DFM disabler released

[Antonm]

How did this ridiculous rumor get started? Read GMs own service description of DFM operation that was posted earlier in this thread. DFM is NOT active during deceleration fuel-cutoff mode aka what you experience when coasting down with quiet exhaust. The engine re-fires at 14mph slowing down if you continue to coast.

DFM IS NOT ACTIVE DURING DFCO. Not sure what else to say. The solenoids aren’t energized and the lifters aren’t being de-activated. DFCO is normal operation whether the engine has DFM or not. My company 2500 with the L8T does the exact same thing. If you want to remove this behavior you need a full tune.

Put the truck in L9 (which actually disables DFM) and that doesn't happen. Cutting off fueling while coasting is not new (even my mechanical P-Pump Cummins engines from the 90's do that). Part of the current DFCO is to allow the lifters (all of them) to collapse which is thing we all just want disabled and are not getting.
So sure, one could argue the semantics that DFCO its separate from and not directly part DFM, buts its a stretch as it does request DFM to activate and collapse the lifters (which is the main thing we all wanted to stop from ever happening). If DFM were "disabled" then when DFCO requested it, it wouldn't do it, so DFM is not disabled.

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[Scarey]

I agree, range is an improvement to the stock system. Their web site is misleading though. Is carbytes response just simplifying, maybe? I think I understand your question and it’s a good one. I would like to know for fact in coast are the cylinders just starved of fuel or are they also using cylinder deactivation through collapse able lifters. I’m guessing they are deactiteing the cylinders with the collapsable lifters because it makes sense the way the car decelerates, almost brakes when you take your foot off the gas. And it makes sense in another thread I read you don’t want to keep moving air through the cylinder because you’re going to increase the cooling. By deactivating the cylinder you are you keeping it warmer, not moving air? Don’t know for sure but I would like to know for sure.

 

[Scarey]

Just read Antony response. I agree, we are all trying to find the same answer which will help us each make our on decision on hw we want to deal with this crappy lifter thing. Maybe carbyte and range want to chime in here? You know they are lurking.

 

[RG23RST]

Weather is called Dfm or dfco, doesn’t matter, when you take your foot off the gas all the lifters collapse keeping the valves closed. In steady state cruise the system collapses some lifters to take some cylinders off line. This whole discussion is about lifter collapse. We all want a normal lifters and no lifter failure because of a designed collapsible lifter. We just want a normal fire breathing v8 all the time.

Here’s a quote from carbyte people on the at4 forum.

The 0-cylinder mode activates DFM (valves are not moving) and shuts off the fuel. Carbyte prevents both from happening once the 40mph condition is met (as explained in our previous post), with the only downside of using negligibly more fuel.

NO! Stop with the misinformation. Some of you are wittingly or unwittingly getting caught up in marketing between two competing business. See below directly from GM. DFM is NOT active during deceleration fuel cutoff. Deceleration fuel cutoff is on any time you are coasting outside of some vehicle warmup logic in the ECM. NO LIFTERS ARE DEACTIVATED DURING THIS MODE. NONE.

 

[RG23RST]

Put the truck in L9 (which actually disables DFM) and that doesn't happen. Cutting off fueling while coasting is not new (even my mechanical P-Pump Cummins engines from the 90's do that). Part of the current DFCO is to allow the lifters (all of them) to collapse which is thing we all just want disabled and are not getting.
So sure, one could argue the semantics that DFCO its separate from and not directly part DFM, buts its a stretch as it does request DFM to activate and collapse the lifters (which is the main thing we all wanted to stop from ever happening). If DFM were "disabled" then when DFCO requested it, it wouldn't do it, so DFM is not disabled.

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L9 activates engine braking logic in the ECM/TCM and also inhibits DFM. DFM does not activate during DFCO in ANY ECU MODE. There are logic changes between coast/engine braking modes and that is what you are experiencing. I'm going to post this until y'all get it.

 

[RG23RST]

Just read Antony response. I agree, we are all trying to find the same answer which will help us each make our on decision on hw we want to deal with this crappy lifter thing. Maybe carbyte and range want to chime in here? You know they are lurking.

There is no answer to "find." GM clearly spells out the logic and operating modes of DFM. You're more than happy to see for yourself by using a scan tool and waiting for the DFM flag to light up during coast down. You'll burn every drop of oil in Saudi Arabia before that happens because the logic isn't in the ECU.

 

[Antonm]

NO LIFTERS ARE DEACTIVATED DURING THIS MODE. NONE.

You are WRONG.
Again, you're arguing semantics, the lifters collapse on deceleration because DFCO orders the DFM lifters to do so. If you want to say that's not part of DFM fine, but the lifters are 100% collapsing during the deceleration portion, even Range Tech has admitted this and said they left it on intentionally because when they tuned it out, it made the driving experience different.

You are the one spreading the misinformation here.
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[Marky Dissod]

'The conditions below MAY be reasons for inhibiting deactivation'
'Decel Fuel Cut Off is active'
As in, MAY, or may NOT.
Any English teacher or proofreader will understand that DFCO might allow cylinder deactivation,
or that some DFCO events might also coincide with some cylinder deactivations.

DFCO and cylinder deactivation are two separate different UNRELATED things.
However, they are NOT mutually exclusive.
(I.E.: I MAY achieve turgidity even when NOT distracted by the thought of Milana Vayntrub in a bikini.)

the lifters collapse on deceleration
because
DFCO orders the DFM lifters to do so.

Antonm, DFCO does not cause cylinder deactivation either.
Their occurrences can overlap without one causing the other, however.

Since Antonm is not going to win any money by RG23RST being wrong,
and RG23RST is not going to win any money by Antonm being wrong,
ultimately, Range has already admitted that they did NOT deactivate 0-cylinder mode,
RANGE IS WRONG, and Milana Vayntrub is gorgeous.

 

[Antonm]

'The conditions below MAY be reasons for inhibiting deactivation'
'Decel Fuel Cut Off is active'
As in, MAY, or may NOT.
Any English teacher or proofreader will understand that DFCO might allow cylinder deactivation,
or that some DFCO events might also coincide with some cylinder deactivations.

DFCO and cylinder deactivation are two separate different UNRELATED things.
However, they are NOT mutually exclusive.
(I.E.: I MAY achieve turgidity even when NOT distracted by the thought of Milana Vayntrub in a bikini.)

Antonm, DFCO does not cause cylinder deactivation either.
Their occurrences can overlap without one causing the other, however.

Since Antonm is not going to win any money by RG23RST being wrong,
and RG23RST is not going to win any money by Antonm being wrong,
ultimately, Range has already admitted that they did NOT deactivate 0-cylinder mode,
RANGE IS WRONG, and Milana Vayntrub is gorgeous.

If Range corrects this error (which the obviously have the ability to do) , I'll happy jump back on the Range Tech band-wagon.

And I've walked into a bunch of AT&T stores, not a single employee in any of then looked at all like Milana Vayntrub. So I guess they false advertise too.
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[Marky Dissod]

When GM makes a two mode lifter that reliably lasts 300,000 miles -
Oh, wait, GM wants to stop making vehicles that reliably last 200,000 miles ...