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Will the L99 have the ability to switch it to a constant 8 cylinder mode? If not, what happens when you do a hole shot? Is there any hessitation when going from 4 to 8 cylinder mode?
 

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Just ask anyone who has an LS4 Monte, Impala, GCP of Lacross Super. There is no hesitation. I've had a LS4 Monte Carlo for almost 3 years, and I don't feel a hesitation under most circumstatnces. The only time I do is if I'm messing with the throttle on/off.
 

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Howard, it is possible to turn it all the way off? Wow, I was not aware of that. That's cool.

Personally I would like to turn it UP a bit.
Supposedly you can turn it up from 5% to 11% (meaning % of engine load needed for AFM to disengage) and gain 2-3MPG.
And supposedly this can be done in conjunction with a looking-for-more-horsepower tune.

I don't know these things to be fact, but going off what I've heard......
 

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AFM is completely adjustable. It is based upon engine rpm, manifold pressure and gear. We have played it with a bit on the trucks but its kind of querky.

There is a paramater to turn it completely off.

Howard
 

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For those asking about detecting the switch between 4 cylinders and 8 cylinders, it becomes more apparent with aftermarket exhaust through a noticeable change in tone. When cam/heads are added to the equation, it becomes easier to tell through slight 'surges' when applying more throttle at cruising speed, depending on throttle position and engine load.

AFM will not function (or I should say intervene) when in WOT or when in Manual Tap-Shift mode.
 

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Great insight.

Thanks!

5thgen.org; killing the Haters since 2002!
 

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Is there any way you could manually engage the AFM, and just turn it on or off at will. I know this sounds cumbersome, but it would be neat if someone was on a road trip and wanted to make sure it was on all the time to conserve fuel.

Also, does AFM kick in during idling at lights, idling out of a driveway or just plain driving <10% throttle. Can the car accelerate without having to be in V8 mode, or must it be cruising for AFM to engage?


Thanks!!
 

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Is there any way you could manually engage the AFM, and just turn it on or off at will. I know this sounds cumbersome, but it would be neat if someone was on a road trip and wanted to make sure it was on all the time to conserve fuel.

Also, does AFM kick in during idling at lights, idling out of a driveway or just plain driving <10% throttle. Can the car accelerate without having to be in V8 mode, or must it be cruising for AFM to engage?


Thanks!!

no, it does not kick in while idling. sure you can accelerate as long as you are still under the %throttle.


An LS3 and L99 are not only different because of AFM, but also VVT. AFM requires different lifters and oil passages, higher pressure oil pump and VVT has special cam gears/front cover, etc...
 

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LS3 does not.
 

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AFM is completely adjustable. It is based upon engine rpm, manifold pressure and gear. We have played it with a bit on the trucks but its kind of querky.

There is a paramater to turn it completely off.

Howard
What I would like is the ability to turn it off and on. I like the idea of it for most driving, but I certainly don't want it on if I'm at the track (not the strip).
 

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Its a non issue. The only time AFM would kick in is when you are cruising with very little throttle opening. It doesn't come on at idle and if you are launching it you go from idle (not on) to a significant throttle opening (not on) so it doesn't matter what the transition is like because it would never have been activated. If you do a lot more city stop and go driving than highway driving chances are it will almost never be on.
 

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We have spent over a year now fiddling with our G8 (L76 engine, virtually identical to the L99).

AFM is very picky. GM has spent a fortune in development of this system. I spoke with a well respected engineer behind the AFM/DOD systems and in response to my question of altering the system he says " If you think your gona beat us on this one you've got another thing coming".

We have made over 600rwhp on a stock long block L76 through a 6l80e with the AFM on.

Our policy about the AFM is either to have it on or off.

For those of you wondering if its possible to have some sort of switch. The answer is yes. But the switch would only be activating or deactivating within the parameters which GM has pre programmed.

Thanks
Mike Haddad
 

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We have spent over a year now fiddling with our G8 (L76 engine, virtually identical to the L99).

AFM is very picky. GM has spent a fortune in development of this system. I spoke with a well respected engineer behind the AFM/DOD systems and in response to my question of altering the system he says " If you think your gona beat us on this one you've got another thing coming".

We have made over 600rwhp on a stock long block L76 through a 6l80e with the AFM on.

Our policy about the AFM is either to have it on or off.

For those of you wondering if its possible to have some sort of switch. The answer is yes. But the switch would only be activating or deactivating within the parameters which GM has pre programmed.

Thanks
Mike Haddad
Thank you, Mike!

:5go:
 
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