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Discussion Starter · #1 ·
So I'm at the dealer today in the hope they will update the backfire issue. The SA said it takes a long time (to hook the thing to a computer and walk away???). Anyway, I drained the battery so if they had to go for a joy ride they could experience the issue quickly. I got to wondering with my drained battery about how long the AC would run on almost no battery while sitting at a traffic light. I know a lot of start/stop cars will start the engine after a minute or so sitting with the AC on. So how long will the Volt be able to run the AC at a light if there is effectively no battery left before it starts the engine?
 

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The car uses about a kilowatt hour of battery as working buffer for the engine, and at the start of your time at the light you'll likely be near the top of that. I don't think it'll let you spend the whole thing on A/C, since that would mean poor acceleration, but I think it does allow ~300 Wh before cycling. That's around 3 minutes of 6 kW full load initial cooling the car on a really hot day, or close to twenty minutes of 1 kW keeping the car cool in typical summer conditions.
 

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I have no Volt but I expect that it can run for minutes, depending on the heat load (temperature difference).

Did you check the Volt owner manual? I believe that you can run the Volt's gas engine while parked for testing by opening the hood. Then if the backfire happens the dealer can catch it while under test.
 

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Discussion Starter · #4 ·
I have no Volt but I expect that it can run for minutes, depending on the heat load (temperature difference).

Did you check the Volt owner manual? I believe that you can run the Volt's gas engine while parked for testing by opening the hood. Then if the backfire happens the dealer can catch it while under test.
I already had a TAC case open with GM, so they shouldn't have to do anything. But then again, I never trust dealerships to do anything right/sensible.
 

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Discussion Starter · #5 ·
Success! They actually reprogrammed the PIM according to the TSB, they didn't have to take a joy ride, I haven't heard a backfire yet, and I have to admit that the EV to ICE transition does seem smoother. The engine remains buzzy, and though it might just be my imagination, it seems a little less so now.
 

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I don't recall my engine ever starting up at a traffic light to provide power for the A/C, or for any other reason, so whatever buffer they have for that seems to last through traffic lights, at least in my experience.
 

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I don't recall my engine ever starting up at a traffic light to provide power for the A/C, or for any other reason, so whatever buffer they have for that seems to last through traffic lights, at least in my experience.
In frigid temps if I've just recently run out battery and the ICE has not yet warmed up enough to provide waste heat for the cabin, it can be drawing 8 kW for heat at a stoplight. Once or twice at this stupidly long stoplight along my commute the ICE had to kick in. But that's been very rare.
 

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I don't recall my engine ever starting up at a traffic light to provide power for the A/C, or for any other reason, so whatever buffer they have for that seems to last through traffic lights, at least in my experience.
Stoplights aren't that long, regardless of how they seem.* The buffer at CS mode is big enough to power the heating for about five minutes at full blast from engine shutoff to needing to start it again, and if the cabin is already comfortable, it could easily manage 15 minutes.

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* Generally accepted traffic planning has signals change from red after no more than 100 seconds and between 60-90 seconds are recommended from a side street into an arterial.
 

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Stoplights aren't that long, regardless of how they seem.* The buffer at CS mode is big enough to power the heating for about five minutes at full blast from engine shutoff to needing to start it again, and if the cabin is already comfortable, it could easily manage 15 minutes.

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* Generally accepted traffic planning has signals change from red after no more than 100 seconds and between 60-90 seconds are recommended from a side street into an arterial.
The traffic lights in MD, DC and especially Northern VA are whole different trip. I believe that one traffic signal in Fairfax, VA was timed to have a cycle that is 7 minutes long.
 

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The traffic lights in MD, DC and especially Northern VA are whole different trip. I believe that one traffic signal in Fairfax, VA was timed to have a cycle that is 7 minutes long.
I can imagine lots of people give up after way less time than that and just drive through the light - Do they have a cop posted nearby to fill the city's coffers by writing tickets??

Don
 

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I can imagine lots of people give up after way less time than that and just drive through the light - Do they have a cop posted nearby to fill the city's coffers by writing tickets??

Don
No cop usually, just long lines of vehicles. red-lights-that-try-the-soul
 

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I can imagine lots of people give up after way less time than that and just drive through the light - Do they have a cop posted nearby to fill the city's coffers by writing tickets??

Don
Yeah, I think I'd wait 5 minutes and after that, I'd assume the lane sensor was broken and just pick a time when I know it's safe (obvious break in traffic, no cops, no red light cameras) and I'd drive through it. I've never seen one around here longer than about 2.5 minutes.

Mike
 

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Yeah, I think I'd wait 5 minutes and after that, I'd assume the lane sensor was broken and just pick a time when I know it's safe (obvious break in traffic, no cops, no red light cameras) and I'd drive through it. I've never seen one around here longer than about 2.5 minutes.

Mike
You might be able to jump the light between 0100 and 0400 but the other 20 hours a day the opposing traffic would prevent you from moving through the intersection. There are traffic cameras to monitor traffic flow in real time, not sure if there are also red light violation cameras.
 
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