The engine option for the upcoming 2009 GXP version of the G8 has been confirmed, sort of. GM has uploaded the engine designation LS3 into the database for the GXP. LS1TECH - View Single Post - GXP model and manual transmission confirmed for 2009. In Corvette trim (only 2008 vehicle with this engine) the .2 liter increase over the 400hp LS2 is good for a whopping 430hp and 424 lb-ft of torque. Whether the engine is transplanted complete, or is ultimately detuned it will still be quite a power increase from the G8GT's 361hp.
The GXP is reportedly also the only model of G8 that will be available with the Tremec manual 6-speed. As of this writing the GXP is expected to also be available with the 6-speed Hydramatic from the GT.
We have seen 18RWHP gains on an LS1 motor just by re-flashing the ECU with a new tune. It would be reasonable to assume that you could get at least 30RWHP out of the L76 just by retuning the ECU. You would definitely see more torque because GM is notorious for Torque management and we turn that off on everyone one of our tunes…
Last edited by RPM Motorsports; 03-12-2008 at 06:40 PM.
LS3 will be, pending SAE certification, 402 hp, 402 lb-ft torque in teh GXP, down from th e'vette's 430/424 but that should also mean minimal reductions in mpg. O-60 in 4.7 and 13.0 flat for the 440 (1/4 mile)