[FranknBeans]

Motor Options... what's the difference on the LS3 and L99? (besides hp, duh)

422/315 @ 5000 (LS3)*
400/299 @ 5000 (L99)*
408/553 @ 4500 (LS3)*
395/535 @ 4500 (L99)*

Sorry for the dumb questions. . .

 

[FranknBeans]

Ok, i guess the second set of numbers are the Tq. . . missed that on the info chart.

 

[Devryn]

The L99 is an "Active Displacement" engine (it runs on 4 cylinders instead of 8 when just cruising)

 

[FranknBeans]

Got ya... thanks...

any idea of the fuel savings from the L99 and the LS3?

 

[Jonz5GEN]

No fuel savings. They're rated the same mileage.

 

[FranknBeans]

thanks... so, i don't see the bennifits of getting the L99 then...

one more.. sorry.
I am guessing the L99 comes with the auto tranny and the LS3 comes with the manual?

 

[FranknBeans]

Nice magnum by the way. . . 5.7 Hemi?

I have a Srt-4

 

[Jekyll-N-Hyde]

any idea of the fuel savings from the L99 and the LS3?

No fuel savings. They're rated the same mileage.

That is a Good question ???????? if having AFM on a motor like the L99 and it doesnt give it better mileage over the LS3 which doesnt have it why even offer it ?

 

[Jonz5GEN]

thanks... so, i don't see the bennifits of getting the L99 then...

one more.. sorry.
I am guessing the L99 comes with the auto tranny and the LS3 comes with the manual?

You are correct.......and it is a very potent 5.7.


Thanks for the kudos.

 

[FranknBeans]

I'm once again 'guessing'. The fuel savings from the LS3 is suppose to come from the gear bypass (or what ever it's called). Skipping from 1st to 4th.

 

[Jonz5GEN]

That is a Good question ???????? if having AFM on a motor like the L99 and it doesnt give it better mileage over the LS3 which doesnt have it why even offer it ?

Here's how it breaks down:

LS3 rated at 422 hp coupled with M6 (stronger motor and more efficient drivetrain utilizing skip-shift)

L99 rated at 400 hp with A6 (less powerful motor and AFM to compensate for the extra drivetain power loss)

 

[Jekyll-N-Hyde]

but the purpose of the AFM is to give it better fuel Mileage correct ?

if it doesnt give it any better overall but takes HP why even offer it and just put the LS3 in it and call it Finished !

I know its a LS3 but its a L99 since it has AFM.

 

[CUONCRS]

Most of the time manuals get slightly better fuel efficiency, but the skip shift really helps that out. So the AFM basically cancels out the manual tranny's efficiency.

 

[OctaneZ28]

There is a definite fuel savings with AFM.
Anytime 4 cylinders are de-activated you're gonna save gas.
Alot depends on driving habits too... alot of city driving won't net much gain since you're not off the throttle much.

 

[Jonz5GEN]

There is a definite fuel savings with AFM.
Anytime 4 cylinders are de-activated you're gonna save gas.
Alot depends on driving habits too... alot of city driving won't net much gain since you're not off the throttle much.

Very true. The engine load and RPM are what determine when the AFM will activate or deactivate.....highway driving will net the most notable mileage increases. City driving will put the mileage well below the LS3 M6 cars.

 

[justgreat]

That is a Good question ???????? if having AFM on a motor like the L99 and it doesnt give it better mileage over the LS3 which doesnt have it why even offer it ?

the reason that the afm doesn't reflect greater fuel economy in the epa numbers is due to the test cycle of the epa and the design of afm. afm only comes into play on long extended hiway trips, something that the epa test cycles would not reflect.

my biggest gripe with the afm is the fact that the biggest drain on economy for a large displacement v8 is the intown driving, not the hiway cruising. the afm does not activate in idling conditions where you need it the most, especially with such a large motor. i would put up with some roughness in the idle if i could cut fuel delivery to half the cylinders; that would make a huge difference in the intown fuel economy.


jackg
06 sts6

 

[drc]

It would make it a lot more appealing if they could activate it for city driving. Does Chev's sytem work good or is it too early to tell?

 

[Devryn]

I think there are probably reasons for it not being for city driving. This is just me spitballing, but since most people do 90%+ of their driving in the city, it would SERIOUSLY effect engine reliability to run on 4 cylinders most of the time in the harshest conditions for driving. Unless they figured out a way to choose different cylinders regularly for the 4 cylinder driving, then you would have 4 cylinders that would get all of the wear/carbon deposits/etc. I can't imagine that's good for engine balance.

 

[OctaneZ28]

It would make it a lot more appealing if they could activate it for city driving. Does Chev's sytem work good or is it too early to tell?

Yes it does, it's very seamless, you probably won't ever notice it activating or deactivating.

In city driving, it will activate, but rarely just because of city driving habits.