DFM disabler released

[jfoj]

Update on the Range module, finally had a chance to get a more advanced scan tool on the truck today. During Decel with Fuel Cut Off (DFCO) the ECU did show cylinder deactivation. I could watch the incremental counters for each cylinder increase during DFCO and the instantaneous Fuel Economy at 99 MPG.

While I might prefer the DFM be 100% disabled all the time, having it only active during DFCO is better than nothing. Overall if seems that is clearly exercises the lifters far less than if the DFM was always active. Additionally some activity to flush and exercise the lifters may not be a bad thing??

Anyway, I have to next test and monitor with the transmission in 9th gear to see what happens during DFCO. I would not likely drive at full highway speeds with the transmission in 9th gear for many reasons.

The one thing that is annoying about the Range device is it will not allow all the OBDII Readiness Monitors to set, this may be the way they disable the DFM? So this means the Range device will need to be removed prior to any state Emission Inspections to allow all the Emission Readiness Monitors to be set, then it would need to be reinstalled again.

Just a bit more effort, but overall this still seems worth it in the long run.

 

[Marky Dissod]

I have to next test and monitor with the transmission in 9th gear to see what happens during DFCO.
I would not likely drive at full highway speeds with the transmission in 9th gear for many reasons.

FYI, 10L80's 9th gear is basically 4L60's 4th gear.
When the engine load in 10th gear gets too high, it would just downshift to 9th / 4L60E's 4th.

I can only think of 1 reason to avoid 10th altogether:
if an overrun clutch is applied in 9th. Otherwise it should be all good.

 

[Scarey]

Very cool. I think that is what allot of us suspected. I agree you may want oil occasionally to cycle through the lifters. Not getting cooked and gumming up. Would be very interested in seeing what your L9 dfco results are. Thanks for putting the effort in.

Ps. I’m curious if there is various stages of dfco. In steady state cruise and lightly letting off the gas, maybe throttle closes and fuel starvation. Vs rapidly letting of the gas and going into full cylinder deactivation to gain the additional engine deceleration?

PSs last thought. I wonder if there could be any connection with the bearing failures on the 6.2s, maybe low engine oil pressure caused by dfco?

 

[RG23RST]

You need to watch the actual current to the solenoids, not what the ECM is commanding. Remember the Range device sits on the “output” side of the ECM. With the Infineon SOC they use it’s pretty obvious what’s happening.

 

[RG23RST]

Very cool. I think that is what allot of us suspected. I agree you may want oil occasionally to cycle through the lifters. Not getting cooked and gumming up. Would be very interested in seeing what your L9 dfco results are. Thanks for putting the effort in.

Ps. I’m curious if there is various stages of dfco. In steady state cruise and lightly letting off the gas, maybe throttle closes and fuel starvation. Vs rapidly letting of the gas and going into full cylinder deactivation to gain the additional engine deceleration?

PSs last thought. I wonder if there could be any connection with the bearing failures on the 6.2s, maybe low engine oil pressure caused by dfco?

The answer to all your guesses is no. GM has used an advanced neural network/AI algorithm in the engine controller since this generation debuted in 2018. What this allows is very low latency calculations to occur based on sensor data to efficiently determine the best firing fraction, fuel trim, ignition timing, throttle valve position, charging state, commanded oil pressure and so on. Its partly why tuning them is a nightmare that involves re-training this neural network.

The 6.2 bearing issues are a supplier quality concern is my understanding. They don’t have “low” oil pressure unless the pump is malfunctioning somehow. Engineers figured out a long time ago volume, not necessarily pressure, is best. It’s the film strength of the oil keeping metal parts from French kissing, not the PSI of the oiling circuit forcing them apart.