DFM disable

BamX31 · February 12, 2020

Hello everyone. After poking around on here for a while Range seams to be the only manufacturer in this market. Did I by chance over look someone? I messaged them and after several days someone finally got back with me stating it would be at least a few months before something could be ready.

Thomcat · February 12, 2020

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.

ILSilverado · February 12, 2020

Yea they have been poking around with that DFM version for a year now. I do have the AFM version in my Corvette and it works great.

Edited February 12, 2020 by ILSilverado

ILSilverado · February 13, 2020

4 hours ago, 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.

Because the DFM will eventually ruin your transmission. The DFM when engaged causes a vibration in the transmission eventually causing the A8 transmission to fail. Corvette owners with the 8 speed have been experiencing this for years now. I had one fail with less than 5000 miles on it. Just Google it.

Edited February 13, 2020 by ILSilverado

Thomcat · February 13, 2020

10 hours ago, ILSilverado said:

Because the DFM will eventually ruin your transmission. The DFM when engaged causes a vibration in the transmission eventually causing the A8 transmission to fail. Corvette owners with the 8 speed have been experiencing this for years now. I had one fail with less than 5000 miles on it. Just Google it.

According to the chart in the first link Corvettes use AFM, not DFM. And as for the 8 speed of a few years ago running that hydroscopic Dextron that screwed with interior components ....yes.... problems, but not necessarily caused by AFM , certainly impossible by DFM, and not shared with later trannys running the new Mobil1 HP fluid from the beginning, or 100% changed soon after operation before it could cause an irreversible effect on tranny operation. That's purposely why I bought a post 3/19 production 8 speed....to assure it came from the factory with a belly full of Mobil 1 Synthetic LV ATF HP! And no engine vibration orshudder in my tranny running that combo. So, no need to be a guinea pig trying one out on a new advanced system with different operations and processors.

If you're talking AFM, yes, they're crap no matter what you throw them in....they've been kludging them since my '07 Avalanche...and the driver (not just the tranny) can feel the AFM kick in .. ..oil ring clogging, wearing and turning into oil burners and a POS valve cover that sucks oil from the upper end and dumps in the induction system, that's why you need a catch can......nasty harmonic for the same 4 dead cylinders at a specific speed, etc. Numerous TSB modifications including 3 versions of revised valve covers, two for shielding of the AFM discharge valve in the sump and numerous design revisions to the collapsible valve lifters....all around an engine designed for potential problems from the start with the same 4 of the 8 cylinders operating dead yet still pulling oil onto their colder cylinder walls overloaded with oil spray from the AFM discharge valve in the sump. I always used the range device AFM defeat device on long trips because continued operation with the same four dead, colder cylinders cruising on a long trip for a prolonged period wasn't good.

Couldn't wait to dump the fully kludged up '16 AFM in favor of the completely redesigned DFM arrangement eliminating the OLM altogether, new domed valve cover w/oil straining baffles to eliminate the need for a catch can, no more oil ring clogging AFM discharge valve in the sump, rotation of dead cylinder patterns to even out cylinder temperatures and not generate the same frequency vibration harmonic each time in operation. Actual performance of the same size DFM vs. AFM is remarkable..... control of the complex system required development of an advance processor to always keep the engine at full time peak performance. Seems GM finally relegated the AFMs to the retirement home, using up all old stock and you won't be seeing them on newer production vehicles.

Doesn't take an engineering degree to review the docs and realize DFM is a whole different animal without the same AFM flaws.

https://gm-techlink.com/?p=11880

https://gmauthority.com/blog/gm/general-motors-technology/general-motors-propulsion-technology/general-motors-dynamic-fuel-management-cylinder-deactivation-technology/

https://gm-techlink.com/?p=11127

Edited February 13, 2020 by Thomcat

ILSilverado · February 13, 2020

1 hour ago, Thomcat said:

According to the chart in the first link Corvettes use AFM, not DFM. And as for the 8 speed of a few years ago running that hydroscopic Dextron that screwed with interior components ....yes.... problems, but not necessarily caused by AFM , certainly impossible by DFM, and not shared with later trannys running the new Mobil1 HP fluid from the beginning, or 100% changed soon after operation before it could cause an irreversible effect on tranny operation. That's purposely why I bought a post 3/19 production 8 speed....to assure it came from the factory with a belly full of Mobil 1 Synthetic LV ATF HP! And no engine vibration orshudder in my tranny running that combo. So, no need to be a guinea pig trying one out on a new advanced system with different operations and processors.

If you're talking AFM, yes, they're crap no matter what you throw them in....they've been kludging them since my '07 Avalanche...and the driver (not just the tranny) can feel the AFM kick in .. ..oil ring clogging, wearing and turning into oil burners and a POS valve cover that sucks oil from the upper end and dumps in the induction system, that's why you need a catch can......nasty harmonic for the same 4 dead cylinders at a specific speed, etc. Numerous TSB modifications including 3 versions of revised valve covers, two for shielding of the AFM discharge valve in the sump and numerous design revisions to the collapsible valve lifters....all around an engine designed for potential problems from the start with the same 4 of the 8 cylinders operating dead yet still pulling oil onto their colder cylinder walls overloaded with oil spray from the AFM discharge valve in the sump. I always used the range device AFM defeat device on long trips because continued operation with the same four dead, colder cylinders cruising on a long trip for a prolonged period wasn't good.

Couldn't wait to dump the fully kludged up '16 AFM in favor of the completely redesigned DFM arrangement eliminating the OLM altogether, new domed valve cover w/oil straining baffles to eliminate the need for a catch can, no more oil ring clogging AFM discharge valve in the sump, rotation of dead cylinder patterns to even out cylinder temperatures and not generate the same frequency vibration harmonic each time in operation. Actual performance of the same size DFM vs. AFM is remarkable..... control of the complex system required development of an advance processor to always keep the engine at full time peak performance. Seems GM finally relegated the AFMs to the retirement home, using up all old stock and you won't be seeing them on newer production vehicles.

Doesn't take an engineering degree to review the docs and realize DFM is a whole different animal without the same AFM flaws.

https://gm-techlink.com/?p=11880

https://gmauthority.com/blog/gm/general-motors-technology/general-motors-propulsion-technology/general-motors-dynamic-fuel-management-cylinder-deactivation-technology/

https://gm-techlink.com/?p=11127

AFM and DFM are the same thing other than DFM has the ability to go down to one cylinder whereas AFM 4 is the lowest. You still get an uneven frequency vibration while in reduced cylinder mode that will eventually ruin the transmission. This is why my 2020 is a diesel and not a V8.

amxguy1970 · February 13, 2020

12 hours ago, ILSilverado said:

Because the DFM will eventually ruin your transmission. The DFM when engaged causes a vibration in the transmission eventually causing the A8 transmission to fail. Corvette owners with the 8 speed have been experiencing this for years now. I had one fail with less than 5000 miles on it. Just Google it.

:rollin: Thanks for that, I needed a laugh to start the morning!

People will believe anything on the internet and around here any type of problem they immediately take aim at AFM. Transmission problems, AFM, AC went out, AFM, axle failure, AFM, power seat switch, must be AFM. People for some reason are against saving fuel. This isn't the same AFM that people heard troubles with during the first go around in the mid 2000's. Oil consumption issues and lifter failures are mostly a thing of the past except for some rogue issues. With the new DFM having 16 lifters as opposed to 8 with AFM those who are against must be throwing a fit...

Tyler

ILSilverado · February 13, 2020

46 minutes ago, amxguy1970 said:

Thanks for that, I needed a laugh to start the morning!

People will believe anything on the internet and around here any type of problem they immediately take aim at AFM. Transmission problems, AFM, AC went out, AFM, axle failure, AFM, power seat switch, must be AFM. People for some reason are against saving fuel. This isn't the same AFM that people heard troubles with during the first go around in the mid 2000's. Oil consumption issues and lifter failures are mostly a thing of the past except for some rogue issues. With the new DFM having 16 lifters as opposed to 8 with AFM those who are against must be throwing a fit...

Tyler

My information comes right from one of the Corvette racing team engineers I trust him, you can believe what you want. Play this video they will talk about why they had to stiffen the toque tube by 300% when they went with cylinder deactivation.

Edited February 13, 2020 by ILSilverado

Thomcat · February 14, 2020

7 hours ago, ILSilverado said:

My information comes right from one of the Corvette racing team engineers I trust him, you can believe what you want. Play this video they will talk about why they had to stiffen the toque tube by 300% when they went with cylinder deactivation.

Here's your original post..... "Because the DFM will eventually ruin your transmission. The DFM when engaged causes a vibration in the transmission eventually causing the A8 transmission to fail. Corvette owners with the 8 speed have been experiencing this for years now." Whole argument is a non sequitur because no Corvette was ever equipped with a DFM engine.. Only AFMs were installed in many Corvettes. So there is no way an engine introduced into production in '19 Silverados ever caused any damage for a number of years to any tranny in any Corvette or any other pre '19 GM for that matter.

Assuming a vibratory harmonic can damage a transmission. Instead of screwing around with Google brush up on Physics. All rotating engines produce a vibratory harmonic at a specific frequency(ies) being a function of engine configuration and number of cylinders and rpm. AFMs running on 4 cylinders produce the same vibratory harmonic at the same rpm and frequency every time when in 4 cyl. operation which is claimed to be the problem. DFMs produce varying harmonics at different frequencies depending upon the number of cylinders in use at any specific rpm, i.e. not the same harmonic all the time and not for any prolonged period and not at the same rpm. That's why you can feel an AFM transition but not DFM transitions and you cannot translate any AFM vibratory problems to a DFM engine..

So what's the big deal of operating on one cylinder when braking to a stop....it's not like you need the power to coast? Sort of like closing the throttle on a carb cutting all fuel flow from the main jets and operating on only a trickle from a bleed channel below the throttle plate to prevent a stall..

The weak torque tube concept is not comparing apples to oranges, more like comparing apples to coconuts. Can't see what possible application in stiffening a torque tube on a fiberglass car that weighs little more than a Pinto with an engine well in excess of typical hp/weight ratio and a helluva lot more torque has to do with application of the concept to the same tranny in a larger, heavier steel full size truck with a different design motor? Just a wild guess but I suspect the torque tube in a Corvette weighs a lot less and has a lot less strength than the main driveshaft in a Silverado (and transfer case) anyway.

KARNUT · February 14, 2020

What!? Wait, the vette has cylinder deactivation too!? That’s just wrong. Cross that off my bucket list.

snork · February 14, 2020

4 minutes ago, KARNUT said:

What!? Wait, the vette has cylinder deactivation too!? That’s just wrong. Cross that off my bucket list.

nice thing about the C7 corvette is you can deactivate the dfm by selecting sport or track mode

KARNUT · February 14, 2020

5 minutes ago, snork said:

nice thing about the C7 corvette is you can deactivate the dfm by selecting sport or track mode

Shouldn’t have it at all. My last Z-28 (94) got 24mpg. I didn’t buy it for fuel mileage. I imagine the vette dose well without it. When I bought performance vehicles fuel mileage wasn’t a factor.

OnTheReel · February 14, 2020

20 minutes ago, KARNUT said:

Shouldn’t have it at all. My last Z-28 (94) got 24mpg. I didn’t buy it for fuel mileage. I imagine the vette dose well without it. When I bought performance vehicles fuel mileage wasn’t a factor.

Let’s not forget the dumb skip shift feature too. Had to get into the habit of winding out 1st, lest I got forced into 4th. How’s that for fuel economy?

Easily defeated too though. Just never got around to it on my 96.

Thomcat · February 14, 2020

11 hours ago, KARNUT said:

What!? Wait, the vette has cylinder deactivation too!? That’s just wrong. Cross that off my bucket list.

LT1 and LT4 have AFM.........LT5 has no cylinder deactivation hardware.

ILSilverado · February 14, 2020

14 hours ago, snork said:

nice thing about the C7 corvette is you can deactivate the dfm by selecting sport or track mode

Nope not with the automatic. Only the M paddle shift mode disengages AFM. On the manual it’s off unless it’s in eco mode. This is why the Range device is so popular with Corvette owners because over time the added vibration and oscillation from reduced cylinder mode destroys the toque converters.

Edited February 14, 2020 by ILSilverado