DFM disabler released

WalleyeMikeIII said:

@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.

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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

Related to gas mileage. Before I get the disabler, 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.

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*.

Thiccboii said:

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:

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Actually he does NOT.

NOTE: THE FOLLOWING IS *WRONG.
PLEASE CAREFULLY READ THE CORRECTION IN POST #75 BY @RG23RST.
*(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 started replacing solid lifters.)*

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

WalleyeMikeIII said:

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.

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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!

Marky Dissod said:

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*.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 started replacing solid lifters.

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

Click to expand...

Please don't post misinformation. The lifters are de-activated via oil pressure directed from the oil control solenoids. Oil pressure is not reduced to the hydraulic lash adjusting portion of the lifter during this operation. In reality the lifters see more lubricating oil during DFM operation. In normal use the solenoids will pulse oil through these passages to keep them clean and eliminate any air pockets that could impact switching time. I'm not sure if the Range device allows this to still occur so there could be some concern with the small passages getting clogged but I don't think its much issue as long as your change your oil.

BacDoc said:

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!

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You're more likely to hear and feel vibrations from the DFM once you get more miles on the rig. 10-20 thousand miles and the springs on the exhaust valve (or valves if you have a 6.2) get a little weaker and the valves can flutter meaning more unwanted vibrations working their way into the cab.

I have a 2021 Yukon with 6.2L and 55K miles - bought used 1 year ago.

It idles with a pleasing purr/rumble and haven't noticed any noises/vibrations/power-issues while driving except...

When coming to a full stop, the engine seems to sputter a bit (like it' needs a tune-up / going to die) and then it revs up just a bit to idle smoothly. Not sure if this is DFM or auto-stop feature related. I have the auto-stop = off via that after market unit I installed.

tagexpcom said:

I have a 2021 Yukon with 6.2L and 55K miles - bought used 1 year ago.

It idles with a pleasing purr/rumble and haven't noticed any noises/vibrations/power-issues while driving except...

When coming to a full stop, the engine seems to sputter a bit (like it' needs a tune-up / going to die) and then it revs up just a bit to idle smoothly. Not sure if this is DFM or auto-stop feature related. I have the auto-stop = off via that after market unit I installed.

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It’s adjusting timing (torque management) to protect the transmission. Does it remotely effect driving the vehicle or just a nuance you notice?

iamlegion said:

It’s adjusting timing (torque management) to protect the transmission. Does it remotely effect driving the vehicle or just a nuance you notice?

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Just a nuance as it only occurs immediately after a full (hard) stop for 1-2sec till smooth idle. Would have to stop, and then immediately punch it within 1sec to see if it had any affect on mobility and haven't tried that.

I have a 21 Suburban with a 6.2 and 76,000 miles, I hardly notice any noise and everything operates seemlessly. I am only interested in eliminating DFM because I plan to keep this vehicle for a very long time. I have only had it for 4 months now but I love it. I would like to make the sound a little louder but I don't want to get in that drone range while towing our travel trailer. Years ago I had a giant Walker Dynomax muffler, single 3" in and 3" out and over 30" long, that was a little louder but not noisy. I might try one of those again.