Is AFM disabled when using paddle-shifters?

[nester7929]

I know that the auto L99 uses AFM, but is it disabled when in step-shift mode?

[CamaroSpike23]

the only times afm are active are during idle and highway cruising when there isnt a large load on the motor (and thats only for 8 minutes at a time). so if you downshift, or punch the gas, it will shut off and reactivate the other 4 cyls

[Emher]

^AFM is only on 8 minutes at a time? Hah! My manual fuel saving is on all the time!

[Croathlete]

It's actually cycles 10 min in V4 and 1 min in V8.

"If all enabling conditions are met and maintained for DoD operation, the ECM calibrations will limit cylinder deactivation to a cycle time of 10 minutes in V4 mode, and then return to V8 mode for 1 minute."

And I would like to think that an automatic in V4 mode would save more gas than a manual V8...

[Emher]

It's the "all enabling conditions" that kills it methinks. You'd need to have a straight road with no hills that would make the engine switch to V8 mode. And I'm not entirely sure it actually save that much gas. My 4 cylinder gets at most 26 mpg, my dad claims he's gotten it up to 30 mpg. And several drivers of the 4th gen on this board has claimed that they get 30 mpg with ease, so the difference is...? And right me if I'm wrong, but an engine that has more power at low revs, say an LS3, would logically give at least a good a fuel economy as a turbo 4 that has to build up a bit to the power?

[jmliptak]

Originally Posted by Emher

It's the "all enabling conditions" that kills it methinks. You'd need to have a straight road with no hills that would make the engine switch to V8 mode. And I'm not entirely sure it actually save that much gas. My 4 cylinder gets at most 26 mpg, my dad claims he's gotten it up to 30 mpg. And several drivers of the 4th gen on this board has claimed that they get 30 mpg with ease, so the difference is...? And right me if I'm wrong, but an engine that has more power at low revs, say an LS3, would logically give at least a good a fuel economy as a turbo 4 that has to build up a bit to the power?

More friction with more cylinders and the individual pistons and all the goodies they attach too are generally heavier and larger, so it takes more energy to move them, but I am not an engine expert. I am sure there is someone on here who can give a better explanation. The AFM is generally only good for a few MPG anyway, which was your original point.

[Emher]

^Yes thank you for making it a bit clearer, lol. Yeah my point is the AFM only helps a bit, it's still can't change the fact that the car have a certain weight, aerydnamic drag and that the engine is basically a V8.

[Angrybird 12]

Having driven my son's Silverado a few times and watched the AFM system working I know for a fact that
AFM engages only when you are in top gear and either holding a constant throttle position on have your foot off the throttle.
Anytime you are "Giving it gas" to either hold a constant speed even on the slightest incline or trying to accellerate the AFM will Disengage and you will be running on all cylindars.
In my opinion if you live it flat country you will actually see AFM help, but living in the mountians like I do or even in city driving it will not have very much effect on your MPG.

[jmliptak]

Originally Posted by Emher

^Yes thank you for making it a bit clearer, lol. Yeah my point is the AFM only helps a bit, it's still can't change the fact that the car have a certain weight, aerydnamic drag and that the engine is basically a V8.

:seesaw:

[CamaroSpike23]

Originally Posted by Emher

^AFM is only on 8 minutes at a time? Hah! My manual fuel saving is on all the time!

so you drive in 6th all the time?

lol



its for roughly 8 minutes then it fires the 4 cyls back up for 1 minute to rewarm the cyls and flow the oil and whatnot.

[Mr Twisty]

31mpg hwy testing on a Caddy sedan deville at 55mph, light hills. AFM works.

[Croathlete]

Originally Posted by MisterCamaro69

31mpg hwy testing on a Caddy sedan deville at 55mph, light hills. AFM works.

28 miles of my 33 mile commute are highway miles. I'm expecting AFM to be engaged for most of it (with no traffic of course). If I could pull out 30 MPG while AFM is engaged, I would be extremely happy.

[theholycow]

Originally Posted by Emher

an engine that has more power at low revs, say an LS3, would logically give at least a good a fuel economy as a turbo 4 that has to build up a bit to the power?

Given really tall gears, the big engine could get close.

Originally Posted by jmliptak

More friction with more cylinders and the individual pistons and all the goodies they attach too are generally heavier and larger, so it takes more energy to move them, but I am not an engine expert.

Nor am I, but I do know that engine friction goes up as a square of RPM...making a high-revving smaller engine lose lots of its advantage when the big engine turns a really tall gear.

[camaro1]

the problem is when you want to add a little power to your L99 auto car,, you want to do a camshaft swap but you cant because the special lifters used with the AFM will only tolerate so much lift and valve spring pressure and limited rpm

you can swap in standard LS2/LS3 lifters and eliminate the afm system as long as the tuner people come out with a tuner program to remove the trouble codes for the AFM/DOD system