practical downpipe limit???
Thread Starter
Launching!
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Joined: Feb 2005
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From: Chesapeake, Virginia
practical downpipe limit??? I am just about ready to order all my parts for my opel and had a question on down pipe size.
I know the consensus on down pipes is generally the bigger the better but where is the point of diminishing returns? This is a tube chassis car so I have room to work with up to 4" maybe a tad more per side. The minimum planned as of now is dual 3", but since space is available how big should I go?
This is essentially a street car and will have exhaust running at least to the rear axle.
Pics of car here https://ls1tech.com/forums/conversio...9-opel-gt.html
Combo is
402 cube LS2 9:5 compression
TU2 cam PRC 237 heads
Twin 6266 turbos
4l80 trans 9" rear
thanks in advance
I know the consensus on down pipes is generally the bigger the better but where is the point of diminishing returns? This is a tube chassis car so I have room to work with up to 4" maybe a tad more per side. The minimum planned as of now is dual 3", but since space is available how big should I go?
This is essentially a street car and will have exhaust running at least to the rear axle.
Pics of car here https://ls1tech.com/forums/conversio...9-opel-gt.html
Combo is
402 cube LS2 9:5 compression
TU2 cam PRC 237 heads
Twin 6266 turbos
4l80 trans 9" rear
thanks in advance
Last edited by SR-71 SS; Jan 7, 2013 at 10:47 PM.
I have no 1st hand experience but maybe bump it to 3.5 to go out the back. If the exhaust side is a 3" v-band you would think that would because the restriction before a 3.5" pipe. Again just speculating here.
TECH Regular
Joined: Oct 2012
Posts: 476
Likes: 2
125% of the turbines exducer is the minimum rule of thumb.
3 inch has supported 700 @ the wheel on certain combos.
With the length of run you are talking... id personally do 3.5.
I would also reconsider your cam choice if it hasnt been purchased yet.
3 inch has supported 700 @ the wheel on certain combos.
With the length of run you are talking... id personally do 3.5.
I would also reconsider your cam choice if it hasnt been purchased yet.
FormerVendor
Joined: Dec 2001
Posts: 2,444
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From: WWW.SPEEDINC.COM
We've built several single 7675 cars at 900+rwhp with a single 3in downpipe.
That being said, dual 3 inch is not going to restrict you at all. (Not ideal but we've seen 1000++rwhp with dual 2.5 systems).
If you can easily fit dual 3.5 it certainly wouldn't hurt but I don't think it would pick up any power.
Looks like a great combo (including the cam!) in my opinion.
That being said, dual 3 inch is not going to restrict you at all. (Not ideal but we've seen 1000++rwhp with dual 2.5 systems).
If you can easily fit dual 3.5 it certainly wouldn't hurt but I don't think it would pick up any power.
Looks like a great combo (including the cam!) in my opinion.
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TECH Regular
Joined: Nov 2007
Posts: 485
Likes: 1
We've built several single 7675 cars at 900+rwhp with a single 3in downpipe.
That being said, dual 3 inch is not going to restrict you at all. (Not ideal but we've seen 1000++rwhp with dual 2.5 systems).
If you can easily fit dual 3.5 it certainly wouldn't hurt but I don't think it would pick up any power.
Looks like a great combo (including the cam!) in my opinion.
That being said, dual 3 inch is not going to restrict you at all. (Not ideal but we've seen 1000++rwhp with dual 2.5 systems).
If you can easily fit dual 3.5 it certainly wouldn't hurt but I don't think it would pick up any power.
Looks like a great combo (including the cam!) in my opinion.
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Thread Starter
Launching!
iTrader: (2)
Joined: Feb 2005
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From: Chesapeake, Virginia
looks like 3.5 duals it is. I prefer to overbuild now and not have to redo later should I add more cubes or more turbo down the road. I appreciate the input from everyone who posted. I will update the build thread once parts arrive and fabrication begins. Since the knickname for the opel gt is the mini vette I think it would be kind of neat if I could run the downpipes as sidepipe exhaust like the old stringrays did.
