engine engages at the same RPM as mountain mode for a few minutes. Then it settles out at a lower cruise rpm. I'm assuming that this is to warm engine coolent.
2) When switching from normal to MM on highways, the engine nearly maxes its rpm for a minute or so. To mitigate this, I would switch back to normal and back to MM, and it would go away (lower rpm mode).
3) Although I'm not in a hilly terrain (aside from on-ramps), I am in a very windy area, I find that tail and head winds don't seem to affect the volt much, but a quartering crosswind greatly affects the mileage (my highest mileage day was during a strong quartering cross/headwind)
4) I found that the numbers of MPG & fuel burn did not always collaborate. I wouldn't put a huge reliance on them as I suspect measurement bias error.
5) My initial mileage reports were better than my final mileage reports. As being in Canada I started driving in January at -10C and ended in a warm mid Feb at +15C. I suspect that the degradation of mileage being winter-tire softening issues above +6C.
6) I should mention that I was using top tier regular (86 Octane) gasoline rather than premium. The price difference of premium in Canada does not offset the improvement in mileage.

To weigh into the coast vs regen, regen by definition is less efficient as you sustain energy conversion losses (kinetic, to electrical, to heat of component). I don't believe that the volt has an ultracapacitor bank (correct me if I'm wrong) so you have hysteresis losses, electrical line losses to the inverter, inverter losses, electrical line losses to battery, battery chemical losses. Then the additional conversion losses when you reverse the process by stepping on the gas pedal. (although I'd rather have those losses in sport/low mode, fun driving around town)

As a general observation, I'm only observing four throttle levels (idle, top of inital ramp, 3/4, full throttle). Is anyone experiencing other throttle levels? I'm wondering if a diesel turbine conversion would be more efficient due to lack of continuous power curves. Turbines are a order of magnitude more efficient as there is only one "moving" part rather than a complete ICE drive train.
 

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The ROI is not worth it. Way to much in investment in time and thought compared to just driving and enjoying it.

Just drive it. Use Hold Mode (HM) on the HWY to save a few EV miles for driving around town. Use Mountain Mode (MM) to build a few miles for around town if needed. City driving is more enjoyable without the ICE running. Running the ICE on the HWY is much less noticeable.
I'd have to agree...incredible amounts of effort for little gain. If it's a hobby of some sort to occupy oneself, I get it....but beyond that...
 

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Walter, I've been dying to get to the bottom of this... I've read several places about what you say above, yet WOT was emphatic here that that does not happen. When even the experts disagree, I don't know what to do :p
I have a great deal of respect for WopOnTour, and he has access to GM technical documents that the rest of us don't.

Having said that, I have actually seen the car do this on a DashDAQ. Unfortunately I only saw it a couple times and didn't manage to log it - unless you have access to a charger near the top of a big hill it's hard to get into.

My 2012 definitely did use this technique to slow the car with a full battery in L on two occasions; I generalized that to the assumption that all first generation cars will use it at any time that regen is called for and the top buffer is full.
 

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The ROI is not worth it. Way to much in investment in time and thought compared to just driving and enjoying it.

Just drive it. Use Hold Mode (HM) on the HWY to save a few EV miles for driving around town. Use Mountain Mode (MM) to build a few miles for around town if needed. City driving is more enjoyable without the ICE running. Running the ICE on the HWY is much less noticeable.
My thoughts exactly.

While I love driving efficiently. I also enjoy being able to just cruise without having to worry about using too much energy/fuel.
 

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regarding 'hold mode on highway, electric around town' this also is not a black and white picture.

it depends whether or not you can make it to your destination on all electric.

all electric to work & electric/gas to home is better gas mileage (for me)

than electric/hold to work & electric/gas to home.

In other words, using gas once (return trip only) is more efficient than using gas twice (using hold/mountain mode to work) and (remaining electric + sustain mode).

starting and warming up the ICE twice, is less efficient than starting and warming it up once.

The other side is, if you are on a longer trip than your all electric range, you may be better off with hold/MM while on the highway to save electric for in destination city traffic.
 

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regarding 'hold mode on highway, electric around town' this also is not a black and white picture.

it depends whether or not you can make it to your destination on all electric.

all electric to work & electric/gas to home is better gas mileage (for me)

than electric/hold to work & electric/gas to home.

In other words, using gas once (return trip only) is more efficient than using gas twice (using hold/mountain mode to work) and (remaining electric + sustain mode).

starting and warming up the ICE twice, is less efficient than starting and warming it up once.

The other side is, if you are on a longer trip than your all electric range, you may be better off with hold/MM while on the highway to save electric for in destination city traffic.
Well, even that depends on how cold it is outside.
 

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On longer trips (spring/summer/fall), exceeding the range of the battery, I like to start out in MM. It's like starting out in Normal mode until the battery is about half depleted and then the engine begins. But I find that the engine runs with less RPM variations and pulls from the battery when needed (various hills).

Normal mode tends to run at higher RPMs and banks energy (more so on rural highways vs interstate driving), shutting the engine off completely at times and starting again later.

Just my experience. :)
 

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I have a 2015 volt premium I bought new in 2015
When I travel to tampa,FL every few month's, I use electric in town and ice outside of town and on the interstate.
I get 47 mph while in hold mode
This works for me
I have tried mountain mode, it only gives me 27 ev miles total, it is more efficient to be in hold mode outside of town, as whatever battery you have when you switch into hold mode, my volt maintains that level until I switch back into normal mode
 
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