Have you tired performing a search of these forums using the made-up terminology 'chuggle' yet!?

P.S. Whatever you do please don't urban dictionary this very poorly-chosen false term!

 

I believe there is a software fix for this. Yes, "chuggle" is the term being applied to this surging condition.

 

One would think that since the "chuggle" was discovered in 2016, it would not be present in any 2017 models. What am I missing?

 

I have a 2016 Volt built in October 2015. I asked my dealer about the "chuggle" issue, and he told me that my engine was not included in the technical bulletin. I wouldn't think any 2017 models would be affected either.

However, at highway speeds, I notice some "surge" in the drivetrain. Essentially, I find it to be more like the transmission has shifted gears or has a slight hesitation from time to time. This "surge" is not regular or constant, but is noticeable from time to time.

I believe this is related to the drivetrain, but it is not a hardware or software issue. See these two articles on the Gen 2 Volt's drivetrain.

http://www.greencarreports.com/news/1096942_2016-chevrolet-volt-powertrain-how-it-works-in-electric-hybrid-modes

http://www.greencarcongress.com/2015/04/20150423-voltec.html

The Gen 2 Volt has 4 modes of operation in extended range mode. In the high range-extended mode, the ICE is continuously seeking the most efficient point of operation. Sometimes this means it is operating at high power and both driving the car and generating electricity. At other times, it is driving the car and using electricity from the battery.

I did a mathematical model of this transmission, and in the high range-extended mode, the speeds of Motor A and Motor B can be modulated by the power electronics to control the speed of the ICE.

Now we have the ICE, which tries to operate in an Atkinson cycle, but might change from this configuration if more power is demanded. Also, the ICE has external exhaust gas recirculation, which is used to improve efficiency during part load operation. So this engine is constantly changing its load, speed, valve timing, inlet oxygen content, etc. to give the best efficiency.

I believe the "surge" that you are experiencing is related to the changing parameters in the engine and transmission as the system continuously searches for the optimum point of operation.

 

This all sounds logical and plausible even. Could even be true, but I figure that it won't hurt to check with the dealer just to see whether my car would be included in that. I suspect I already know the answer which will be NO because it was built after that October date. But I don't know that for sure. Assuming all that you said is true, and it's normal operation for the car, it's still not a great feeling from the "seat of the pants". Almost makes it feel like the car is having trouble running and gives you the uneasy feeling that it might quit on you at any moment. I can't imagine that GM engineering would settle for that. Especially because, like me, it would unnerve a lot of buyers. Now, with that said, I can and will live with it if need be. But I am going to check it out first before I decide that it's "just the way it is." I had only one problem with my '13 in the 36,000 miles I put on it. And that related to the RKE (remote keyless entry). At about 30,000 miles, it started giving me fits not recognizing that the fob was in the car. I replaced batteries in both fobs, took it to the dealer, they replaced batteries and said it was low battery. I knew that was horse pucky, but I accepted it and went on. Within the week it began doing it again and before I traded the car in, it got to the point where you had about a 50/50 shot as to whether it would start up or not when you got in it. Even refused to unlock a few times, so I began carrying both fobs. My workaround was that if it didn't start, I'd press the unlock button or the remote start button on the fob, and then magically it would decide "oh I guess the fob is in here!" and it would start. Just a PITA to have to drag it out of my pocket most of the time. But at least that car's ICE was smooth as silk!

 

This all sounds logical and plausible even. Could even be true, but I figure that it won't hurt to check with the dealer just to see whether my car would be included in that. I suspect I already know the answer which will be NO because it was built after that October date. But I don't know that for sure. Assuming all that you said is true, and it's normal operation for the car, it's still not a great feeling from the "seat of the pants". Almost makes it feel like the car is having trouble running and gives you the uneasy feeling that it might quit on you at any moment. I can't imagine that GM engineering would settle for that. Especially because, like me, it would unnerve a lot of buyers. Now, with that said, I can and will live with it if need be. But I am going to check it out first before I decide that it's "just the way it is."

Let us know what you find out. There may be some improved software that could even out these transitions, however, that may well have an effect on the EPA rating, which I'm sure GM wants to keep at a maximum.

 

I just bought a used 2017 with 32k miles and yes, I feel that very much on the highway.

 

Most likely chuggle; GM released is an engineering change notice for the Gen2 Volt. The dealer can follow the ECN and apply an update to the Volt's software to reduce the chuggle effect when the ICE is running. Chuggle is most noticeable when the gas engine first starts running, lessens the longer you drive as the gas engine and drive train parts settle down.