Cylinder deactivation for the 2021-2023's?

[301Bobbo]

If you have tow/haul I don't think it'll deactivate cyls in that mode. But that's hardly a fix.

 

[nick14226]

If you have tow/haul I don't think it'll deactivate cyls in that mode. But that's hardly a fix.

L9 is the only way to shut off DFM at the moment, no other driving modes will do it.

 

[nick14226]

They said it's not. GM rewrote the code for 21+. It was open source before, but now they wrote the code internally.

Range is working on breaking the code to make a model for 21+, but they don't have anything now.

They expect an update by end of year.

There’s a guy on the 21-up Tahoe Facebook page that claims the previous gen Range has disabled the DFM on his ‘23 Tahoe. I pressed for more info and confirmation and he went silent. I’m not buying one to experiment, and would have to imagine Range tried it or knows it won’t work, but if anyone has an RA003 laying around and wants to give it a try, please do!

 

[Deuce16GMCs]

There’s a guy on the 21-up Tahoe Facebook page that claims the previous gen Range has disabled the DFM on his ‘23 Tahoe. I pressed for more info and confirmation and he went silent. I’m not buying one to experiment, and would have to imagine Range tried it or knows it won’t work, but if anyone has an RA003 laying around and wants to give it a try, please do!

This would be great.

 

[SSGUNNER]

I’ve gotten used to mine and the DFM even with my Borla S Type muffler. Don’t want it kicking in I’ll just feed it more gas. I’m at 24,300 on the clock and loving it. At this point I’ve lost hope and just accepted DFM lol.

 

[Deuce16GMCs]

I’ve gotten used to mine and the DFM even with my Borla S Type muffler. Don’t want it kicking in I’ll just feed it more gas. I’m at 24,300 on the clock and loving it. At this point I’ve lost hope and just accepted DFM lol.

Thanks for chiming in. Does the borla or the aftermarket exhaust the GM sells for the 6.2 cancel out a lot of the squealing?

I may upgrade the exhaust.

 

[nick14226]

Thanks for chiming in. Does the borla or the aftermarket exhaust the GM sells for the 6.2 cancel out a lot of the squealing?

I may upgrade the exhaust.

You can simulate it, clamp your flaps open temporarily and see if the noises go away. You might get the “helicopter” sound but if the squealing goes away that’s driving you nuts you can upgrade to a corsa that’ll “fix” it (no flaps, no drone, no dfm helicopter).

 

[SCiesie154]

What are these "flaps" you speak of?

 

[nick14226]

What are these "flaps" you speak of?

GM has them in the exhaust pipes, near the muffler, on the AFM and DFM 5.3 and 6.2. Spring loaded flap opens based on how many cylinders are firing (how much exhaust is flowing). 1 cylinder cruising and the flap is barely open, 8 cylinder wide open and it’s full open. The flap prevents strange exhaust notes when cylinders drop with the stock exhaust. They’ve been known to make noise and also resist full flow when full open.

 

[Deuce16GMCs]

GM has them in the exhaust pipes, near the muffler, on the AFM and DFM 5.3 and 6.2. Spring loaded flap opens based on how many cylinders are firing (how much exhaust is flowing). 1 cylinder cruising and the flap is barely open, 8 cylinder wide open and it’s full open. The flap prevents strange exhaust notes when cylinders drop with the stock exhaust. They’ve been known to make noise and also resist full flow when full open.

View attachment 396692

I would say the squeal while cruising, even when L9 (DFM deactivation) is engaged, being caused by the flap.

The TSB does openly state that the squeal that's present when coming to a stop and accelerating from a steady cruise at 60-75 mph is being caused by the retarding of the spark when deactivated cylinders reactivate. Which is why that noise goes away when L9 is engaged.

Honestly, the worst squeal is the one from coming to stops. It embarrassing to hear the car squeal at all 6 stop signs in my neighborhood. Neighbors are looking at me like I'm driving a $90k piece of junk.

 

[nick14226]

I would say the squeal while cruising, even when L9 (DFM deactivation) is engaged, being caused by the flap.

The TSB does openly state that the squeal that's present when coming to a stop and accelerating from a steady cruise at 60-75 mph is being caused by the retarding of the spark when deactivated cylinders reactivate. Which is why that noise goes away when L9 is engaged.

Honestly, the worst squeal is the one from coming to stops. It embarrassing to hear the car squeal at all 6 stop signs in my neighborhood. Neighbors are looking at me like I'm driving a $90k piece of junk.

With the corsa I can really hear what’s happening with DFM. When coming to a stop the cylinders drop as you’re coasting/braking, and then just before you’re totally stopped the cylinders (and exhaust) come back to life. Some notice a bit of a lurch when that happens, and guessing it’s when the squeal happens you’re describing in the neighborhood. Clamping open the flap is a grasp at straws approach, but seems you’re getting to that point. No guarantee it would help.

Point being, if opening the flaps doesn’t help I doubt an aftermarket muffler or exhaust will either.

 

[Deuce16GMCs]

With the corsa I can really hear what’s happening with DFM. When coming to a stop the cylinders drop as you’re coasting/braking, and then just before you’re totally stopped the cylinders (and exhaust) come back to life. Some notice a bit of a lurch when that happens, and guessing it’s when the squeal happens you’re describing in the neighborhood. Clamping open the flap is a grasp at straws approach, but seems you’re getting to that point. No guarantee it would help.

Point being, if opening the flaps doesn’t help I doubt an aftermarket muffler or exhaust will either.

You hit the nail on the head with the cylinders reactivating once you drop below 14 mph. That's exactly when the squeak happens. Depending on how many cylinders are reactivating determines whether it's a tiny squeal or long drawn out squeal.

Were you hearing the squealing before the Corsa?

 

[nick14226]

You hit the nail on the head with the cylinders reactivating once you drop below 14 mph. That's exactly when the squeak happens. Depending on how many cylinders are reactivating determines whether it's a tiny squeal or long drawn out squeal.

Were you hearing the squealing before the Corsa?

Negative, with the 5.3 I only noticed the lurch occasionally and now can hear it with the corsa but don’t feel it. For me cruising around 35 - 40 mph is when DFM has driven me nuts, I get a vibration that goes away with L9. There’s a really noticeable stretch I’m about to drive on for the first time with the corsa today and hope it helps. I’ve noticed it less with the exhaust so far and also running higher octane.

 

[SCiesie154]

Thank you Nick, for your most excellent explanations!

 

[SSGUNNER]

Thanks for chiming in. Does the borla or the aftermarket exhaust the GM sells for the 6.2 cancel out a lot of the squealing?

I may upgrade the exhaust.

With my set up there is no squealing but there is the helicopter sound when it kicks in.

 

[Eusibius2]

I'm beginning to think I'm ignorant or naive. I've got a 2022 6.2L and have never noticed any change in performance while driving around town or cruising at 65mph. All seems the same to me. 11k miles on the clock.

I haven't made any changes yet though. Stock exhaust, air filter, etc... I've flipped from D to L9 on occasion to see if I can tell a difference, but seems exactly the same.

 

[Deuce16GMCs]

I'm beginning to think I'm ignorant or naive. I've got a 2022 6.2L and have never noticed any change in performance while driving around town or cruising at 65mph. All seems the same to me. 11k miles on the clock.

I haven't made any changes yet though. Stock exhaust, air filter, etc... I've flipped from D to L9 on occasion to see if I can tell a difference, but seems exactly the same.

Any squealing/chirping sound when coming to stop from 25-30 mph. You'll hear it as the speedometer crosses down at 14 mph. Keep drivers windows down only, other windows up.

 

[Eusibius2]

I've have my windows down almost every chance I get. Never heard any squealing. Winter months they're up though. Weather was unusually nice last week, and windows were down.

 

[WalleyeMikeIII]

Any squealing/chirping sound when coming to stop from 25-30 mph. You'll hear it as the speedometer crosses down at 14 mph. Keep drivers windows down only, other windows up.

None. My has a bit of a "belt squeek" sound at cold start, for 30 or so seconds. Pretty sure this is the timing retard and rich running for catalyst light off...other than that, just sounds like a GDI V8.

 

[nedac]

My 2021 Suburban was built in August 2021 and cylinder was deleted at the factory.

According To the dealer that just replaced my POS fuel pump control module after it left me on the road, the cylinder deactivation is the primary cause of lifter failure.