Chevy 2026 Trucks still have Dynamic Fuel Management ( DFM)

[CKN]

So how about it Bitogers. GM is still using DFM in spite of all the hand wringing at BITOG. Has something changed with the system?

Mods, I did screen shots from GM to show they are still using the system.

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Of course the 2.7 and the 5.3 (2026) uses different systems. Not sure about the others. And yet again-the 2027's and supposed to be different as well.
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GM is reportedly developing a new V8 cylinder deactivation system for the 2027 Silverado and Sierra that aims to resolve the lifter failure issues associated with the current Dynamic Fuel Management (DFM) technology.

According to patent filings and reports, this next-generation system will likely utilize rocker arms with hydraulic oil to disengage valve actuation, rather than relying on the problematic collapsible lifters used in previous 5.3L and 6.2L engines.

So yes-they are changing.

 

[grasscutter]

Of course the 2.7 and the 5.3 (2026) uses different systems. Not sure about the others. And yet again-the 2027's and supposed to be different as well.
-
GM is reportedly developing a new V8 cylinder deactivation system for the 2027 Silverado and Sierra that aims to resolve the lifter failure issues associated with the current Dynamic Fuel Management (DFM) technology.

According to patent filings and reports, this next-generation system will likely utilize rocker arms with hydraulic oil to disengage valve actuation, rather than relying on the problematic collapsible lifters used in previous 5.3L and 6.2L engines.

So yes-they are changing.

Why can't they just come out and admit that the whole venture was a bad idea?

Find some other way to improve fuel economy without of shutting half the engine off.

 

[4wd]

Why can't they just come out and admit that the whole venture was a bad idea?

Find some other way to improve fuel economy without of shutting half the engine off.

What was - CAFE ?

 

[CKN]

Why can't they just come out and admit that the whole venture was a bad idea?

Find some other way to improve fuel economy without of shutting half the engine off.

Shutting off part of the engine makes perfect sense at highway cruising. All of that power is not needed to keep a truck at a constant speed on the highway. My Silverado 5.3 will get 25 mpg gallon on the highway and weighs well over 2 tons. Yet-it can pull my 5,000 pound travel trailer all day long when needed.

And again-those who have issues with the DFM are in the minority. It's not like the Tundra that's a matter of when-not if.

 

[64bawagon]

Cylinder deactivation unfortunately is here to stay for the forseeable future.


General Motors is changing its cylinder deactivation technology for next-generation V8 overhead-valve engines (expected to be the Gen VI small block) by moving the deactivation mechanism from the lifter to the rocker arm. This hydraulic "spring lock" system disengages the rocker arm from the pushrod instead of collapsing the valve lifter. [1, 2, 3]

How the New System Works
Instead of using collapsible hydraulic lifters like the current Active Fuel Management (AFM) and Dynamic Fuel Management (DFM) systems, the updated setup operates as follows: [1, 2]

• Hollow Rocker Shafts: Pressurized engine oil is routed directly through a reworked hollow rocker shaft, which acts as a primary hydraulic distribution channel. [1]
• Spring Lock Disengagement: Controlled by an oil control valve, hydraulic fluid is sent into a spring lock unit within the rocker arm. [1, 2]
• Decoupling the Valvetrain: The pressurized oil forces a pin to disengage the rocker arm from the pushrod. [1, 2]
• Valves Remain Closed: When the pushrod is decoupled, the rocker arm stops moving. The intake and exhaust valves stay closed, rendering the cylinder inactive while the piston continues to cycle. [1, 2, 3]
• Instant Reconnection: When you need immediate power, a drop in oil pressure lets the spring lock re-engage the mechanism, returning the cylinder instantly. [1]

 

[D60]

Cylinder deactivation unfortunately is here to stay for the forseeable future.


General Motors is changing its cylinder deactivation technology for next-generation V8 overhead-valve engines (expected to be the Gen VI small block) by moving the deactivation mechanism from the lifter to the rocker arm. This hydraulic "spring lock" system disengages the rocker arm from the pushrod instead of collapsing the valve lifter. [1, 2, 3]

How the New System Works
Instead of using collapsible hydraulic lifters like the current Active Fuel Management (AFM) and Dynamic Fuel Management (DFM) systems, the updated setup operates as follows: [1, 2]

• Hollow Rocker Shafts: Pressurized engine oil is routed directly through a reworked hollow rocker shaft, which acts as a primary hydraulic distribution channel. [1]
• Spring Lock Disengagement: Controlled by an oil control valve, hydraulic fluid is sent into a spring lock unit within the rocker arm. [1, 2]
• Decoupling the Valvetrain: The pressurized oil forces a pin to disengage the rocker arm from the pushrod. [1, 2]
• Valves Remain Closed: When the pushrod is decoupled, the rocker arm stops moving. The intake and exhaust valves stay closed, rendering the cylinder inactive while the piston continues to cycle. [1, 2, 3]
• Instant Reconnection: When you need immediate power, a drop in oil pressure lets the spring lock re-engage the mechanism, returning the cylinder instantly. [1]

Sign me up. If this new tech has problems I have every confidence GM will take care of me. We know this from how they've handled 6.2 problems to date

 

[64bawagon]

Youre right, trust is hard to earn and easily lost. No matter what the system I dont want it.

 

[NDL]

You guys have a much larger knowledge base than I do: why all the intricacy? Why not simply cut the fuel/spark on certain cylinders? Why deal with this at the lifter level, which has caused nothing but problems?

When did the 5.3 start with active fuel management? Did the 4.3 and 4.8's have it?

 

[clinebarger]

You guys have a much larger knowledge base than I do: why all the intricacy? Why not simply cut the fuel/spark on certain cylinders? Why deal with this at the lifter level, which has caused nothing but problems?

When did the 5.3 start with active fuel management? Did the 4.3 and 4.8's have it?

The 5.3L got AFM starting in 2007.
The 4.8L never had AFM, The Gen V 4.3L did have AFM starting in 2014

 

[mnmarlin]

My 2 cents is that if they could source decent quality lifters the system would be fine. I'm no powertrain engineer but it seems like DFM works fine, its just that the parts used are crap.

 

[MrkofXcellence]

I believe the DoD system has had reliability improvements since its 2007 introduction. I don’t believe these 6.2 failures are as a result of DoD, rather, crap parts (as mentioned above). In my 2.7 turbo (Turbo Max, if you will) it is completely imperceptible. I don’t think its nearly the scourge that it used to be. As I sit here typing I’m thinking of the current 5.3, it doesn’t have anywhere near the grenade rate as the 6.2, despite cylinder deactivation.

 

[MrkofXcellence]

“You guys have a much larger knowledge base than I do: why all the intricacy? Why not simply cut the fuel/spark on certain cylinders? Why deal with this at the lifter level, which has caused nothing but problems?”

It sounds ridiculous, but the only thing I can come up with is the “spring effect” which can be achieved when the piston is moving against closed valves. This may help to add a nominal level of MPG. I say this with a complete lack of knowledge and gross speculation.