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Discussion Starter #1 (Edited by Moderator)
1st EMM Operation Observations

Some interesting observations I thought I'd share:

1) My first EMM was about 1 month into my ownership

2) FMM stayed on for about 15 minutes total

3) Observed MPG for the ICE showed 86.6 MPG

4) Observed Combined MPGe from start to finish of EMM was 93.3.

5) Total fuel used was reported as 0.03 gallons.

6) Voltstats does not register EMM mode use in calculations it seems. However my MPGcs dropped a tad.

7) You notice the kick when the ICE comes on...it's smooth but not unnoticeable. You do appreciate full EV mode after driving an ICE for sure.

8) Usually when an ICE is parked into a garage after operation and shut down, you tend to smell exhaust gases and engine smells...the Volt had none of that.

So far so good. I hope I can continue to use the car this way without every actually using fuel to operate it.
 

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Some interesting observations I thought I'd share:

1) My first FMM was about 1 month into my ownership

2) FMM stayed on for about 15 minutes total

3) Observed MPG for the ICE showed 86.6 MPG

4) Observed Combined MPGe from start to finish of FMM was 93.3.

5) Total fuel used was reported as 0.03 gallons.

6) Voltstats does not register FMM mode use in calculations it seems. However my MPGcs dropped a tad.

7) You notice the kick when the ICE comes on...it's smooth but not unnoticeable. You do appreciate full EV mode after driving an ICE for sure.

8) Usually when an ICE is parked into a garage after operation and shut down, you tend to smell exhaust gases and engine smells...the Volt had none of that.

So far so good. I hope I can continue to use the car this way without every actually using fuel to operate it.
FMM only ran for 15 minutes? FMM should run until you put at least a half tank's worth of fresh fuel in the tank. Was it perhaps Engine Maintenance Mode instead of Fuel Maintenance Mode?
 

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Discussion Starter #3 (Edited)
FMM only ran for 15 minutes? FMM should run until you put at least a half tank's worth of fresh fuel in the tank. Was it perhaps Engine Maintenance Mode instead of Fuel Maintenance Mode?
I'm sorry did I say FMM? I meant EMM. I'll have to change the subject if I can. But man I do hope FMM doesn't force you to use that much fuel! Isn't defeating the purpose of running in EV mode?
 

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I'm sorry did I say FMM? I meant EMM. I'll have to change the subject if I can. But man I do hope FMM doesn't force you to use that much fuel! Isn't defeating the purpose of running in EV mode?
It does make you burn off the old fuel; if it doesn't, the old fuel can damage the engine and fuel system. It only happens once a year, so it doesn't really impact lifetime mileage that much. It's an unavoidable problem that any vehicle that can accept gasoline will have.
 

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It does make you burn off the old fuel; if it doesn't, the old fuel can damage the engine and fuel system. It only happens once a year, so it doesn't really impact lifetime mileage that much. It's an unavoidable problem that any vehicle that can accept gasoline will have.
It only happens if you haven't added gas to the gas tank. You gotta burn through the gas in 12 months. If you keep a full tank (8.9 gallons), you have to drive 425 ICE miles a year. If you only keep the tank half full; maybe 215 ICE miles a year would be enough.
 

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My dealer filled my tank during the PDI after I told him NOT TOO, so come this Aug I'll probably be forced into a FMM - Arrrrg. I'm currently operating my Gen II Volt at 99.2% all electric. My DD routine right now just doesn't require me to out drive my batteries range to live our lives.

Your observations on the Gen II EMM is spot on with one exception with a Gen I the ICE would start almost immediately after you accepted the screen prompt, with the Gen II it take about a mile of driving before the ICE starts.
 

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I had my first EMM a couple weeks ago. It seemed like while on , the EV miles continued to click downward. Is that normal? IF you have to run the ICE, it should be providing power.
 

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My dealer filled my tank during the PDI after I told him NOT TOO, so come this Aug I'll probably be forced into a FMM - Arrrrg. I'm currently operating my Gen II Volt at 99.2% all electric.
You could always siphon the gas out and use it in your mower, a friend's ICE, etc. Then maybe run the ICE briefly to be sure it readjusts to near empty level. When you add a few litres of fresh gas, it should be good for another interval.

The winter here is cold enough that ERDTT takes care of FMM. I was lucky that the last cold days ran mine to "empty" (0 bars and several warnings) but GOM still said 26km range.

After a few weeks of the daily "please refuel" warning I got tired of it and put half a tank in. I'm going to need it for family visits and vacation this summer anyways.
 

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Discussion Starter #10
I had my first EMM a couple weeks ago. It seemed like while on , the EV miles continued to click downward. Is that normal? IF you have to run the ICE, it should be providing power.
I don't know if that's normal but the overall combined would go down obviously. I settled in at around 94 MPGe combined but was surprised I got such a regular MPG number. It started out at around 38 MPG then climbed up to the 86.6 MPG value for gas only.
 

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I had my first EMM a couple weeks ago. It seemed like while on , the EV miles continued to click downward. Is that normal? IF you have to run the ICE, it should be providing power.
I think it's normal. I've only had one this winter, and it was still mostly EV though cold enough for ERDTT.
It goes through various cycles, which I think only one puts load on the engine, so it can't generate much with motor A.
 

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My dealer filled my tank during the PDI after I told him NOT TOO, so come this Aug I'll probably be forced into a FMM - Arrrrg. I'm currently operating my Gen II Volt at 99.2% all electric. My DD routine right now just doesn't require me to out drive my batteries range to live our lives.

Your observations on the Gen II EMM is spot on with one exception with a Gen I the ICE would start almost immediately after you accepted the screen prompt, with the Gen II it take about a mile of driving before the ICE starts.
FMM would come on anyways; he gave you free gas and prolonged the time it will take for FMM to kick in. The Volt isn't a pure EV. You will have to buy at least 8-9 gallons of gas a year.
 

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FMM would come on anyways; he gave you free gas and prolonged the time it will take for FMM to kick in. The Volt isn't a pure EV. You will have to buy at least 8-9 gallons of gas a year.
When I retire I'll be burning gas on my 2000 mile trips to visit the grand kids. But for now the Volt's range, my DD routine and a level II EVSE just work.
 

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FMM would come on anyways; he gave you free gas and prolonged the time it will take for FMM to kick in. The Volt isn't a pure EV. You will have to buy at least 8-9 gallons of gas a year.
Required annual minimum Volt gas purchase is less than 2 gallons a year.

One way to complete the FMM is to drive until the tank is empty - or sit parked until this happens - and then add the minimum amount of gas (~1.5 gallons). Our friend Ari maintains his 100% ev driving record with his 2012 Volt by completing all gas-consuming procedures while parked (i.e., EMM, FMM, uses a mod to avoid ERDTT). The residual gas remaining in the fuel lines is enough, mixed with the minimum amount of new gas, to have a small impact on the average gas age calculation, and he has noted his FMMs occur ~313 days after the refueling.
 

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Some interesting observations I thought I'd share:

1) My first EMM was about 1 month into my ownership

2) FMM stayed on for about 15 minutes total

3) Observed MPG for the ICE showed 86.6 MPG

5) Total fuel used was reported as 0.03 gallons.

6) Voltstats does not register EMM mode use in calculations it seems. However my MPGcs dropped a tad.

So far so good. I hope I can continue to use the car this way without every actually using fuel to operate it.
Yes, it’s important to distinguish between Engine and Fuel Maintenance Modes (EMM/FMM). One is concerned with keeping the engine running properly. The other is concerned with keeping the engine’s fuel supply fresh.

The EMM can be done while parked, if you want to be sure it won’t count as gas miles. The initial EMM message on the display asks if you want to perform it. The Gen 1 manual says, "If Yes is selected, EMM will begin." The Gen 2 manual says, "If Yes is selected, EMM will begin. The engine will not start until after a short delay once shifted into D (Drive)."

My 2012 Volt also normally reports it uses 0.03 gallons of gas during the EMM. It’s but a small amount of gas, and because that 0.03 gallons usually shows up on the usage screen as Gas Used mid-way through the procedure and well before the EMM is done, a more precise final consumption amount is unknown.

Any attempt to calculate gas mileage during an EMM is likely but a wild guess.

For example, math seems to say that if you got 86.6 MPG (was that actually MPGcs?) while using 0.03 gallons of gas you drove approximately 2.6 miles while using that gas. If that’s done during a 15 minute EMM procedure, you would be averaging ~10.4 mph (while backing out of the driveway? Spending half the time stopped at a stoplight on a city street?).

Perhaps using gas for an EMM while driving doesn’t need to count as Gas Miles. There’s long been uncertainty about this, i.e., if gas is used, should it always be counted as Gas Miles?

MGA is used as the "starter motor" for the Volt’s gas engine, but once the engine is started and if there’s plenty of battery to fuel MGB, perhaps the engine is unclutched from MGA and runs independently to perform the engine maintenance mode procedure. If it’s not contributing to moving the car down the road or generating electricity, even if the engine is running, the distances driven using MGB and battery grid power should count as Electric Miles and the ev range estimate should decrease. You are, in any case, using gas, so your total gas miles / total gas used = MPGcs should change.
 

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I had my first EMM a couple weeks ago. It seemed like while on , the EV miles continued to click downward. Is that normal? IF you have to run the ICE, it should be providing power.
This is normal.
Net result of EMM is electricity used, not generated.
Fuel is only burned for the first portion, the rest is using electricity to keep the engine spinning while adding little to no fuel.
 

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Discussion Starter #17
Required annual minimum Volt gas purchase is less than 2 gallons a year.

One way to complete the FMM is to drive until the tank is empty - or sit parked until this happens - and then add the minimum amount of gas (~1.5 gallons). Our friend Ari maintains his 100% ev driving record with his 2012 Volt by completing all gas-consuming procedures while parked (i.e., EMM, FMM, uses a mod to avoid ERDTT). The residual gas remaining in the fuel lines is enough, mixed with the minimum amount of new gas, to have a small impact on the average gas age calculation, and he has noted his FMMs occur ~313 days after the refueling.
That doesn't seem to be a very efficient way of using fuel that will be used regardless no?
 

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Discussion Starter #18
Yes, it’s important to distinguish between Engine and Fuel Maintenance Modes (EMM/FMM). One is concerned with keeping the engine running properly. The other is concerned with keeping the engine’s fuel supply fresh.

The EMM can be done while parked, if you want to be sure it won’t count as gas miles. The initial EMM message on the display asks if you want to perform it. The Gen 1 manual says, "If Yes is selected, EMM will begin." The Gen 2 manual says, "If Yes is selected, EMM will begin. The engine will not start until after a short delay once shifted into D (Drive)."

My 2012 Volt also normally reports it uses 0.03 gallons of gas during the EMM. It’s but a small amount of gas, and because that 0.03 gallons usually shows up on the usage screen as Gas Used mid-way through the procedure and well before the EMM is done, a more precise final consumption amount is unknown.

Any attempt to calculate gas mileage during an EMM is likely but a wild guess.

For example, math seems to say that if you got 86.6 MPG (was that actually MPGcs?) while using 0.03 gallons of gas you drove approximately 2.6 miles while using that gas. If that’s done during a 15 minute EMM procedure, you would be averaging ~10.4 mph (while backing out of the driveway? Spending half the time stopped at a stoplight on a city street?).

Perhaps using gas for an EMM while driving doesn’t need to count as Gas Miles. There’s long been uncertainty about this, i.e., if gas is used, should it always be counted as Gas Miles?

MGA is used as the "starter motor" for the Volt’s gas engine, but once the engine is started and if there’s plenty of battery to fuel MGB, perhaps the engine is unclutched from MGA and runs independently to perform the engine maintenance mode procedure. If it’s not contributing to moving the car down the road or generating electricity, even if the engine is running, the distances driven using MGB and battery grid power should count as Electric Miles and the ev range estimate should decrease. You are, in any case, using gas, so your total gas miles / total gas used = MPGcs should change.
Well my current MPGcs according to Voltstats is 7.17...it was higher when I first got the car according to Voltstats at around 8.2. The car had 2 miles on it when I picked it up so I can't say whether the dealership or GM used the car in gas mode or not. My current EV% is 99.8% overall but 100% for me since I got the car.

I personally would count the EMM and FMM towards total MPG. The fuel is being used anyway as you say and not counting it torwards energy generation whether it's turning the wheels or charging the battery doesn't make sense to me.

My EV MPG did drop dramatically when the EMM initiated but the two (MPGe and MPG) settled to with 7-8 units away from each other. I did only travel a short distance as it was brief open freeway then stop and go.
 

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Discussion Starter #19
This is normal.
Net result of EMM is electricity used, not generated.
Fuel is only burned for the first portion, the rest is using electricity to keep the engine spinning while adding little to no fuel.
This suggests that the plugs aren't firing?
 

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This suggests that the plugs aren't firing?
I won't pretend to know what's going on inside the engine, but you can see with OBD that the fuel injector flow is cut to almost nothing and the electricity flow from the motor switches from negative (generation) to positive.
I haven't heard a gen2, but it's also audibly different in a gen1 when it switches over (yet the RPMs stay the same).
 
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