Motor Information

Curious as to why the General didn't use the 400hp version from the GTO in the G8?

wesj1 said:

Curious as to why the General didn't use the 400hp version from the GTO in the G8?

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Mostly emissions and mpg, and the fact that the LS2 is out of production for domestic car service. You can find a LS2 with 390 hp in a Trailblazer or Saab 9-7, and several instances of a VVT edition of the L76, but in cars, the G8 is the only North American GM product with 6.0l displacement, and is largest outside of Corvette. The L76 in the G8 is the only L76 with AFM (active fuel management) designed to power down 2 or 4 cylinders under low load to return higher mpg. The hope also is that however the engine is configured when the manual arrives, that the dreaded Gas Guzzler Tax will not appear on your window sticker. ON that note, right now it is rumored/stated/assumed that the L76 with Tremec 6-speed will not have AFM.

40+ Extra HP ...

I've heard rumors of the tune that's supposed to allow the horsepower in the G8 GT to increase by 40+ ... running on premium fuel since it's rated at 361 hp using 87 octane. Anyone know of how this is accomplished. I'm new to tuning. And how would this affect gas mileage when NOT in WOT.

I am new to the world of tuning N/A vehicles, but in the world of forced induction, you can tune to get gobs of power out of those little engines. But the basics are go to be roughly the same (correct me if I am wrong, as I want to learn). You can start tweaking the engine management in the ECU to adjust fuel ratios, trims, and the like. That engine would have to be choked down quite a bit to get 40 hp out of it by just opening up the ECU. I would imagine that you would have to do some intake work and ECU tuning to get those 40 horses. I have read guys throwing around the 30hp gain number, but it is just hard to say with a car that tuners have yet to get a hold of. It is going to be exciting to see the tuning of the GXP.

Stingpac said:

And how would this affect gas mileage when NOT in WOT.

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Oh, almost forgot. Tunes can actually get you more MPGs. It is all how you use the noisy pedal. I have found that in my old WRX, that I had an off the shelf tune on, I had about 20 more horses and I could use them for good and squeeze a mpg or 2 out here and there, but having the power available, and not using it, seemed like such a waste. HAHA!

Thanks for the reply awd4life. I actually got lucky and picked up one of the Black G8 GT 888 Series about 4 days ago. The power is great, but I might as well make the most of the engine, especially if it's supposedly an inexpensive upgrade. I'm gonna go to one of the performance shops and ask about the intakes and/or an ECU tune. I have a feeling a CAI would do alot for the car since there is NO engine sound to it. Stock, it sounds like an altima or somethin' haha.

There are already at least 3 or 4 tunes for the G8, with dyno runs to back up the 30-40 hp gains. Plus they are reporting mpg gains. Sounds contrary, more hp, less gas, but if the factory tune is too rich it is wasting gas to start with. Someone ran the numbers on a 3 mpg jump tuning to 93 instead of 87 and the cost per mile will repay the cost of the tune all by itself - hp is the freebie.

It's my understanding (subject to verification) that the G8, although designed to run on any gas, was SAE certified on premium. I know the EPA tests were.

EM and letting your engine breathe better (intake and exhaust) is the "easiest" way to get power out of a N/A engine. Smoother piping will allow gases to flow less turbulently and thusly get into the engine easier.

More hp means that the engine is producing more power on the same amount (depending on the tune) and that means that the engine doesnt have to work as hard to do the same work.

Chief Pontiac ... that's great news .. .where can I read more specifics about those G8 tunes and where ta get them... 'cause I'm pretty much ready ta make that happen... ESPecially if it's gonna increase the gas mileage ... sounds like a win/win situation. Or should I just go to a local auto performance shop and further inquire?

AWD4LIfe ... The intake and exhaust sounds like a good idea .. I might just stick with the CAI ... 'cause I don't wanna be too loud ... settin' off car alarms everytime I start the car lol.