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I've recently started putting together intake kits for the W-Body platform and its different engines. On the LS4 ASI, I include a larger MAF sensor that's 1/2" larger than the factory unit, plugs into the factory connector and is very cost effective.
Why the MAF upgrade? The LS4 uses the same MAF as the Series III 3800, the Impala/Monte 3500 and 3900 V6s and other Gm V6s. Note: all V6s. The LS4 airbox is infact the same as the 3500/3900 Impala/Monte. GM simply reused these components they deemed acceptable for a 5.3 V8.
Initial testing showed a 1 KPA reduction in intake manifold vacuum at full throttle, meaning the MAP sensor values were 1 KPA closer to atmospheric pressure at WOT, meaning less restriction in the intake before the intake manifold. Worth dyno testing to verify, so I did.
Results: 6-7 wheel horsepower gain when switching from an existing aftermarket intake to the Overkill MAF upgrade kit. This is on a bolt-on equipped 08 GXP with exhaust work only to compliment the intake and tuning. Stock intake manifold with the neck pinch, stock throttle body, all the reasons someone might say its not worth doing a MAF upgrade shows otherwise.
Once again, these gains are Overkill MAF upgrade intake vs another aftermarket intake, and both intakes were Overkill tuned. Gains would be higher compared to stock airbox and tune.
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Best of all: This ASI kit is available on my website for less than the cost of typical aftermarket LS4 intakes. Not only do you get a full intake kit with a brand new GM MAF sensor upgrade, but you get it for less than the cosmetic intake kits on the market which reuse the small factory MAF currently on your vehicle.
http://www.getoverkilled.ca/ls4parts.html
My thanks to Nathan for the use of his GXP for the dyno testing, he got a free ASI kit for his time.
