How Much Am I Leaving On The Table?!
Thread Starter
Joined: Sep 2004
Posts: 2,013
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From: Hicksville MN!
How Much Am I Leaving On The Table?! I have an LS7 427 in an F-Body(see signature for setup)and I am running a kind've goofy exhaust setup.Right now I'm running 1 7/8 Kooks Headers through an off road ory (cats delete)which dumps into a 2.5 inch pipe back to the 3 inch cutout which is positioned where the common spot is by the back seat.Then from here it goes through my stock WS6 exhaust.My question is how much am I leaving on the table if any?I was told by a certain tunner to get either dual cutouts in the y pipe somewhere, or put a 5 inch pipe after the y to the cutout.What do you guys all think?I was told it is all corked up since my engine flows so much air and I'm not getting it back out.
Traver
Traver the 2.5 single pipe is likely holding you back a lot...with that much money wrapped up in your engine why skimp on the exhaust?
If you want to stay single I would run a full 3.5" or 4" exhaust all the way around...3.5" y-pipe into a 3.5" Intermediate, through your choice of 3.5 mufflers and tailpipe. If not, do 3" duals.
If you want to stay single I would run a full 3.5" or 4" exhaust all the way around...3.5" y-pipe into a 3.5" Intermediate, through your choice of 3.5 mufflers and tailpipe. If not, do 3" duals.
Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
Sounds about right but wouldn't putting dual 3 inch cutouts in up by the y-pipe serve the same purpose?I know I should have at least 18 inches of pipe after the headers,or is this a mythe?So many differances of opinions so I'm trying to get some real good answers from some credible people who have tried or experimented with exhaust options.Traver
i would say cutouts in the Y would be fine, and the 18 inch thing may have to do with compensating for lack of collector tuning more than anything else. The only problem I would have with that is cutouts are notoriously PITA's, leaking and rusting and whatever. I prefer to just build the exhaust right and not have to worry about it 
My estimate would be that you are losing ~ 40RWHP.
I have a 375ci iron block with L92/L76 setup and a 647/640 23x/24x cam. I had a 1-3/4 Grotyohann setup into a single 3" bullet. By just sectioning my ypipe into a flowmaster merge collector dual 3" in and single 4" out and adding a new 4" bullet I gained 20 rwhp.
I have a 375ci iron block with L92/L76 setup and a 647/640 23x/24x cam. I had a 1-3/4 Grotyohann setup into a single 3" bullet. By just sectioning my ypipe into a flowmaster merge collector dual 3" in and single 4" out and adding a new 4" bullet I gained 20 rwhp.
you do not have to have 18 inches of pipe after the headers, I'm runnign turndowns off teh end of teh header collector and it's fine like that, the added pipe os for the o2 sensors, which you probably dont' have any of them workign anyway if the car is tuned in open loop which I would expect with a setup like yours.
If you want to leave a full exhaust on, have a Y pipe made and use a good merge collector before the I pipe, and I'd run 4 inch the whole way. Or, run a 3 inch true dual setup.
If you want to leave a full exhaust on, have a Y pipe made and use a good merge collector before the I pipe, and I'd run 4 inch the whole way. Or, run a 3 inch true dual setup.
Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
Thanks for all the responses guys!We took the Y-Pipe off today and slid 2 12 inch straight pipes right off the header collectors and.........WOW!I gained 15 rwhp/22 rwt right off the bat!It's not quite 40 horse but it's alot,probably worth a couple 10ths at the track?My MPH was quite low for my times and I'm thinking this was the culprit.Now I have to figure out what to do.I wonder if dual cutouts at the headers will work or not?Not much room under these F-Bodies!!Traver
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FWIW, even on my LS1, I noticed a big gain in torque when I switched to the TSP td's. I have the 3" tubing with an x pipe. Car accelerates much better from a stop now. With an engine that big, I personally would get some TD's on there
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Verdad Gallardo Thread Starter
Joined: Sep 2004
Posts: 2,013
Likes: 85
From: Hicksville MN!
I know what you mean about the true duals.My question is will they fit without banging on everything under there.......and who around here can even do a decent mandral bent true dual setup?Not too many good exhaust shops around here!Traver