Necking down a down pipe
TECH Enthusiast
Joined: Mar 2010
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And there you have it huge dp myth debunked....I bet if you had a 4 inch catback tied into that 3.5 inch dp you wouldn't have lost anything at all. Just use straight through glass pack style mufflers or bullet style they are called.
I personally am doing 3.5 dp to a 3.5 bullet then splitting it into dual 3inch with a dynomax bullet on each tail pipe. Cant wait for the car to be quiet again.
I personally am doing 3.5 dp to a 3.5 bullet then splitting it into dual 3inch with a dynomax bullet on each tail pipe. Cant wait for the car to be quiet again.
figure the catback i removed was 30# or so which removing would make the car faster anyhow!
thats for 364ci and a pt88 at 23psi boost
i still agree 'bigger is better' but id be surprised if you could acutally measure it!
if its costing less than 10 pones may be a good compromise from a 5" downpipe out the front bumper of your 'street car'
thats for 364ci and a pt88 at 23psi boost
i still agree 'bigger is better' but id be surprised if you could acutally measure it!
if its costing less than 10 pones may be a good compromise from a 5" downpipe out the front bumper of your 'street car'
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
figure the catback i removed was 30# or so which removing would make the car faster anyhow!
thats for 364ci and a pt88 at 23psi boost
i still agree 'bigger is better' but id be surprised if you could acutally measure it!
if its costing less than 10 pones may be a good compromise from a 5" downpipe out the front bumper of your 'street car'
thats for 364ci and a pt88 at 23psi boost
i still agree 'bigger is better' but id be surprised if you could acutally measure it!
if its costing less than 10 pones may be a good compromise from a 5" downpipe out the front bumper of your 'street car'
TECH Enthusiast
Joined: Mar 2010
Posts: 519
Likes: 2
Think he's saying he was running a full 3.5 in exhaust all the way out back. Taking it off and running an open dp only made the car .10 faster. At over 1k rwhp...
TECH Enthusiast
Joined: Mar 2010
Posts: 519
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This would be a good option I would think. Cost more $ but like they say time and time again you gotta pay to play.
If you dont want to neck the dp and you do run it out front I have seen it done with a 4inch dp and it had a long dynomax bullet on it that was about 20 inchs long maybe. Could hardly hear it idle thats no lie. Sounded stock when he got on it it screamed tho which is always nice haha.
If you dont want to neck the dp and you do run it out front I have seen it done with a 4inch dp and it had a long dynomax bullet on it that was about 20 inchs long maybe. Could hardly hear it idle thats no lie. Sounded stock when he got on it it screamed tho which is always nice haha.
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Verdad Gallardo Thread Starter
Joined: Nov 2009
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From: THORNTON, PA (NEAR PHILLY)
Aftermarket k may happen at some point. I think for a 4" DP or if I want to go twins it pretty much necessary. Leaning towards a tc76 turbo which only has a 3" connection, so a 3 or 3.5" dp is all that's happening here - cant see the need to change the k out for that. I agree though that the K would free up alot of room.
here is a pass from years ago, full 3.5" exhaust (stainless works)
thats on a pt88 turbo and 24# boost
my previously posted best ever 8.49 was with a 91mm turbo, 26# boost, and no cat back. the car was also lighter from the skinnies and no cat back. you be the judge.
thats on a pt88 turbo and 24# boost
3" downpipe here only because I can't snake anything larger through the k-member without re-doing everything, and that's not happening. Yes I know it's a restriction which is why I made it as short and sweet as possible dumping out the side before the rear tire. If I had the space I would go 3.5" but no larger and if you are having backpressure problems at 3.5" something else is amiss.
800+ rwhp for reference, went 5.85 in the 1/8th last time out.
800+ rwhp for reference, went 5.85 in the 1/8th last time out.
TECH Enthusiast
Joined: Mar 2010
Posts: 519
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here is a pass from years ago, full 3.5" exhaust (stainless works)
thats on a pt88 turbo and 24# boost
my previously posted best ever 8.49 was with a 91mm turbo, 26# boost, and no cat back. the car was also lighter from the skinnies and no cat back. you be the judge.
thats on a pt88 turbo and 24# boost
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
3" downpipe here only because I can't snake anything larger through the k-member without re-doing everything, and that's not happening. Yes I know it's a restriction which is why I made it as short and sweet as possible dumping out the side before the rear tire. If I had the space I would go 3.5" but no larger and if you are having backpressure problems at 3.5" something else is amiss.
800+ rwhp for refere
nce, went 5.85 in the 1/8th last time out.
800+ rwhp for refere
nce, went 5.85 in the 1/8th last time out.
Thread Starter
Joined: Nov 2009
Posts: 1,621
Likes: 31
From: THORNTON, PA (NEAR PHILLY)
So in the end is it the HP rating that dictates the d-pipe size or the turbo's design characteristics? Obviously the hi hp guys can observe a difference, but what about the <700 whp crowd?
Really it has to do with airflow more than anything ie 600 rwhp doesn't produce as much exhaust airflow as 1000 rwhp so it's not going to have as much of an impact comparably speaking. The other thing is that the number of bends, etc also plays a big role in how it flows not just the size of the pipe. A full 3.5" exhaust that has tons of bends isn't going to flow as well as a short 3" pipe down pipe that just dumps out the side right away.