Forced Induction Custom FI Setup Questions

2 1/4 downpipe and 1 7/8 exhaust

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Old 03-21-2004, 03:38 PM
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Default 2 1/4 downpipe and 1 7/8 exhaust

Can this exhaust setup cause 9psi to not feel like 9psi?
My boost guage says 9psi but it just dont feel like it.
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Old 03-21-2004, 06:14 PM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

lose the 1 7/8 nonsense, get it at least 2.25... but if you get it done at an exhaust place, just get 2.5, they dont charge for pipe size.
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Old 03-21-2004, 06:35 PM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

9psi is 9psi, it could just be that you got a ---- turbo with a low cfm rating compressor wheel, exhaust should really be the diameter of the hole on the turbine side that the downpipe bolts up to
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Old 03-21-2004, 11:35 PM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

It could be that the excess backpressure is causing your turbine to spool slowly. That would make the set up reach peak boost slower and you won't get the "mashed to the seat" feeling as much with a larger exhaust.

So, yes, if you're refering to the feeling of acceleration. A larger exhaust (2.25 atleast) will cause your turbine to spool relatively faster reaching peak boost lower in the powerband and increasing acceleration.


if you want to do it on the cheap, go to a exhaust shop and ask to rummage through their bins, grab a good length of 2.25 pipe rom a truck or something, find some worn out hangers, and go buy a couple silenced glasspacks. then either have a friend weld it up for you or rent a buzz box. it'll cost you like 50 bucks if you're true ghetto.
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Old 03-22-2004, 07:11 AM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

Originally Posted by surfer
9psi is 9psi, it could just be that you got a ---- turbo with a low cfm rating compressor wheel, exhaust should really be the diameter of the hole on the turbine side that the downpipe bolts up to
Im running a TDO5H and I think it needs a rebuild but im not sure.I think im going to run a 2.5 exhuast I can weld it myself If that will do the trick.
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Old 03-22-2004, 11:20 AM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

my buddy is doing about the same setup on his 91 crx. he doesnt have the $$ right now to do a catback, so he put a test pipe on there. he felt a big improvement. it opened it up a bit.
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Old 03-22-2004, 04:03 PM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

dude if you can weld/have a welder just rig up a cheap exhaust that shoots out the side ofthe car instead of going all the way back, it'll save a ton of cash.
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Old 03-22-2004, 04:32 PM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

You can get a 2.5" ss midpipe on ebay for around $100 shipped. It's OBX, but it's not half bad for the price. It's 304 stainless mandrel bent with a built in resonator. I have one on my car now but I'm not boosting yet, so I can't vouch for how it is under boost. It's actually a little worse NA, but I expected that. It's an option and it won't break the bank.
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Old 03-24-2004, 04:11 AM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

ok I took my complete turbo and mani off yesterday and I had a few leaks that I fixed and I extended the wastegate actuator rod so it only boosts to 5.5 psi.Now it boosts but it dont hit full boost till 7000rpm and for some reason it will goto 8000 on a stock pm6.It pulls hard at 7200rpm but I know that now where it should be boostin.I checked the turbine for oil and there was none so I know the turbo is fine? Any ideas?
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Old 03-24-2004, 06:35 PM
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Default Re:2 1/4 downpipe and 1 7/8 exhaust

What are you using as a filter on the turbo?
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