DFM disabler released

[nick14226]

@nick14226, thanks for that explanation. Makes total sense. As I recall, the Z71 available w/ the 5.3 or 6.2 in 2022 as well, correct? Guessing the 6.2 has a bit more gusto w/ cylinders deactivated than the 5.3, so that could also be a difference; you haven't said which engine you have. For sure exhaust mods would make the changes more noticable....bummer it is so obnoxious for you. Glad you have a solution you can live with though.

Sorry, yes 2022 z71 5.3
The corsa had no impact on the drivability. It’s well designed and eliminates the flapper, but no drone from DFM. Just can hear the cylinders kick back during decel at 14 mph, which again doesn’t bother me. I’ve 6.2 owners with the same complaints as the TSB defines that I experienced, so again, think you’re lucky

 

[djnice]

Related to gas mileage. Before I get the disabled, I've been experimenting L9 VS D with the 5.3 in my AT4 that's lifted. I'm not seeing any difference on various drives. The other day I got 24 mpg in L9 with a mix of city and highway average speed in the 60's. It all depends on the road you're on and how much incline and wind there is. So really hard to evaluate the impact. My life average is in 14's, but that is lots of stop and go. Also, I think the front end aero on the AT4 and Z71 has -2 mpg impact compared to suburbans that I've rented.

 

[Marky Dissod]

Please note: I don't own one of these direct injection engines with the 'How Many Cylinders Now?' bug/feature.
That said ...
There are two situations during which I see MINIMAL harm in this feature being active:
1. 0% throttle decelerations (aka Decel Fuel Cut Off / DFCO)
2. Whenever the engine coolant temp has exceeded somewhere between 221F / 105C & 230F / 110C
(I'm using that coolant temp threshold as a proxy for being in danger of overheating)

1. While you happen to be decelerating @ 0% TPS, you don't need ANY cylinders,
the road is effectively turning the wheels, which are turning the axles, which are turning the transmission, which is turning the engine,
because no cylinders are receiving ANY fuel anyway - so it's kind of a moot point.

2. It should be a well-known fact that Chrysler's earliest attempts at Engine Half@$$ allowed the 4 lazy cylinders to get so cold,
they cracked engine blocks.
IFF the engine is in danger of overheating, running on the minimum number of cylinders needed and varying them moment-to-moment
may help to keep engine temps down in all 8 cylinder sleeves, or at least delay overheating by a minute or two, which may be very helpful

Under the vast majority of normal driving circumstances, however,
there is NO REASON to have Cylinder Confusion enabled *except possibly for the two caveats above*.

This gentleman brings up a good point regarding the lack of oil flow to the DFM lifters after running this product long term. Link to video:

Actually he does NOT.
The way On/Off lifters work, is when the cylinder goes lazy / Off, oil flow is DENIED to that cylinder's lifters.
So when the engine is in V8 mode, oil is pumping those lifters up, same as it's worked since hydraulic lifters first showed up.

On / Off lifters will last longest if they are always ON / if Cylinder Confusion is disabled.

 

[BacDoc]

Hi @nick14226, can you elaborate on what ruins your drive on a daily basis. I guess each one these vehicles are different, but in my Denali (which is so whisper quiet in the cabin I cannot even hear the stock exhaust, and really cannot even hear the engine unless its above about 3500 RPM) the ins/outs of DFM are completely unnoticeable. Even with the windows down, the wind noise easily drowns out any drivetrain sounds. (I Must be one of the lucky ones, or maybe on this trim level, it is less perceptible). Also, after disabling, do you notice any fuel economy differences? I routinely get 21+ MPG on flat highways if I keep her under about 73MPH, did 400 Mile round trip last weekend and got 22.1 on the way there, and 21.4 on the way home.

Anyway, I am not saying you are wrong, just more curious on what characteristics of the DFM in your vehicle make your driving experience poor. In my rig, I set the cruise and life is grand, if I need power, I hit the gas, and there is immediate downshift and the 6.2 comes to life and I am off to the races. In town, I never notice it engaging or disengaging...I'm at 30.5k on the odometer, and things are still smooth as silk. That said, my rig is 100% stock on everything engine/exhaust related.

EDIT: I just re-read the whole thread, see your complaint is primarily shudder/vibration at cruise or gentle throttle application (presumably not enough power demand to reactivate all cylinders?)
Is it possible you actually have the transmission shudder issue, and it is just more noticable when DFM is enabled, vs DFM? Do you have the 5.3 or 6.2? That coule be another factor, as could be your performance exhaust?
All good, seems disabling it helped your application...glad there is a solution that works for you.

Mike - this is exactly what I would say about my 2024 Chevy Tahoe 6.2l. Except I am only around 6k on odometer. After reading a lot of posts here I really started listening with radio off and windows down. I never hear anything related to DFM or feel any shutter or anything different in the ride.

It’s got me frustrated as I was considering getting exhaust upgraded as the engine is way too quiet unless I am back but the tailpipes. The 6.2l sounds beautiful but way too quiet. I am afraid of changing exhaust and hearing or feeling the DFM!