[FirstFlight]

Has anyone tried to implement a "long range" mode? I've read some threads on this but couldn't find something that fits the exact question.

People have used MM to do something similar. My thought was to figure out a way to reset the hold mode set point. I've tried it on a few trips and seem to get a 10-15 MPG increase. Recharging the battery with the gas engine reduces the MPG's. The idea would be to simply reset the hold mode set point so it doesn't use any (or very little) gas to recharge the battery. I've been doing this by being in hold mode, then switch back to normal for a few seconds and then back to hold.

It seems to work best for drives that are more than 80 miles. Of course, once the EV range is exhausted, this will no longer work.

Is the mode button on the CAN network? If so, does anyone have the ID? If the reporting isn't very quick, seems like it can be done. It would be perfect if the hold mode set point was a CAN variable. That's exactly what I'd need.

The only thing I haven't had time to figure out is if the switching back and forth reduces efficiency so much that it's not worth it. That's something that can be tested over a few more drives.

 

[kns]

What you suggest is very similar to an idea that was the subject of much heated debate and eventually discredited. Should you wish to immerse yourself in the details take a look at the following very lengthy and tortuous thread.
http://gm-volt.com/forum/showthread.php?222297-Volting-A-Technique-of-Traveling-With-Your-Engine-Off

KNS

 

[saghost]

Has anyone tried to implement a "long range" mode? I've read some threads on this but couldn't find something that fits the exact question.

People have used MM to do something similar. My thought was to figure out a way to reset the hold mode set point. I've tried it on a few trips and seem to get a 10-15 MPG increase. Recharging the battery with the gas engine reduces the MPG's. The idea would be to simply reset the hold mode set point so it doesn't use any (or very little) gas to recharge the battery. I've been doing this by being in hold mode, then switch back to normal for a few seconds and then back to hold.

It seems to work best for drives that are more than 80 miles. If course, once the EV range is exhausted, this will no longer work.

Is the mode button on the CAN network? If so, does anyone have the ID? If the reporting isn't very quick, seems like it can be done. It would be perfect if the hold mode set point was a CAN variable. That's exactly what I'd need.

The only thing I haven't had time to figure out is if the switching back and forth reduces efficiency so much that it's not worth it. That's something that can be tested over a few more drives.

TANSTAAFL. (There ain't no such thing as a free lunch.)

It sounds like you think you're getting some charge in the battery without running the engine harder - which appears to defy the laws of physics as we presently understand them.

The only way recharging the battery with power from the engine can improve economy is if you can shift the engine into a more efficient operating range by doing so - and it has to be enough more efficient to overcome the multiple losses from conversions (mechanical to electric to chemical in the battery and back to electricity and then finally back to mechanical) that the power you're putting in to the battery will have to undergo.

This does happen - but GM engineers are fully aware of where the engine is most and least efficient, and the car is programmed to charge the battery in those cases when it can't just leave the engine off and drive electric.

First generation cars automatically cycled the engine in steady state CS cruising below ~63 mph, slowly charging the battery over 6 or 8 miles, and then turning the engine off and running electric for a mile or so.

I'm not sure if second generation cars do this or not, but I suspect they do in some speed ranges.

 

[rmay635703]

Programming it is very hard.

What I've found on long trips is to leave at least 5 ev miles, then I switch out of hold just before I will have to exit an on ramp or when I assume I will have to slow down, I exit hold when I expect a long downward assent.

Gaming the system this way I can keep the motor off more often and can avoid engine use during a good chunk of city situations.

I never use mountain but I am able to get mid 40's on long trips with zero ev.

 

[srmarti]

Programming it is very hard.

What I've found on long trips is to leave at least 5 ev miles, then I switch out of hold just before I will have to exit an on ramp or when I assume I will have to slow down, I exit hold when I expect a long downward assent.

Gaming the system this way I can keep the motor off more often and can avoid engine use during a good chunk of city situations.

I never use mountain but I am able to get mid 40's on long trips with zero ev.

I do something similar, but I usually start hold mode after 1/4 to 1/2 charge is used. I can do 40+ mpg on my Gen 1. I imagine it would work pretty similar for Gen 2.

 

[voganni]

If your battery is not already full, you can exit hold mode before a long descent, like down a mountain pass. The regen will show an increase in range up to 60 miles on a gen 1. It's not real, but that's as high as the display goes and I've seen it several times. Then re-engage hold after the descent is over and you'll have more ev miles in reserve than before the downhill stretch. The car will do this anyway, in hold, but you won't see the EV miles go up. It will use up the energy it regenerated however before re-starting the engine.

 

[Dutch]

Whenever I read a thread like this, it makes me glad that I used to drive my Jeep to work every day because the efficiency shift from 18mpg MAX and sucking down 38 gallons of gas a week MINIMUM to running about 92% electric and dumping in 8 gallons of fuel every few months was more than satisfying enough. I've got more than enough other things to trigger my OCD without feeling the need to "game" my car's systems.

 

[FirstFlight]

TANSTAAFL. (There ain't no such thing as a free lunch.)

It sounds like you think you're getting some charge in the battery without running the engine harder - which appears to defy the laws of physics as we presently understand them.

Did you read my post? I'm trying to do the opposite - Not recharge the battery with the engine.

Recharging the battery with the gas engine reduces the MPG's.

What you suggest is very similar to an idea that was the subject of much heated debate and eventually discredited. Should you wish to immerse yourself in the details take a look at the following very lengthy and tortuous thread.
http://gm-volt.com/forum/showthread....our-Engine-Off

Thanks for pointing out that thread. My eyes glazed over a few minutes into it but what he's doing isn't what I'm trying to do. There's not many situations where I'd have the engine on with the car not moving. But, every situation is different and if that works for him, then I'd say he's getting what he needs out of his Volt.

What I'm trying to do is a lot simpler and for those who have owned a Gen 2 Prius and installed an extra battery pack, it's very similar to that. To put it a different way, limiting the engine to about 8kW max and not allowing it to recharge the battery would seem to provide an excellent MPG.

The battery will typically give me 43 miles and after the battery is depleted, I typically get about 37.5 MPG as it's mostly highway miles and tend to drive 65-80 MPH. Where I live is 1000 feet above sea level and work is about 50 feet above sea level.

I've driven 80.5 miles today and have about 47.5 more to go (128 total miles - not my normal commute). I left home with a fully charged battery and will not recharge until the car is back home. For this distance, I'd consume the EV battery and probably use about 2.15 gallons of gas.

Today I tried the technique described above and the first two legs of the trip look like this:

Curious to see the final number but I'm guessing the final amount of gas used will be 1.85 gallons and MPG will be around 54. If that holds true, it's an increase of 17 MPG and a gas savings of .3 gallons of gas for the ~130 miles today. I take six 200 mile trips each month and I'm curious if this is reproducible for each trip.

However, this would not be needed on short commutes or charging the battery before the ICE is needed. This technique would work for commutes that are between 80-200 miles? Can't say for sure but once the battery is depleted, all bets are off.

Are there any negatives I'm missing?

 

[saghost]

I did read your post. I'm still somewhat foggy on where you think the extra power for the battery is coming from if not the engine.

Unless I've been misunderstanding the "reset the Hold mode setpoint" and you actually intended to be resetting the set point to a new lower value?

If that's the case, then it sounds like you're trying to blend some battery power into the engine power during cruising?

I'd tend to think that will reduce the overall efficiency since it makes the engine run at a less efficient rate, but the variables are complex enough that this might not be the case.

 

[FirstFlight]

If that's the case, then it sounds like you're trying to blend some battery power into the engine power during cruising?

That's exactly what I'm trying to do. It's much easier with the Prius than with the Volt.

 

[canehdian]

You basically want perpetual ERDTT mode.
It runs at a fixed ~6kW regardless of vehicle demand.
I'd start by analyzing those routines first and see if there are any clues as to what commands make it start at that level and if you can bump that up slightly.
I believe average draw for cruising should be about 12kW.

 

[FirstFlight]

You basically want perpetual ERDTT mode.
It runs at a fixed ~6kW regardless of vehicle demand.
I'd start by analyzing those routines first and see if there are any clues as to what commands make it start at that level and if you can bump that up slightly.
I believe average draw for cruising should be about 12kW.

That seems like what I'm trying to do. If I understand the ERDTT correctly, the engine computer believes the OAT is 15 degrees F?

Can that be done through software or is it strictly a hardware mod?

 

[somms]

That seems like what I'm trying to do. If I understand the ERDTT correctly, the engine computer believes the OAT is 15 degrees F?

Can that be done through software or is it strictly a hardware mod?

If I understand you correctly, U really want constant ERDTT mode!?

If so just gank the OAT sensor off the front of your Volt which creates an open circuit. The displayed temp should default max negative (-40°C/-40°F) and ERDTT should engage immediately. At least this is the behavior on the Gen1 when this sensor is disconnected.

 

[FirstFlight]

If I understand you correctly, U really want constant ERDTT mode!?

Yes, but of course not all of the time.

Awesome! So when the OAT sensor is open, I have ERDTT at a fixed 6kW? If so, I can easily test my theory.

 

[saghost]

Yes, but of course not all of the time.

Awesome! So when the OAT sensor is open, I have ERDTT at a fixed 6kW? If so, I can easily test my theory.

Unfortunately, not that simple. ERDTT will run the engine at low rpm and part throttle when it thinks it is cold outside - until the coolant is warm, then it shuts down until the coolant cools off.

You can certainly spoof a low OAT to initiate ERDTT, but I don't think it'd be wise to spoof the coolant temperature to sustain the mode after the engine warms up.

 

[canehdian]

Unfortunately, not that simple. ERDTT will run the engine at low rpm and part throttle when it thinks it is cold outside - until the coolant is warm, then it shuts down until the coolant cools off.

You can certainly spoof a low OAT to initiate ERDTT, but I don't think it'd be wise to spoof the coolant temperature to sustain the mode after the engine warms up.

Correct. It's easy to start ERDTT to do some testing, but it has programmed upper and lower bounds to run at. You couldn't use it continuously 'out of the box' in the manner described in this thread for more than a couple minutes.
You'd need to make your own way of injecting commands into the system to cause it to run without the coolant temp temp conditions.
I agree that you should not mess with the coolant temp sensor, that definitely has a critical function in the vehicle, unlike the ambient temp sensor.

 

[somms]

Well to be correct removing the OAT sensor and creating and open circuit will cause continuous ERDTT mode regardless of 'cold' or 'very cold' software setting but ERDTT mode inherently only engages the ICE as required...

 

[FirstFlight]

if I had a wish list, it would be for GM to issue another software package to include "blended mode." Having the engine run at max efficiency anytime the accelerator is pressed and then allowing the battery to be used as a buffer for the remaining demand would be a great thing to implement. You'd be slowly draining the battery and getting great MPG's. I wonder what the exact MPG would be once the battery is depleted? 65+? Seems plausible.

 

[saghost]

if I had a wish list, it would be for GM to issue another software package to include "blended mode." Having the engine run at max efficiency anytime the accelerator is pressed and then allowing the battery to be used as a buffer for the remaining demand would be a great thing to implement. You'd be slowly draining the battery and getting great MPG's. I wonder what the exact MPG would be once the battery is depleted? 65+? Seems plausible.

I'm pretty sure there isn't a pony in that hat. The ERDTT operation mode isn't the engine's most efficient - the most efficient operation of the engine is at around 2200 rpm and wide open throttle, producing enough power to move the car down the freeway at ~65 mph.

That's why the first generation cars cycle the engine below that speed - it lets them keep the engine at the most efficient range and pay conversion losses for a small fraction of the power. But as I explained up above, there are tradeoffs in converting the extra power.

If GM's goal was to get the maximum possible gas mileage, it should have had a smaller engine like the i3 one.

GM's goal was to build a convincing electric car that suffers no issues after the battery is drained. So they gave you a slightly bigger engine to assure you had plenty of power even if you drive a few hundred miles at a high freeway speed, and a big battery that should capture your daily driving.

The strategies you're discussing only make sense if the car is starting with a full battery and the car or driver knows it'll be driving beyond the range of that battery - otherwise, you're always better off using electricity.

 

[Insight Refugee]

if I had a wish list, it would be for GM to issue another software package to include "blended mode." Having the engine run at max efficiency anytime the accelerator is pressed and then allowing the battery to be used as a buffer for the remaining demand would be a great thing to implement. You'd be slowly draining the battery and getting great MPG's. I wonder what the exact MPG would be once the battery is depleted? 65+? Seems plausible.

I've been working on the same issue. I discussed my efforts here.

TLDR quote:

The only trick that I use that may be unique is to "reset" the charge hold level if it ever falls below the red line. Like many, I will engage hold mode when I get up to interstate speeds on longer trips (i.e., when I know that I'll easily exceed the electric range). Occasionally the state of charge will dip one segment below the red line while in hold mode. When that happens, I toggle to normal for a short time and then back to hold. In the old Insight, milage would plummet if the battery ever got low enough to enter "Forced Regen Mode". Moving the car and generating extra electricity is an efficiency killer. I can't say for sure that this habit of resetting the hold point is making a huge difference, but I don't think that I'm doing anything else out of the ordinary to get these higher MPGcs numbers.

I'm easily getting well over 50 mpg at 70+ MPH using this toggle method and according to Volt Stats I'm getting better than 97.6% of Volt owners for MPHcs. Like you, I wish GM would have simply included an "endurance" or "blended" mode that capped how much regen the ICE would add to the battery as long sufficient charge remained. I'm pretty sure that the efficiency gained from avoiding extra ICE regeneration exceeds the Normal mode electric miles I'm trading away.

I wonder if CARB regs caused GM to stay away from this mode?