Pipe sizing for turbo setup???

mikec · 10-17-2001, 04:25 PM

Hi all, Just wondering what your thoughts are on pipe sizing for various parts of a turbo system. What's a tipical dia. size for headers? IC piping ( compressor to IC)? Up-pipe? Down-pipe? Exhaust?
Pardon the ignorance....Any info would be greatly appreciated....I have read up on it quite a bit but find myself more confused than ever... Thanks for the help.

Mike.

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Soon2Bgreat · 10-17-2001, 04:36 PM

If you're just going to run 5-8 or 9 psi. a 2.5' turbo back exhaust with hi flow cat will flow just fine. A 3' turbo back might be a little nicer, but not needed, and probably not much difference. You can leave the uppipe stock, it is no big deal, unless you plan on going more hardcore. Same thing with headers. they are perfectly fine even for higher applications, they are robust, and flow fine.

mikec · 10-17-2001, 05:49 PM

Thanks for the quick reply. I hadn't mentioned that my car is a MY00 Impreza L wagon, and that the headers are single pipe instead of dual pipes like the RS. I don't know how much of a difference this makes, but they seem awfully small... As for IC piping, I read somewhere that you can run into problems if you go too big. Any idea how big "too big" is?
Thanks again.
Mike.

subachad · 10-17-2001, 06:13 PM

The outlet flange on your 2.2 will be the same as the RS and the 1.8L. For the up pipe, it's best to keep it at 2" as to maintain exhaust velocity. If you need an up pipe made, pm me and I'll make one for you.

As for the downpipe, there's a few schools of thought on this. One is you want to maintain the velocity to create a vacum coming out of the turbo so an open or 3" dump right off the turbo will kill your torque. This is kinda what I have right now while I try to get the time to finish completing the exhaust. I actually went back to my old "midas" special exhaust which is only 2.25" and all crush bends, but gained some power over the 3" dump, it's also much quieter. You need the exhaust big to break up the swirl and keep backpressure off the turbo all while maintaining the exhaust velocity.

My intercooler is 2.25" and the old setup was before the intercooler was installed was 2".

Chad
93 1.8T

10-17-2001, 04:25 PM	#1
mikec Scooby Newbie Member#: 7551 Join Date: Jun 2001 Location: Calgary,Alberta	Pipe sizing for turbo setup??? Hi all, Just wondering what your thoughts are on pipe sizing for various parts of a turbo system. What's a tipical dia. size for headers? IC piping ( compressor to IC)? Up-pipe? Down-pipe? Exhaust? Pardon the ignorance....Any info would be greatly appreciated....I have read up on it quite a bit but find myself more confused than ever... Thanks for the help. Mike. * Registered users of the site do not see these ads.

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10-17-2001, 04:36 PM	#2
Soon2Bgreat Scooby Specialist Member#: 2258 Join Date: Sep 2000 Chapter/Region: Tri-State Location: Irvington, New York, USA Vehicle: 1999 gc8 ver7 6mt GT35R 504.7whp;)	If you're just going to run 5-8 or 9 psi. a 2.5' turbo back exhaust with hi flow cat will flow just fine. A 3' turbo back might be a little nicer, but not needed, and probably not much difference. You can leave the uppipe stock, it is no big deal, unless you plan on going more hardcore. Same thing with headers. they are perfectly fine even for higher applications, they are robust, and flow fine.

10-17-2001, 05:49 PM	#3
mikec Scooby Newbie Member#: 7551 Join Date: Jun 2001 Location: Calgary,Alberta	Thanks for the quick reply. I hadn't mentioned that my car is a MY00 Impreza L wagon, and that the headers are single pipe instead of dual pipes like the RS. I don't know how much of a difference this makes, but they seem awfully small... As for IC piping, I read somewhere that you can run into problems if you go too big. Any idea how big "too big" is? Thanks again. Mike.

10-17-2001, 06:13 PM	#4
subachad Scooby Specialist Member#: 8488 Join Date: Jul 2001 Location: Sin City Vehicle: 1993 Impreza GCStyle Teal	The outlet flange on your 2.2 will be the same as the RS and the 1.8L. For the up pipe, it's best to keep it at 2" as to maintain exhaust velocity. If you need an up pipe made, pm me and I'll make one for you. As for the downpipe, there's a few schools of thought on this. One is you want to maintain the velocity to create a vacum coming out of the turbo so an open or 3" dump right off the turbo will kill your torque. This is kinda what I have right now while I try to get the time to finish completing the exhaust. I actually went back to my old "midas" special exhaust which is only 2.25" and all crush bends, but gained some power over the 3" dump, it's also much quieter. You need the exhaust big to break up the swirl and keep backpressure off the turbo all while maintaining the exhaust velocity. My intercooler is 2.25" and the old setup was before the intercooler was installed was 2". Chad 93 1.8T