Thread: LS3 vs L99?
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Old 02-11-2009, 01:54 PM   #3
PatrickfromMD's Avatar
Drives: Navigator/Corvette/2010 Camaro
Join Date: Aug 2008
Location: Maryland
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Originally Posted by SGOS252382 View Post
According to GM High Tech some of the major difference between the two motors are
1. VVT
2. AFM
3. 10.4:1 Compression ratio
4. lower lift cam

But one thing that really caught my eye was the lower fuel cut off rpm for the L99. GM High Tech Mag states that the fuel cut off for the LS3 is 6600 rpms, while the fuel cut off for the L99 is 6200 rpms. Is this really the fuel cut off for the L99? That seems too low.
If this is true then red line must be somewhere around 6000 rpms for the L99 vs 6500 rpms or so for the LS3. I'm wonder how much this will affect the peformance of the L99 A6 vs the LS3 M6.

To compare- My LS2 GTO's redline is 6500 rpms and I'm not sure about the fuel cut off.

I have read much of the same for the L99 motor (I have one on order).
In addition to not needing as high an RPM due to less cam, I read that the AFM does impose some restrictions to the valve train at higher RPMs.
This should not be an issue if you keep the motor stock. If you are looking at adding traditional performance mods, then this RPM limit needs to be taken into consideration.
Iím keeping my ears open for ways to beef up the valvetrain to handle more, but have yet to see any useful information short of removing the AFM

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