Surprise results after disabling DFM on my AT4X 6.2

goatspeed

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I roll a 2023 AT4x half ton and I recently decided to disable the autostop by way of a Carbyte. This little device sticks on your diag port just north of your hood lever in the cab. It also disables DFM/AFM which wasn't really a selling point for it for me...I just wanted the autostop stopped without pushing the button every time I drove. So a week now into having DFM disabled I have some impressions of being in full v8 mode all the time and I wonder if anyone else here has gone through this. This isn't really an AT4X specific thing obviously. But here we are.

So first impression is that we must be in v6 mode ALOT. Without knowing exactly when cylinders are shut off prior to installing Carbyte, I would have assumed were are always in v8 mode, and then if we get on the highway and set our cruise etc, it might toggle down to v6 and v4 mode if possible. In fact, v8 all the time makes my truck a completely different animal. Accelleration at any speed is faster. I should really do a 0-60 from dead stop with DFM enabled and then disabled for better science, maybe I will when I can get at some non slippery roads (Minnesota winter). I've had to adjust how I step on the gas at a stop light because I've nearly lunged into the car ahead of me a couple of times now. Without any good science, my impression is that I was running in v6 mode almost all the time. And the at4x is now a sports car.

On the topic of mileage, obviously there is a massive swing there. In pure city driving, I barely get above 10mpg. Mixed driving gets me to around 14mpg. And on a long trip where I was able to use the cruise at a modest 65mph, I was at 15.7mpg. Before, those numbers were 12/14/18 mpg respectively. For reference, I have no lift/leveling other than factory. I do have 295/65/r18's on it which is roughly the same height as factory, but 2 cm wider.

Now I really don't care about mileage. When I get a truck, I lift it, put big tires on it, add a grille guard etc...and immediately give up 2-3mpg for the sake of awesomeness. It just so happens this time around I didn't need to do anything to my new truck because it's an AT4x. But it would seem that without DFM/AFM, the 6.2 is almost unusable for most because we go back to 1990's fuel mileage. But I can't stess enough...my truck is now a completely different animal. Anyone else disable DFM and have similar observations?
 

Fun fact: the DFM system in the 2019+ trucks allows the engine to run using as few as 2 cylinders! Previous generations with AFM would switch between V8 and V4. I don't think I'm the only one who thinks AFM/DFM is the Achilles heel of the GM V8's so I have the Carbyte device installed as well. It may not remove the components from the engine that are prone to failure, but I would like to think disabling the cylinder deactivation prolongs the life of the engine. Opinions aside, what you said is spot on - little bit of a hit in fuel mileage but I do like the better throttle response and having the V8 sound like a V8 all the time. I've also never been a fan of the auto start/stop. As @gemarsh said - you didn't buy a large displacement V8 truck for fuel economy!
 

2024 Yukon XL AT4 6.2L with Carbyte here... The truck is entirely stock with original wheels/tires.
It really is a different animal with the Carbyte. I purchased the Carbyte to disable the AFM/DFM and the annoying start/stop feature, but the truck really does feel and drive more sporty with it installed.
We drove from North Texas to North Florida and back over the holidays and it was fully loaded with luggage and people. We averaged 19 mpg on the way out, and just over 18 on the way back. (into the wind) To be fair, that is a pretty flat drive, but I have driven all kinds of trucks and large SUVs in the last 30 years that faired much worse in terms of mpg. My city driving fluctuates between 10-14 mpg. I don't think having the Carbyte installed has made the mpg any better or worse.
 

Idk how many miles you’ve put on it since the switch but the transmission and you will change driving habits. Once it relearns the mpg should come back to near before. Its said to take a few thousand miles for pressures and shift points to acclimate.

The afm is a joke bc the transmission will need to run at lower gears and maintain higher rpm’s for the same conditions. When the full power will easier pull the vehicle through its everyday varied conditions.
 

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With the Carbyte, does the DFM still come on when coasting like the Range claims it will do with their device? Meaning, neither device truly shuts off DFM all the time? Or am I wrong? Thanks.
 

Amazing what getting rid of emissions crap does on those V8s and Diesels for performance and reliability. I'm contemplating purchasing a preemmisons diesel or just deleting a new one immediately. Trust it better being deleted. Fuck the EPA. There I feel better now. 🤣
 

With the Carbyte, does the DFM still come on when coasting like the Range claims it will do with their device? Meaning, neither device truly shuts off DFM all the time? Or am I wrong? Thanks.
No the Carbyte doesn’t do the coasting shutdown. I’m not sure if that’s actually dfm engaging or something different. Either way Carbyte doesn’t do that. But the drawback is that the engine has much less engine braking so depending on where you live you can decide how you feel about that.
 

With the Carbyte, does the DFM still come on when coasting like the Range claims it will do with their device? Meaning, neither device truly shuts off DFM all the time? Or am I wrong? Thanks.
I had the Range device before and swapped it for the Carbyte. You do not get the coasting garbage with the Carbyte...which is great. With Carbyte, the DFM is disabled once you get over 40mph. If you never get over 40, then it doesn't have a chance to grab onto the DFM to disable it.
 

Amazing what getting rid of emissions crap does on those V8s and Diesels for performance and reliability. I'm contemplating purchasing a preemmisons diesel or just deleting a new one immediately. Trust it better being deleted. Fuck the EPA. There I feel better now. 🤣
agreed - my deleted LML was a beast with power and Mileage
 

Glad I saw this a couple days ago, ending putting one on my '25 I picked up last weekend and now it drives like I expected it to.
 

Just got the Carbyte going and for those that have updated the unit did you just go with the latest update version or did you download them in order???
 

Just got the Carbyte going and for those that have updated the unit did you just go with the latest update version or did you download them in order???
I received Carbyte and installed it on December 10, and an update had just come out. I installed that update, but I did not see any others beside that one. There may have been another update since then but I am not aware of it.
 

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