Holes 1-4-6- and 7 are the designated AFM cylinders.The dumped cylinders are not rotated. Read up here. http://www.autobytel.com/car-ownership/ ... rs-104039/

Holes 1-4-6- and 7 are the designated AFM cylinders.The dumped cylinders are not rotated. Read up here.

http://www.autobytel.com/car-ownership/ ... rs-104039/

Thanks Obrian....Personally i just would rather prefer all my vavles and cylinders be working all the time at the same time thus more even wear. just sayin!

GoAudio wrote:Thanks Obrian....Personally i just would rather prefer all my vavles and cylinders be working all the time at the same time thus more even wear. just sayin!

Me too.

All pistons always move in V4 mode, there is only one crankshaft and no way to disconnect it from the unactivated cylanders. The engine computer shuts off fuel and spark to the deactivated cylanders (easy to do in today's electronically controlled engines) and adjust the valve assembly to keep them closed so the pistons bounce against an air "spring" and get a little downward help. This last part is the mechanical portion of the system and probably the most complicated part. (But then I find computers and software easy.) So operating wear should be just about the same.

I have noticed in cold weather the engine will not go into V4 mode until it reaches a minimum temperature. There is a long slightly downhill road on the way to work just outside my neighborhood. In warmer weather the engine will go into V4 mode quickly since its hitting the minimum temp by the time I leave the neighborhood. However in these colder months V4 doesn't engage until I'm well past that road. Saying that V4 mode is bad for a cold engine is probably correct but the computer won't activate it before its ready. So its really a non-issue.

From the software point of view, accurately coordinating fuel injection and and spark generation at the right moments of piston position is not a trivial task. Deciding not to activate a V4 mode if coolant temp is less than x degrees, that's super easy.

It would be a great system if they would have programmed it to kick in after 40-50 mph. Any lower than that and it feels like your lugging the engine. Mine goes into v4 at all speeds once up to temp. Yes I know you can use M5 to stay out of v4 mode. I called service department and asked if they could change it and they basically said your S.O.L

Yea, GM dropped the ball when they established the parameters at which AFM is activated. At slower around town speeds it doesn't stay activated long enough to justify its design intent when a mere hint of the throttle kicks it back into 8 cylinder.GM needs to acknowledge and rectify this design flaw.Consumers aren't stupid. No wonder so many people want to disable the system.

I see a lot of incorrect information in this thread about AFM. I thought by posting the AFM parameters in here might help some folks understand how it works and what the parameters there are that can be set or changed.

I appreciate the posting of the parameters. It's interesting information.

Still, all I want is for this engine to only go into V4 mode while on the freeway. I agree with an earlier poster about not having it kick in until above about 45-50MPH. The engine lugging is just annoying. It's especially bad if you do not feather the throttle. if you jump on it a bit while going slowly in V4, you get whacked as it goes into V8, and then again when it downshifts. That's just really bad programming. GMC really has some opportunity here, because my 6 speed Acadia shifts in a dumb way as well--completely misses the power band in 3rd gear. Do the GM programmers drive these vehicles in the real world, or is this purely a mileage play?

Sorry for the attitude. I had a long stop and go commute this morning, and this was noticeable and annoying, so it's fresh in my mind.

Well, the bottom line is you can pretty much control AFM however you want but you need a programmer or a tune to do it and of course the risks of all the warranty hoopla that people worry about. The safest and lowest risk way that i can think of for you guys worried about warranty is buy a new pcm (pretty cheap if you buy used) and make that the one you tune. Swap in the stocker if ever needed.

Disabling the AFM on my truck thru the Diablo tuner was worth every penny. Its like two different trucks now. Not noticeable MPG drop and instant response driving. GM should have a option to control AFM. It would never get used,,