Why does 6.2 seem to have more AFM lifter failures than 5.3?

[lt1gmc]

Since the 6.2 uses the same lifters and afm system that the 5.3 uses, I believe I know why the 6.2 seems to fail more often. Since the 6.2 has a good bit more power, it most likely uses the V4 mode more often than the 5.3 and thus the lifters are cycled thru on/off more often resulting in more wear in the same amount of miles. Any thoughts?

 

[Marky Dissod]

Since the 6.2L uses the same lifters and afm system that the 5.3L uses,
I believe I know why the 6.2L seems to fail more often.

Since the 6.2L has a good bit more power, it most likely uses the V4 mode more often than the 5.3L,
and thus the lifters are cycled thru on/off more often resulting in more wear in the same amount of miles.
Any thoughts?

No thoughts, the above is absolutely correct.
I'll paraphrase it to make it even more obvious to anyone who doubts what you wrote though.

When a 5.3L V8 goes Engine Half@$$, it's a 2.66L V4.
When a 6.2L V8 goes Engine Half@$$, it's a 3.1L V4.
Since the 3.1L V4 has more power than the 2.66L V4,
most 6.2L V8s will spend more time Half@$$ing compared to 5.3L.

(Should also be obvious why some Gen4 4.8L V8s did not even bother with 2.4L V4 mode.)

 

[Scarey]

Don’t forget DFM shuts down multiple cylinder configurations, even less than v4.

 

[Marky Dissod]

Don’t forget DFM shuts down multiple cylinder configurations, even more than V4.

It'd be interesting to know more about the finer details of how 'Engine Confusion' / Dynamic Fuel Management / SkipFire works, but my MEAGER understanding is as follows:
Since DFM can give any cylinder a 'break' from combustion, it follows that
(for example) DFM's V4 mode will NOT shut off the same (4) cylinders twice in a row,
unlike AFM, which (is only ever able to) always shut off the same 4 cylinders.
This can be extrapolated to DFM's other modes; constantly varying the lazy cylinder(s).

It's still the case that a 6.2L V8 with DFM will spend more time
with more cylinders deactivated compared to a 5.3L;
I.E., when a 6.2L V8 with DFM may be in V4 mode,
a 5.3L with DFM will more likely be in V6 mode (for example).
Thus a DFM 6.2L will spend more time in DFM modes
than a DFM 5.3L driven similarly.
Still continue to recommend turning off / physically deleting Cylinder (Valve) Deactivation
under 230F.

 

[dwkehoss]

No thoughts, the above is absolutely correct.
I'll paraphrase it to make it even more obvious to anyone who doubts what you wrote though.

When a 5.3L V8 goes Engine Half@$$, it's a 2.66L V4.
When a 6.2L V8 goes Engine Half@$$, it's a 3.1L V4.
Since the 3.1L V4 has more power than the 2.66L V4,
most 6.2L V8s will spend more time Half@$$ing compared to 5.3L.

(Should also be obvious why some Gen4 4.8L V8s did not even bother with 2.4L V4 mode.)

I bypassed the system in my 16 Tahoe and 19 Silverado 5.3's with Range OBD modules a few mths ago.

 

[RET423]

More failure points always equals more failures, this is true of everything

A valve train in a V-8 pushrod type engine is a very reliable design, short chain, 2 gears, simple lifter lubrication, simple leaverage pushrod/rocker assembly

Add lifters designed to collapse on demand, gears designed to alter cam timing on demand, additional duties for the oil beyond lubrication to control the new variables & light weight oil in an attempt to limit parasitic power loss & you have introduced many new failure points with little or no value added for anyone but the brain dead at the EPA

It can't be as reliable, the laws of probability & possibility & physics are brutal mistresses; the more failure points you create the more failures you get

 

[Jetskier77]

More failure points always equals more failures, this is true of everything

A valve train in a V-8 pushrod type engine is a very reliable design, short chain, 2 gears, simple lifter lubrication, simple leaverage pushrod/rocker assembly

Add lifters designed to collapse on demand, gears designed to alter cam timing on demand, additional duties for the oil beyond lubrication to control the new variables & light weight oil in an attempt to limit parasitic power loss & you have introduced many new failure points with little or no value added for anyone but the brain dead at the EPA

It can't be as reliable, the laws of probability & possibility & physics are brutal mistresses; the more failure points you create the more failures you get

Very well stated.

 

[Marky Dissod]

More failure points always equals more failures, this is true of everything.
A pushrod V8 valvetrain is a very reliable design, short chain, 2 gears, simple lifter lubrication, simple leverage pushrod / rocker assembly.

Add lifters designed to collapse on demand, gears designed to alter cam timing on demand,
additional duties for the oil beyond lubrication to control the new variables, & light weight oil in an attempt to limit parasitic power loss,
& you have introduced many new failure points with little or no value added for anyone but the brain dead at the EPA.

It can't be as reliable, the laws of probability & possibility & physics are brutal mistresses; the more failure points you create the more failures you get.

And the 6.2L will 'cross' those extra failure points with greater frequency than a 5.3L.

The more often you roll dice, the more likely that you will sooner or later roll 'snake eyes'.

 

[vcode]

It'd be interesting to know more about the finer details of how 'Engine Confusion' / Dynamic Fuel Management / SkipFire works, but my MEAGER understanding is as follows:
Since DFM can give any cylinder a 'break' from combustion, it follows that
(for example) DFM's V4 mode will NOT shut off the same (4) cylinders twice in a row,
unlike AFM, which (is only ever able to) always shut off the same 4 cylinders.
This can be extrapolated to DFM's other modes; constantly varying the lazy cylinder(s).

It's still the case that a 6.2L V8 with DFM will spend more time
with more cylinders deactivated compared to a 5.3L;
I.E., when a 6.2L V8 with DFM may be in V4 mode,
a 5.3L with DFM will more likely be in V6 mode (for example).
Thus a DFM 6.2L will spend more time in DFM modes
than a DFM 5.3L driven similarly.
Still continue to recommend turning off / physically deleting Cylinder (Valve) Deactivation
under 230F.

I'd like to see the algorithm on how the DFM works. Cylinder deactivation only takes place under light loads, far below the maximum HP ratings of the engines. The horsepower required to move these trucks at 55 mph is the same no matter what engine is being used. So if 2 trucks are driven in the same manner, would there really be much of a difference?

 

[Marky Dissod]

I'd like to see the algorithm on how the DFM works.
Cylinder deactivation only takes place under light loads, far below the maximum HP ratings of the engines.
The horsepower required to move these trucks at 55 mph is the same no matter what engine is being used.

So if 2 trucks are driven in the same manner, would there really be much of a difference?

The 6.2L V8 will spend more time DFM'ing more of its cylinders more often, vs an identically driven 5.3L V8.

 

[lt1gmc]

Don’t forget DFM shuts down multiple cylinder configurations, even less than v4.

DFM is not on this generation of trucks, these trucks are only V8 or V4.