I Have a 2008 silverado and have HpTuners for my race project and ive been contimplating trying to mess around with it to see if i can get some better mileage. I was just curious if any of you have ever dicked around with a completely stock vehicle and saw any signifigant gaines.

And on this note what is this im seeing about gmt900 trucks being more difficult to tune than its predicessors? anyone have any insite on this?

 

Yeah the e38 pcm is kinda scary at first but you'll get the hang of it.
I'm sure you can tweak the fueling and get better MPG even being stock.

 

Mess with timing, DoD, and PE fueling can help. I saw the biggest gains from tuning my truck when it was stock by removing much of the torque management.

 

I've seen over 40hp gained with a stock tuned truck. Timing is a big factor and also these trucks come very rich from the factory.

 

Mine was in the high 10's for AFR. You can lean that out to about ~12-12.1 if you are running E10, 12.5 if pure gas. Timing will usually stop making power around 24-25 degrees on the 799/243 heads, in my experience.

I personally use a mix of a 2008 TBSS stock timing table and a 2010 Silverado timing table with 91 Octane fuel. Truck runs really good.

 

I spent allot of time tuning one of these trucks with the 799 heads and flex fuel. I couldn't get gains out of it like the older 5.3l engines, GM had it tuned pretty close already. Especially when there was e85 in the tank, with the stock tune it was running around 27* of timing.

 

My 2011 5.3 has timing about 23.5* max. Never do I see 27*. And as rich as 10.6 AFR. Surely more power can be had from a tune.