for those of you making over 500 hp what size downpipe

[smokinHawk]

Ok im trying to find out how much power i can put out with my current DP. I have a 99 turbo trans am with a single T-76 (so its set up similar to you guys). it currently has a 2.5" dp.
i would like to go with a 3"er but its still in devolopment.
Are there any of you currently runnig over 500rwhp with a 2.5" dp?
or do you have to switch to a 3"? or bigger? i was making about 435rwhp (385 mustang dyno) on my stock engine at 5psi.
took out a head gasket so im building it up right now, lower CR putting a 224/224-114 cam in it.
i hope to push it up to at least 10-12psi and make 550rwhp. and im wondering if the DP is big enough.
im going to attack my crossover with a 2.75-2.5 around the tranny instead of in front of the engine.

just want to make some big power which = low times.
what do you guys think

 

[VictoryTrans]

I have seen and heard about alot of people going really fast with a 3" DP, really haven't heard much about a 2.5" being that quick. I do know that alot of guys are going with a 3.5" dp when the HP levels are getting really high. But with your size turbo I'm guessing a 3'' or 3.5'' would probably suit you better. In our car we're gonna be hoping to push about 800 rwhp and the 3.5" will be find. Hope this helps

 

[REDS HOT AIR]

terry houstom recomends 3.5" on anything 500 hp and up but im close to 600 at the crank and still have 2 7/8 d/p but i just got a 3" one to put on it

 

[Joe 1320]

3" minimum. If you are planning on mega high HP levels, go with the 3½". Remember that the less backpressure you have, the easier it is to push more boost though the engine. You can't really go too big after the turbo, clearance not being an issue.

 

[Reginald West]

3" downpipe 621 RWHP with tires smoking on the dyno.

 

[smokinHawk]

Yep that 2.5" DP is hurting me then. Thaks for the info.
the big problem is that the 2.5" barly fits. I know one maybe 2 guys running a 3", i dont think you can go bigger then that with out removing the stering linkage. The guy with the 3" was running 707rwhp @16psi.

WHat about your crossover, what size diameter are you guys using there?
i have a 2" but think i could get a 2.5-2.75" to work.

 

[JDD]

Red what kind of downpipe are you running?I know it's not mated to the stock elbow,right?Jim

 

[REDS HOT AIR]

its a hooker d/p with a deltagate on it. bolts to the turbo not the elbo.

 

[ijames]

If clearance at one spot is the problem and you are making your own dp anyway, I've read that crushing a round pipe into an oval as far a 10% basically doesn't hurt the flow at all. That means you could probably take a 3" pipe and oval it to 2.5 x 3.5 (or whatever it goes to in that direction) to clear the steering box, and still outflow a 2.5" pipe. Not perfect but better.

 

[Bobtempest]

Terry Houston makes a real nice 3" DP for the TTA. We have one on my son's TTA and it is a work of art. Nice fit. It also comes with a dump pipe.

 

[smokinHawk]

Do they make it for the 89 TTA or the 99 TTA ive got?

i know a 3" can fit some how just not sure how, i havent seen any, cause theres only 2 of them that i know of.

 

[Bobtempest]

Houston only makes them for the 89 TTA. Sorry I did not notice the '99.

 

[86brick]

You might want to call and talk to Rob Raymer of LS1 Motorsports www.LS1Motorsports.com cause he has a '98 single turbo ls1 Z28 that made 707rwhp/730rwtq and ran 9.94 @136.37mph.
HTH

 

[smokinHawk]

Yes i know, Ive talked to Rob a coulpe of times.
He is in the process of devoping a kit like mine, but slightly better (one with a 3" DP) BUt it will still be a while. Ill have to wait.

anyways again what size Crossover are you running?

 

[86brick]

I have an ATR 2 1/4" Crossover pipe.......

 

[zturbo]

Smokin
Why not make your own? I was about to start to make a dp for my camaro but decided to sell the kit and get a real turbo kit made up

I think a 3.5" dp can be fit into the car with some thinking and using some oval tubing on the turn down to go down by the back of the motor.

Steven

 

[smokinHawk]

Well just got a 3" from turbotech, im hoping it will give me alot of power. I just need to get it ceramic coated.
i might later look into getting a bigger one.