Cylinder Deactivation Issues?

Donstar · February 19, 2017

Donstar..................do you work for or get paid a stipend from GM????

No, but I sure like my truck and I get treated well by my local dealerships!! I had some major issues with my previous truck ('09 Sierra) and I found GM customer support reasonable when repairs were beyond the scope of the dealership. Prior to this I had a '00 Silverado for nine problem free years.

Hoginedgewood · February 20, 2017

I happen to agree with you on that. When I tune my current truck I'm going to ask if this is possible. So that at cruise on the highway you can drop down to v4 but on all street driving you'll stay on v8

This never acured to me until I read it on another forum a month or so back

Sent from my Nexus 6P using Tapatalk

thats what I've been attempting, I put the trans in M5, then when I get above 55 mph I go D or 6. Seems to be what you're after.

PatMac · May 20, 2017

Does anyone know if Hypertech is planning to release a tuner for the 2017 models? Several emails to tech support have gone unanswered. If not Hypertech, can anyone recommend the best alternative tuner? Diablo seems to be the only solution... I guess.

Thanks

Thomcat · May 21, 2017

Had them in my '07, '12 and '13 Avalanches and in the '16 Silverado. AFM 5.3l manufactured after 1/11 should not have any oil burning related problems.....they contain all the engine mods made to correct the problem, i.e. updated valve cover relocating PCV valve takeoff to reduce oil suction , AFM oil discharge valve baffle in the crankcase to prevent splash on the deactivated AFM cylinders and redesigned AFM valve lifters. Main reason I dumped the '07......no problems with any of the modified 5.3ls

4-8 transition is another matter - I don't really notice it in the driving I do and didn't want to permanently disable through tuning because I have no idea what affect it will have if one or more of the 4 AFM cylinders' collapsible lifters remain locked long term.

Edited May 22, 2017 by Thomcat

Spendit · July 21, 2017

New to me 2014 - 1st AFM system (and I do notice the V4-V8 shift). My question to those in the know - do they cut out the same cylinders (which ones) and is it done via: spark and fuel, ect.... trying to get my head around this and parts durability. Will certain cylinders wear sooner, plugs carbon up sooner, ect....

Grumpy Bear · July 21, 2017

Quote of post #14.

I'm going to add a little tidbit in here as well.

I had a 2007 Tahoe LTZ that suddenly went into limp mode and threw codes. Traction Control and Stabilitrak lights came on. I had a misfire on cylinder 1, because the intake valve was not opening.

I brought it in and they found the issue to be caused by the AFM. They said that it wore out the rockers and wore a lobe off the camshaft. They also told me this was a common problem due to the fact that you're essentially "dragging" along four cylinders when the motor goes into 4 cylinder mode.

That sir is a lubrication issue and not an AFM issue. Your pistons get drug up and down a cylinder at a rate of about 20 feet per second on the highway. Stop that from happening with some tuner.

Ever notice how it takes a non-second to come to a wrong conclusion or accept a false premise and a lifetime to get rid of them?

Edited July 21, 2017 by Grumpy Bear

Pearl2017 · July 22, 2017

Whatever side you come down on AFM the intent of the design is clear. Its intent is to gain a tiny fraction of a MPG to meet Mileage regs and that's it. The added Cost we are paying for and complexity to the machine adds points of failure. If it weren't for regs would anyone think for a second the gimmick of AFM would even be in there? Disable it and enjoy!

Grumpy Bear · July 22, 2017

Whatever side you come down on AFM the intent of the design is clear. Its intent is to gain a tiny fraction of a MPG to meet Mileage regs and that's it. The added Cost we are paying for and complexity to the machine adds points of failure. If it weren't for regs would anyone think for a second the gimmick of AFM would even be in there? Disable it and enjoy!

A graphic posted to my build thread. Note the 50 mph marker. Tow 5 and M5. Yellow and gray. The difference is the AFM is active during the tow mode and disabled in manual.

The mileage difference in this test was 6.5%. Is that significant or a 'tiny fraction'?

The amount of difference it makes doesn't hinge on it's design. It hinges on its use and that friends is controlled by your right foot. Just sayin.

Nanotech Environmental · July 22, 2017

The '17 I bought in June is my 1st vehicle with AFM. I must say that so far I quite like it. I certainly does help improve fuel mileage substantially. It also seems to work pretty seamlessly. I've checked my oil a number of times since new and it doesn't appear to be using any in ~4000 miles (6000 km) so far.

In many ways you get the best of both worlds; fuel mileage and V8 power.

That being said, there is some mis-info and outright nonsense on this thread;

(Paraphrase previous posters in " ")

"AFM doesn't affect mileage" - That's complete BS. In situations that call for AFM, the fuel economy will improve from 10-30% over what it would be if it stayed in V8.

"AFM is a gimmick and the intent is to only give a tiny fraction of a MPG improvement & add complexity" - Sorry, not true at all. AFM, when used properly and as designed will give average fuel economy improvements of several MPG on both city and highway. Many people see improvements of 4-7 mpg or more over 2006 and earlier era trucks. That's nothing to sneeze at. My own results have been quite impressive to me & more than I expected when I bought the truck. Want complexity? Buy an Egoboost

"My AFM didn't work properly and always surged" - There are 2 possible problems here; Driver error, or a complete failure, or unwillingness to get the problem remedied under warranty. The truck or it's design is not to blame for either of those things.

Edited July 22, 2017 by 3beejay3

KARNUT · July 22, 2017

In my 14 GMC on my frequent trips to myrtal beach from Texas (1200 miles ) each way I didn't even gain 1 mpg with the V4 on. I had a hand held tune (hyper tec). Cruise was set at 72 MPH. What's really funny and always happens even with different vehicles I get better mileage going west than east, always with cruise on at 72.

Thomcat · July 22, 2017

New to me 2014 - 1st AFM system (and I do notice the V4-V8 shift). My question to those in the know - do they cut out the same cylinders (which ones) and is it done via: spark and fuel, ect.... trying to get my head around this and parts durability. Will certain cylinders wear sooner, plugs carbon up sooner, ect....

Same four cylinders dedicated to cylinder deactivation. Basically, AFM cylinders have collapsible lifters, deactivation is done by diverting the oil supply to these lifters (closing the intake/exhaust valves) to a discharge nozzle in the sump. This was the main cause of oil burning in the engines mfrd. prior to 1/2011 a corrective baffle was installed to direct excessive oil discharge off the lower cylinder walls of the "dead" AFM cylinders which would lead to clogging of the lower oil control rings set on the pistons of these cylinders. In AFM operation the valves are inoperative so no fuel is introduced but the spark remains active. On a 4/8 V8 two cylinders per bank are AFM cylinders so the engine remains balanced - same with the 4/6 V6 only two are AFM cylinders. Unlike that POS Honda 3/4/6 V6 engine in my '15 Pilot the GM engines are never inherently unbalanced in AFM mode and does not have to rely on Honda's $600+ ea. active motor mounts which get beat to hell to compensate for the horrible harmonics of unbalanced V3 operation.

Since the AFM cylinders while deactivated retain normal splash lubrication and the plugs continue to fire there should be no additional wear on cylinders or build up of carbon on the plugs. Maintained properly there should be no change in reliability or durability of AFM engines compared to non AFM engines. Some people fault driveability, but transition is almost flawless and I'm no longer cognizant of the changes

Thomcat · July 22, 2017

Edited July 22, 2017 by Thomcat

duquephart · July 22, 2017

In my experience ('17 5.3) the transition back and forth is undetectable, unless you are watching the display you wouldn't know. But, it's that back and forth that bothers me. I think it transitions too often and at too low a speed. Steady, flat highway driving is one thing. The least bit hilly and it's all over the place, not to mention 40 MPH in town. The solution is to use L5 and live with the mileage hit.

Nanotech Environmental · July 22, 2017

In my 14 GMC on my frequent trips to myrtal beach from Texas (1200 miles ) each way I didn't even gain 1 mpg with the V4 on. I had a hand held tune (hyper tec). Cruise was set at 72 MPH. What's really funny and always happens even with different vehicles I get better mileage going west than east, always with cruise on at 72.

Are you saying that your fuel use didn't go down, according to the DIC during the periods that V4 was activated?

KARNUT · July 22, 2017

Are you saying that your fuel use didn't go down, according to the DIC during the periods that V4 was activated?

Thats right, the only time it was In V4 mode for any length was down hill when your coasting. At 72 MPH it wasn't on much, just enough to mess up the good exhaust sound.