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cmonster

Ordered 21 RST An have a break in question

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Ordered 21 RST 6.2, Z71 GM exhaust, intake, 2” lift an a power up tailgate. The DFM I don’t like the idea of cylinders cutting off, will tow mode or sport mode keep them from Activating? and is it ok to stay in these modes forever. Heard 10sp has 3 od gears what shift point keeps the DFM from kicking in, not concerned about gas or mileage. Coming from 5.3 Alpha Hummer AWD. only concerned about all lifters an ****** getting oil 

Edited by cmonster

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Tow haul or L9 should keep the dfm disabled. You could also buy a range unit if available for your motor/tranny combo but why waste that money if twisting a knob takes a second to do


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Recently broke-in my 6.2 with a 10 speed. I found the truck liked to run 1300-1500 rpm. Around town driving I could hit 3500 rpms at a stop light, but that quickly gets you to the speed limit. Then 1300-1500 rpms. Even on the highway, 75-80 mph would only get me to 1800 rpm.

I found running in tow mode would vary the rpms 1500-2500 rpms, 3500-4500 at takeoff. Sport mode was not as effective at varying the rpms.

Note: I always disable the auto engine shutoff.

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Drive like you stole it, that's how you break stuff in.

 

The local construction company by my house gets new trucks in all the time, they will have 20 miles on them and it's hooked up to a gooseneck trailer on the heavy dutys or a normal trailer for the half tons. Then 200k miles later it's getting replaced, needless to say they don't break anything in with a feather foot. AFM /DFM working like it should.

 

As said above you can buy something to disable the DFM or run it in L9 all the time. I honestly wouldn't even worry about it. Lifters and other crap can still fail even if it's disabled.

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Tow/Haul/Sport Mode does not deactivate DFM. If you don't like the idea of cylinders cutting off maybe you should have gotten a different truck. You can do a Range, mine works but I get a check engine light every once in a while. I think you can tune your truck but it's gonna be in the couple $$$$'s. 

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The only thing you can do to disable the AFM is to put the truck in L9.  IDK why people are so attainment about disabling the cylinder deactivation, the lifters are still in your engine, just drive the truck.

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The only thing you can do to disable the AFM is to put the truck in L9.  IDK why people are so attainment about disabling the cylinder deactivation, the lifters are still in your engine, just drive the truck.

I *THINK* I read the issue is the lifters have a tendency to turn 90° while they’re deactivated putting the roller in a position where it can’t roll anymore. Then they break when reactivated.


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I just pulled a 30 ft 6,000 lb travel trailer over 350 miles with my 5.3 10 speed DFM. I used tow/haul mode and didn't have any issues. The only thing I did prior to towing was not tow during the first 500 miles of breaking in the truck per the owner's manual and I performed the truck's first oil change prior to towing per the manual as well.  I drive the truck with DFM and start/stop activated and use tow/haul mode.  I think the truck is engineered very well and also believe it should last a long time so long as I use it as intended and maintain it. 

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On 9/10/2020 at 9:48 AM, Jav_eee said:


I *THINK* I read the issue is the lifters have a tendency to turn 90° while they’re deactivated putting the roller in a position where it can’t roll anymore. Then they break when reactivated.


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That’s right and why I want them under load all the time, guess I’ll just keep the rev’s up and manual shift 

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AFM vs DFM

 

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

 

Active Fuel Management/Dynamic Fuel Management on GM Models

August 9, 2019

Active Fuel Management (AFM) or Dynamic Fuel Management (DFM) is available on a number of recent GM models to help improve fuel economy, including 2014-2019 Corvette, Silverado LD, Sierra Limited; 2015-2019 Escalade, Suburban, Tahoe, Yukon; 2016-2019 CTS-V, Camaro; 2019 Silverado 1500, Sierra 1500; 2020 Silverado 2500/3500 and Sierra 2500/3500 models.

 

Active Fuel Management

AFM was designed to provide maximum fuel economy under light load driving conditions by deactivating the lifters on specific cylinders. On V8 engines, half of the cylinders are deactivated and on V6 engines, two of the cylinders are deactivated.

Under certain operating conditions, the Engine Control Module (ECM) commands the cylinder deactivation system to deactivate engine cylinders 1, 7, 6, and 4 on V8 engines or to deactivate engine cylinders 3 and 6 on a V6 engine. The engine will operate on all cylinders during engine starting, engine idling and medium-to-heavy throttle applications.

The Lifter Oil Manifold Assembly (LOMA) is only used on AFM applications.

 

Dynamic Fuel Management

DFM is the next generation in cylinder deactivation systems. It features AFM technology with the additional ability to deactivate any combination of cylinder valves to optimize fuel consumption. The control of every cylinder event allows peak efficiency to be obtained throughout the range of engine operation. (Fig. 15)

 

F15-AFM-v-DFM-infographic.pngFig. 15

 

By extending cylinder deactivation to all cylinders, DFM allows for a large variety of firing sequences. DFM can have rotating cylinder deactivation patterns, such as 1/5, 1/3, 2/5, or 2/3, as well as fixed patterns, such as 1/4, 1/2, or 3/4. For rotating patterns, which are only available on small block engine (L84,L87), the cylinders being deactivated can change with each subsequent engine cycle. Transitions between firing sequences is done in a continuous fashion, making the transitions seamless and transparent to the driver.

Oil Control Valves (OCV), only used on small block engines, replace the LOMA. OCVs provide faster response times than the LOMA and are required for DFM. OCVs also are used on L82 engines with AFM.

 

AFM/DFM Usage
Model AFM VLOM 4 Cylinder Deactivation DFM OCV FDFM None Notes
CTS-V 6.2L LT4 Yes Yes No No   Always active
Camaro 6.2L LT1 Yes Yes No No   Automatic only. AFM not active with manual trans
Camaro 6.2L LT4 Yes No No No   Has the hardware, not active
Corvette 6.2L LT1, LT4 Yes Yes No No   Auto trans active, manual trans active in ECO only
Corvette 6.2L LT5 No No No No Yes No hardware on LT5
Escalade 6.2L L86 Yes Yes No No    
Suburban/Tahoe/
Yukon 5.3L L83, 6.2L L86
Yes Yes No No    
Silverado LD/Sierra LD 5.3L L83, 6.2L L86 Yes Yes No No    
Silverado/Sierra 4.3L LV3 Yes Yes No No    
Silverado 1500/Sierra 1500 5.3L L82 No Yes Yes No    
Silverado 1500/Sierra 1500 5.3L L84, 6.2L L87 No No Yes Yes    
Silverado/Sierra HD 6.6L L8T No No No No   No hardware on L8T
Express/Savana 4.3L LV1 No No No No   No hardware on LV1
Express/Savana 6.6L L8T No No No No   No hardware on L8T

 

 

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I really don't understand the big deal over it. Mine's fine with the DFM. If the truck is on a hill or knows I'm pulling something ,it will not activate. You can barely feel it!

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I really don't understand the big deal over it. Mine's fine with the DFM. If the truck is on a hill or knows I'm pulling something ,it will not activate. You can barely feel it!


Reliability and longevity is the big deal.


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