JimMueller

iTrader: (9)

I'm getting a used SLP D/D soon. Does it flow well enough to not install a cutout? Anyone have a dyno of one with both the cutout closed and open, no other changes?

LS1LT1

iTrader: (16)

I personally feel that ANY mufflered exhaust (non Loudmouth or GMMG style) will benefit from a cut out. The SLP D/D does flow well but I still think an open cut out will yield you some nice gains.

tomaSS

iTrader: (1)

Not only a small gain in top end, but will sound better IMO (if you like a loud car)

JimMueller

iTrader: (9)

Maybe when they cut off the stock catback I'll have them dyno it with an open y-pipe, then dyno it after it's installed. Depending upon the results I may put in an electric unit.

86 IROC

iTrader: (14)

Jim, my car is far less modded than yours - I consistently pick up .1 & 1 MPH open cut out vs. closed up with my dual/dual cat back. I say go for it!

Ryan02SS

iTrader: (3)

Definately go with a cutout if you want max power. The DD muffler flows remarkably well for how quiet and reserved it sounds but you will still gain power with an open cutout. The more power your making the more you will gain with a cutout versus the D/D. I can't remember the guys name on here but he picked up 13rwhp peak with an open QTEC vs D/D on his HC LS1.

Judd

iTrader: (1)

If I remember right, I only picked up something like 5 or 10hp with the cutout over my SLP DD. I will admit the placement of the cutout may have alot to do with that, it's right before the muffler {I think it's refered to as the Zed style}. It's a manual cutount and I wanted to be able to easily reach it to remove the cap. Maybe the extra distance from the Y-pipe ate up a bit of power,,,,, dunno???

I just remember being glad I welded it in myself and spending something like 25 bucks versus having a shop do it for 75 bucks.

RyanJ

Trevor from TSP had a cutout on his D/D a long time ago when he had a stock motor (bolt-on's, headers, etc.). The cutout was after the axle just before the muffler. As I remember it, he didn't gain anything at the track between open and closed. On a cam or head/cam car...i'm sure its worth something, but not so much on an SI car.