How is the DFM working for you?

[steve841]

34 minutes ago, Aycock1987 said:

Aside from the mpg... which truck towed better from a confidence standpoint?

 

Honestly, cant tell much of a difference..

 

I tow three trailers ...  9000lb boat, 2500lb boat and a enclosed trailer about 2000lbs.  

[swathdiver]

9 hours ago, steve841 said:

 

Me too ...  but my last truck was the 6 speed .. ran about 2200 RPMs at 70mph.

 

The 19 runs at around 1800 RPMs at 70mph.

 

Everything about that metric makes you think the 19 should kill the old truck in mileage.  Its simply not the case.

 

The only other major difference is the 19 has 22" wheels vs the old one with 20"

Next time, hold 2200 rpms @ 70 mph in a lower gear and see what she averages mpg wise.

 

It seems from reading these posts that even with DFM and the 400 pound weight loss that that huge front end is what reduced their economy compared with the previous generation.

[Sierradude]

That’s why GM always kept their trucks smaller then Ford and Ram on the exterior. How much bigger do these trucks need to get? It’s rediculous!

 

[Stex]

Too early to tell is my bet. Need more engines with miles on them. AFM worked to till the miles started adding up. Note that the collapsing lifters are back along with levers etc.... DFM, what could go wrong?

 

An electromechanical system deactivates and reactivates all 16 of the engine’s hydraulic valve lifters, controlling valve actuation. The system uses solenoids to deliver oil pressure to control ports in the lifters, which activate and deactivate the lifters’ latching mechanisms. When a cylinder is deactivated, the two-piece lifters effectively collapse on themselves to prevent them from opening the valves. When the cylinder is reactivated, solenoids send an oil pressure signal to the control ports on the lifters and the latching mechanism restores normal function, allowing the valves to open and close.

[O Town Denali]

On 12/23/2018 at 8:21 AM, keith4x4dbl said:

 

Do you think the DFM is disabled on these trucks until you purchase them? This is a big question because it would speak towards unfair sales practices?

 

No.  I wish it was that easy to disable.

As posted, cannot tell a difference operationally.

Time will tell if it is reliable mechanically.

 

My 2016 6.2 suffered a collapsed lifter at 66K miles ( 28 months).  Just out of factory warranty.  Luckily I had an extended protection plan.

[Stex]

6 hours ago, O Town Denali said:

No.  I wish it was that easy to disable.

As posted, cannot tell a difference operationally.

Time will tell if it is reliable mechanically.

 

My 2016 6.2 suffered a collapsed lifter at 66K miles ( 28 months).  Just out of factory warranty.  Luckily I had an extended protection plan.

Yes you where. The repair is expensive. Heads have to come off. And the cam can be ruined. Sounds like the same lifters in the DFM? Not sure. I am real gun shy on GMs cylinder deactivation for good reason. For all with DFM, hope it works well.

[FirstAscent]

I haven’t noticed it at all which is good, otherwise it’d be annoying. Can’t believe it’s doing much for mpg though, my last tank of gas averaged a measly 12.5 mpg which included a trip to the mountain (hwy miles) and then the rest city miles. The tank before that was only 14.5, and I was babying it too trying to see how well it did with “normal” driving. Not impressed yet.

Only 500 miles on the truck so far, maybe it’ll get better haha, heck I can get 15-17 mpg on the supercharged Jag and Not taking it easy on the pedal
But yeah I don’t notice the DFM at all on my 5.3

[Robwcormack]

Does anyone know of circumstances when the DFM wont function?  I.e.pulling trailer, sport mode, etc?

 

Also, has anyone heard real world aftermarket exhaust one one of these yet?  I think corsa and flowmaster are the only ones available right now.  Curious if the DFM makes the same horrible sound the AFM did.  

[2cyclemech]

The Dfm in my 2019 silverado is terrible trk been at dealer for 1month an still same shudder at 30-65 mph with lite throttle pressure to just maintain speed trk has 14k on it mostly highway miles they changed the trans fluid as a update an Checked converter lock up  reflashed ecm with most recent updates Situations been escalated all the way up to GM engineering in

[Thomcat]

On 2/3/2019 at 1:16 PM, Stex said:

Too early to tell is my bet. Need more engines with miles on them. AFM worked to till the miles started adding up. Note that the collapsing lifters are back along with levers etc.... DFM, what could go wrong?

 

An electromechanical system deactivates and reactivates all 16 of the engine’s hydraulic valve lifters, controlling valve actuation. The system uses solenoids to deliver oil pressure to control ports in the lifters, which activate and deactivate the lifters’ latching mechanisms. When a cylinder is deactivated, the two-piece lifters effectively collapse on themselves to prevent them from opening the valves. When the cylinder is reactivated, solenoids send an oil pressure signal to the control ports on the lifters and the latching mechanism restores normal function, allowing the valves to open and close.

It's not a matter of what could go wrong with the DFM or even a matter of better gas mileage.....it is a matter of designing a less complicated less trouble prone engine.

 

AFM systems were an abortion from the beginning. Took a perfectly good V8 or V6 design, and modified it to include an intermediate lifter oil manifold assembly (LOMA) to manage oil pressure in conjunction with collapsible lifters, and control of induction on half the cylinders in a V engine with the other half under normal operation. Genius design included a valve which discharged the redirected LOMA oil from the 4 dead cylinders into the sump. A nightmare design with a time bomb for owners of the '07 - 1/'11 AFMs. Discharge oil from the LOMA deposited on walls of the dead cylinders clogging oil control rings in conjunction with oil through the PCV system causing oil burning problems. GM went through numerous chemical cleaning attempts on oil burning engines with clogged/frozen rings and in many cases had to resort to piston ring replacement.......only while still under warranty. Went through engine modification kludges including new valve covers with relocated PCV pickup to the eventual shield placed over the discharge port in the sump on post 1/'11 production. Appears GM dumped the last of the kludged up V8 AFMs in their lower line '19 production; '20 V8s come standard with the DFM.

 

AFM uses the same two piece lifters on the 4 AFM cylinders and uses electromechanical control not only to feed the collapsible lifters but to determine when to redirect oil back into the sump. Which would you rather have?.......control of oil pressure to all 8 cylinders by solenoids mounted directly in the block, or oil control of 4 cylinders by solenoids mounted in an add on trouble prone LOMA manifold mounted in the in valley with no oil control over the remaining 4 cylinders. Simpler design using increased computer control, less parts to break and no chance of a clogged piston rings or LOMA filter in the rear of the engine. Other changes include a complete redesign of the valve covers and PCV system to greatly reduce the amount of oil vapor entering the PCV system which should eliminate the need for an aftermarket "catch can" system.

 

Had AFMs in my Avalanches and '16 and glad to be rid of them! Totally seamless system. In fact the engine runs so damned smooth that sometimes I think that I forgot to hit the auto stop button.

 

Only way to tell is to look at the tach and oil gauge!!Which would you rather have....read the articles and determine for yourself?

 

https://techlink.mynetworkcontent.com/wp-content/uploads/2018/09/GM_TechLink_16_Mid-August_2018.pdf

 

https://techlink.mynetworkcontent.com/wp-content/uploads/2019/08/GM_TechLink_15_August_2019.pdf

 

 

 

[Wiggums]

My gas mileage has been fantastic and I can barely feel the DFM, it has to be on the highway and getting it up to speed then you can feel it kicking in slightly. I try not to move my foot at all and gas mileage has been remarkable. Very happy with the gas mileage.

[Thomcat]

22 hours ago, 2cyclemech said:

The Dfm in my 2019 silverado is terrible trk been at dealer for 1month an still same shudder at 30-65 mph with lite throttle pressure to just maintain speed trk has 14k on it mostly highway miles they changed the trans fluid as a update an Checked converter lock up  reflashed ecm with most recent updates Situations been escalated all the way up to GM engineering in

Those are not DFM engine concens, they are transmission concerns. Early  8 speeds used hydroscopic Dextron instead of Mobil 1 HD fluid made standard on post 3/1/19 production. And damage done to the tranny or torque converter may not be corrected by a flush and refill with the correct fluid.

[2cyclemech]

Why then when The tech That rode with me an he shut off Dfm with his lap top the problem wasnt there til he turned it back  on An it only does it when it cancels 1  cyl when it cancels 2 at time no shudder i am fed up with chevy at this point should stayed with my nissan titan 

[2016 Sierra Owner]

On 12/12/2019 at 8:10 AM, 2cyclemech said:

The Dfm in my 2019 silverado is terrible trk been at dealer for 1month an still same shudder at 30-65 mph with lite throttle pressure to just maintain speed trk has 14k on it mostly highway miles they changed the trans fluid as a update an Checked converter lock up  reflashed ecm with most recent updates Situations been escalated all the way up to GM engineering in

What is the trim level of your Silvy? What engine and trans have you got? Info like that helps people reading your comments.

[2cyclemech]

LT All Star edition 5.3 eco L84 8speed trans 14K purchased in March of 19