Will it help?":
Thread Starter
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Junior User
Joined: Jul 2006
Posts: 95
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Will it help?":
95 PSD I have changed the down pipe and thats all.
I read on here a while back that the exhaust on these, 3", I believe, is a good system and not worth messing with. If not I was going to remove the cat and add a better muffler.
Should I?
I read on here a while back that the exhaust on these, 3", I believe, is a good system and not worth messing with. If not I was going to remove the cat and add a better muffler.
Should I?
Posting Guru
Joined: Feb 2008
Posts: 1,526
Likes: 1
From: Grass Valley, CA
The 4" would be much better! the less pressure you have against your turbo the better. i think stock is 3.5".
Let's compare cross-sectional area:
3.5"*3.5"*3.14159= 38.5 in2
4*4*3.14159= 50.25 in2
So you can see it will flow quite a bit more. also keep in mind that the stock system is somewhat crimped at the bends. if you have the money, go for the 4" system. everyone says it's a big difference.
Let's compare cross-sectional area:
3.5"*3.5"*3.14159= 38.5 in2
4*4*3.14159= 50.25 in2
So you can see it will flow quite a bit more. also keep in mind that the stock system is somewhat crimped at the bends. if you have the money, go for the 4" system. everyone says it's a big difference.
Thread Starter
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Junior User
Joined: Jul 2006
Posts: 95
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Thanks,
Clarify something for me, please. Just trying to get the facts.
I was told that the rule of thumb is up to around 250 hp 3" is fine, 4" about 350hp. If you put to big of an exhaust your turbo will not have the back poressure it needs to "spool up" and bottom end will suffer. I no very little about this and appreciate all the advice.
Clarify something for me, please. Just trying to get the facts.
I was told that the rule of thumb is up to around 250 hp 3" is fine, 4" about 350hp. If you put to big of an exhaust your turbo will not have the back poressure it needs to "spool up" and bottom end will suffer. I no very little about this and appreciate all the advice.
Senior User
Joined: May 2004
Posts: 119
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I would take care of the air intake as well. The stock muffler is fine. It is straight through. On my 95 I redid the exhaust and went to 4". It made it sound good in town but going down the highway the drone was very annoying especially on long trips. On my 96 I've left the factory exhaust with the exception of the downpipe and getting rid of the cat. I plan to leave it that way.
Posting Guru
Joined: Feb 2008
Posts: 1,526
Likes: 1
From: Grass Valley, CA
The backpressure you need to worry about is inbetween the heads and the turbo- that's taken care of by the inlet size of the turbo so there's no harm in putting a larger exhaust on.
The larger exhaust changes the pressure ratios pre and post turbo, which makes it spool up faster and stronger. you'll build more boost faster, which means more power and better fuel economy, as well as lower EGT's. You only have a downside when you go over 5". the HP thing is how much horsepower the Exhaust can deal with before it becomes restrictive. the stocker isnt good at all b/c of the crimps, the 4" is good for up to 450 or so, and the 5" is pretty much good until you're talking about 750-800 (?) horsepower...
The larger exhaust changes the pressure ratios pre and post turbo, which makes it spool up faster and stronger. you'll build more boost faster, which means more power and better fuel economy, as well as lower EGT's. You only have a downside when you go over 5". the HP thing is how much horsepower the Exhaust can deal with before it becomes restrictive. the stocker isnt good at all b/c of the crimps, the 4" is good for up to 450 or so, and the 5" is pretty much good until you're talking about 750-800 (?) horsepower...
