like said above. one run doesn't mean much. i have ran back to back open and closed on several set ups. some na, some nitrous, some boosted. sometimes on the street with a gtech, sometimes at the track, sometimes at the dyno. i always picked up with open exhaust. picked up a little down low and more up top. typical in the 1/4mile NA was .1-.2 drop in et.

here is a dyno from a few years back. i can't remember the exact details but the chart and notes on the chart pretty much tell the story. i have charts that show 60rwhp by opening up the cut out but that was on a boosted set up.

 

That's exactly consistent with my butt-o-meter. Is that a 5.3 or 6.0?

 

pretty sure it was a stock 6.0

 

mine put 267/296 in 2nd gear with 89 tune.

 

I dont know about that. My 4.8 likes it open. I usually run .2 faster with it open, and that is with a loudmouth I series muffler and dual exhaust so there isnt much restriction in the first place.

 

I could see how it would lose some down low with it open, I bet that it would help at the top end of the track though.

 

I lose some low end power with mine open, but it seems to pull harder after about 40 MPH.

 

that chart above starts at 2500rpm and there is allready a slight gain. maybe if your running a stock converter you could loose a little down really low?

 

well personally i was doing 477 rwhp with the cut out close.then we decided to open it and it went down from a 477 to 470.i could fell it alittle weaker in top end .mine was a 6.0.guess my truck didnt like open exhaust. i lost 7 rwhp in the dyno

 

i would bet money that there was another factor in that test.

it could be a little lean on the closed run and then more lean to the point of loosing power when open.

if you were spraying might be lower bottle presure on the open run.