DFM disable

[ILSilverado]

A Great reference for why AFM and DFM is horrible for your transmission. The thread is over 1400 pages.

 

https://www.corvetteforum.com/forums/c7-general-discussion/3999067-a8-transmission-failure-tracking.html

Edited February 14, 2020 by ILSilverado

[Thomcat]

1 hour ago, ILSilverado said:

A Great reference for why AFM and DFM is horrible for your transmission. The thread is over 1400 pages.

 

https://www.corvetteforum.com/forums/c7-general-discussion/3999067-a8-transmission-failure-tracking.html

Who cares what effect it has in a Corvette, this is a T1 forum? You can't compare problems in one model line with a different drivetrain to another. Besides an AFM engine has no business being in a sports car, probably why they offer the L5 version of the 6.2l without AFM for serious racing. To reiterate not a single Corvette has ever been manufactured fitted with a DFM engine!

 

Took them 12 years to redesign the engine from AFM to DFM, eliminating the LOMA manifold, AFM discharge valve and baffled valve cover not requiring a catch can and redesigned collapsible lifters.........the four main items causing problems in AFMs. Now instead of screwing around with hardware kludges and plastic LOMA manifold to shut down the same 4 cylinders............much faster state of the art processors can now rotate cylinder patterns to theoretically save gas but more importantly even out operation and wear in the engine in including the piston rings, crank.

 

Later AFM are much improved but after 12 years GM developed a new design where each cylinder see the same duty cycle which is maximized for power. DFMs offered now in the upper line Silverados with Tahoe/Suburban/Yukon to follow

[blckblt]

1 hour ago, Thomcat said:

Who cares what effect it has in a Corvette, this is a T1 forum? You can't compare problems in one model line with a different drivetrain to another. Besides an AFM engine has no business being in a sports car, probably why they offer the L5 version of the 6.2l without AFM for serious racing. To reiterate not a single Corvette has ever been manufactured fitted with a DFM engine!

 

Took them 12 years to redesign the engine from AFM to DFM, eliminating the LOMA manifold, AFM discharge valve and baffled valve cover not requiring a catch can and redesigned collapsible lifters.........the four main items causing problems in AFMs. Now instead of screwing around with hardware kludges and plastic LOMA manifold to shut down the same 4 cylinders............much faster state of the art processors can now rotate cylinder patterns to theoretically save gas but more importantly even out operation and wear in the engine in including the piston rings, crank.

 

Later AFM are much improved but after 12 years GM developed a new design where each cylinder see the same duty cycle which is maximized for power. DFMs offered now in the upper line Silverados with Tahoe/Suburban/Yukon to follow

Thomcat--do you work for Chevy/GM.  Not asking to be a D.  Just wondering how you know all this?  

[DuRsT]

Just now, blckblt said:

Thomcat--do you work for Chevy/GM.  Not asking to be a D.  Just wondering how you know all this?  

I was thinking the same thing.  I've never seen anyone this passionate about DFM lol

[BamX31]

On 2/12/2020 at 5:20 PM, Thomcat said:

Why would I disable something that I can't even notice in operation anyway? Besides gizmo has to be temporarily removed for inspection or servicing restoring DFM function.

 

These engines no longer use an OLM like the previous AFM version, DFM uses block mounted oil control solenoids for each cylinder which are constantly cycling. Doesn't seem to be any long term studies on the effects of keeping the oil control solenoids or collapsible lifters static for a long period of time and then reactivating for inspection or service.........and I have no desire to be the guinea pig that finds out.

I notice it every time I drive the truck and hate it. I can hear and feel when the thing drops cylinders. While having dropped cylinders waiting the 3-5 seconds it takes to figure out what to do when I want to mash the peddle to take off or pass a car is just ridiculous. I will be having this option looped out of the program if Range does not come up with something soon. Like the auto stop/start function. It is a gimmick. I ran two tanks with and two tanks without making the same exact trips and there was zero difference in fuel consumption. I have heard the same goes for the fuel management system from almost everyone who had the AFM system. I am new to all this so there may be something I'm missing.

[Thomcat]

24 minutes ago, BamX31 said:

I notice it every time I drive the truck and hate it. I can hear and feel when the thing drops cylinders. While having dropped cylinders waiting the 3-5 seconds it takes to figure out what to do when I want to mash the peddle to take off or pass a car is just ridiculous. I will be having this option looped out of the program if Range does not come up with something soon. Like the auto stop/start function. It is a gimmick. I ran two tanks with and two tanks without making the same exact trips and there was zero difference in fuel consumption. I have heard the same goes for the fuel management system from almost everyone who had the AFM system. I am new to all this so there may be something I'm missing.

I suggest you take it in for service. I for one don't notice the DFM operation at all  - totally seamless - not so for AFM which was not really annoying, but noticeable.

 

Evidently you must have one with a "mentally challenged" processor. No 3-5 seconds delay with mine, as soon as I mash the accelerator it instantly drops down one or two gears and simultaneously takes off like a bat outta hell on all 8 cylinders..

 

I doubt if the switch from AFM to DFM was ever done for fuel consumption more likely $$$ to make a cheaper more dependable engine and reduce costs of warranty servicing. Same basic push rod small block engine but less parts and reapplication of existing parts. Collapsible lifters on all 8 cylinders instead of 4 with and 4 without, oil control solenoids mounted directly in the block for all 8 cylinders instead of an intermediate LOMA manifiold w/ oil screen in the valley with the solenoids controlling only 4 AFM cylinders, and best of all no more AFM valve dumping excess oil from the LOMA into the sump which is the Achilles heel for the AFM system causing excess oil buildup on dead (primarily the #1) cylinders. GM must have spent a fortune chemically "cleaning", engines, replacing lifters, replacing pistons, refitting new valve covers, installing shields over the AFM discharge valve, etc under warranty when they became oil burners. DFM engines are basically the relocation of some parts and elimination of the troublesome ones specific to AFM.......only difference being a a new faster and more complex computer processor capable of monitoring and controlling multiple firing sequences instead of the "slower" AFM one capable of just two stages.

 

Basically for longevity and durability makes sense to have all 8 cylinders firing under then same conditions rather than the same 4 with and 4 without. Why didn't GM start out with simpler DFM instead of AFM...probably for the same reason your computer is not running on the same processor as the one used in '07. Are DFM engines better - I hope so - may or may not, only time will tell -  but for certain won't have the problems or quirks specific to AFM engines.

[Thomcat]

17 hours ago, DuRsT said:

I was thinking the same thing.  I've never seen anyone this passionate about DFM lol

After owning many AFM engines since my '07 Avalanche you can believe that I well researched this before buying another one. And to respond to a similar post I don't work for Chevy, nor anyone else. Retired at 56 with pensions, annuities and Social Security, "What me worry?" Just too much time on my hands to research matters and participate in posts. Another pastime is to visit every car dealer within 50 miles and test ride ever model in their inventory.....I may not know who makes the be3st cars, but I do know who makes the best coffee!

 

But a lot of it could be just basic living the difference between appreciating where you come from and where you are now...... appreciating the appearance ride and handling of any '19 vehicle. Want a real complaint try driving a '53 Chevy with 3-on-the-tree non synchromesh Muncie with 3 finger clutch with only options a tube AM radio and heater......then you'll have something to cry about, crawling under the car to free up the shift rods or pulling off a 10 lb POS oil bath air cleaner in sub zero weather to jamb a screwdriver into the caveman era choke to get it to start, or try climbing a hill in a rainstorm with vacuum operated wipers balancing power with wiper speed. I haven't had a car stall out in traffic in over 20 years. So I don't cry about every little piece of nonsense like a door latch that needs adjustment, easier to just do the simpler things myself or live with it. So unless it's a no-go situation, not much to really complain about----- roof pops?

 

Or, maybe just Karma - no window leaks - engine and tranny smooth as silk - paint flawless, leather comfortable, everything A-OK.

 

[BamX31]

49 minutes ago, Thomcat said:

I suggest you take it in for service. I for one don't notice the DFM operation at all  - totally seamless - not so for AFM which was not really annoying, but noticeable.

 

Evidently you must have one with a "mentally challenged" processor. No 3-5 seconds delay with mine, as soon as I mash the accelerator it instantly drops down one or two gears and simultaneously takes off like a bat outta hell on all 8 cylinders..

 

I doubt if the switch from AFM to DFM was ever done for fuel consumption more likely $$$ to make a cheaper more dependable engine and reduce costs of warranty servicing. Same basic push rod small block engine but less parts and reapplication of existing parts. Collapsible lifters on all 8 cylinders instead of 4 with and 4 without, oil control solenoids mounted directly in the block for all 8 cylinders instead of an intermediate LOMA manifiold w/ oil screen in the valley with the solenoids controlling only 4 AFM cylinders, and best of all no more AFM valve dumping excess oil from the LOMA into the sump which is the Achilles heel for the AFM system causing excess oil buildup on dead (primarily the #1) cylinders. GM must have spent a fortune chemically "cleaning", engines, replacing lifters, replacing pistons, refitting new valve covers, installing shields over the AFM discharge valve, etc under warranty when they became oil burners. DFM engines are basically the relocation of some parts and elimination of the troublesome ones specific to AFM.......only difference being a a new faster and more complex computer processor capable of monitoring and controlling multiple firing sequences instead of the "slower" AFM one capable of just two stages.

 

Basically for longevity and durability makes sense to have all 8 cylinders firing under then same conditions rather than the same 4 with and 4 without. Why didn't GM start out with simpler DFM instead of AFM...probably for the same reason your computer is not running on the same processor as the one used in '07. Are DFM engines better - I hope so - may or may not, only time will tell -  but for certain won't have the problems or quirks specific to AFM engines.

I have had it in for the brake recall and brought this up. They told me everything was fine and the delay was normal. I have read so much about these two different systems my head hurts. It does seam the largest issues was with not alternating dead cylinders vs it always being the same ones. 

[DuRsT]

I have to agree that when tooling around town it makes the truck feel sluggish until you mash the go-pedal.  Then it wakes up and accelerates very, very well for a truck of this size.

 

To me, adding an aftermarket exhaust exacerbates all of this because you can now hear all of the different 'modes' the engine is going through with 10 different gears and varying degrees of cylinder participation depending upon load response. 

 

All in all, it is something I have to get accustomed to as this is the way of the future, the linear and confident pull of a V8 truck pulling on all cylinders all the time is something from the past. 

[foghorn23]

 

23 minutes ago, DuRsT said:

All in all, it is something I have to get accustomed to as this is the way of the future, the linear and confident pull of a V8 truck pulling on all cylinders all the time is something from the past. 

Not a Ford fanboy by any stretch of the imagination, but that is one of the most appealing things about their "new" 7.3 Godzila engine in the super duty trucks.  Old fashioned push rod design, no over head cams with miles of timing chains and multiple guides, no cylinder deactivation of any kind, no direct injection- multi port injected.  If they weren't so much more truck than I need, I'd be tempted to go drive one. 430 HP and 475 ft/lbs of old school V8 grunt!  

 

 

Edited February 16, 2020 by Foghorn19

[DuRsT]

1 minute ago, Foghorn19 said:

Not a Ford fanboy by any stretch of the imagination, but that is one of the most appealing things about their "new" 7.3 Godzila engine in the super duty trucks.  Old fashioned push rod design, no over head cams with miles of timing chains and multiple guides, no cylinder deactivation of any kind, no direct injection- multi port injected.  If they weren't so much more truck than I need, I'd be tempted to go drive one. 430 HP and 475 ft/lbs of old school V8 grunt!  

 

 

Have to agree, I was kind of looking forward to them coming out myself but ended up pulling the trigger on the Sierra beforehand because I got pissed with Ford over the OHC design flaws that have been in place for YEARS.  The old 6.2 was one of the best engines they made, and the 5.0 was not a bad engine at all either but was lacking low-end grunt for a truck IMO. 

 

That 7.3 should be interesting given that they are returning to a pushrod motor, and tempting to anyone that likes 'old-school'. 

[Cpl_Punishment]

53 minutes ago, Foghorn19 said:

 

Not a Ford fanboy by any stretch of the imagination, but that is one of the most appealing things about their "new" 7.3 Godzila engine in the super duty trucks.  Old fashioned push rod design, no over head cams with miles of timing chains and multiple guides, no cylinder deactivation of any kind, no direct injection- multi port injected.  If they weren't so much more truck than I need, I'd be tempted to go drive one. 430 HP and 475 ft/lbs of old school V8 grunt!  

 

 

GM's new 6.6 gasser in the HDs has cylinder deactivation? I honestly can't remember; it's been a while since I read anything about that engine. I recall that it incorporates some features from the 1500 engines but I didn't think DFM was one of them. 

[blckblt]

I don't notice any sluggish behavior or even notice when it does it's thing with my 6.2 and DFM.  I press the gas and truck wants to launch every time from any speed.  I have yet to "really" get on the throttle as I am just finishing the break in period.  I didn't notice it in the 19 TB that test drove a year ago that had the 5.3 but that was only about 20 miles.

 

Now the auto stop is another thing, while not super slow to start back up it is noticeable.  About 50% of the time I forget to turn it off until after the first time the truck shuts off.  Does this even make a MPG difference?

[Cpl_Punishment]

19 hours ago, blckblt said:

I don't notice any sluggish behavior or even notice when it does it's thing with my 6.2 and DFM.  I press the gas and truck wants to launch every time from any speed.  I have yet to "really" get on the throttle as I am just finishing the break in period.  I didn't notice it in the 19 TB that test drove a year ago that had the 5.3 but that was only about 20 miles.

 

Now the auto stop is another thing, while not super slow to start back up it is noticeable.  About 50% of the time I forget to turn it off until after the first time the truck shuts off.  Does this even make a MPG difference?

Probably depends on where you live. Whichever city engineer timed the lights on my commute apparently decided that everyone who's making their way from our suburb towards downtown needs to stop for 5 minutes every few hundred yards to watch no traffic going across the intersection the other direction. Might be more useful for me than for someone who gets on the interstate and doesn't stop until they're at work 

[MacLaren]

I'm just fine and dandy with DFM

Thos is with 89 octane

I might possible could've squeezed 600 miles out of a tank! That's incredible compared to 375 miles as before on my 07 Classic, that got a damn respectable 17/19