Say you have a zpi stage 0 or some other similar kit. What would be the pros and cons of a 3inch exhaust?

And at what hp would a 3inch become a neseccisity?

 

Depends on your plans, 2.5" will do for everyday.

3" if your making 400whp+

 

yes but say you have around 240 250 whp what would the 3inch exhaust do? WOuld it add anythign besides louder exhaust.

The reason I am asking is a few people I know with turbos keep telling me 3 inch exhaust is much better because the turbo will spool slightly faster, youll make more hp and the turbo will not die out at redline. They werent talkign about 400 hp mosnters they were talking about cars with in the 240-280 range.

 

Although a 3" isn't NEEDED for power until over 300 its never a bad idea. In a turbo car the less amount of backpressure the better.

 

DSM's for years have been putting 3" exhaust on their cars with under 260hp.

The less restriction you have the better. A 2.5 inch DP and a 3 inch catback has less overall restriction than a complete 2.5 inch system. You keep taking away restrictions and you will add power. So Stock sucks, complete 2.5" is good, 2.5" DP with 3" catback is better, full 3" is better than that and nothing at all is the best. There is no in depth physics about it, it's just as simple as less restriction is best.

 

Hmm I would recomend reading Corky Bells book Maximum Boost. It will tell you alot about what your asking... The problems that might arise and the gains you will see.

I will leave the rest to Corky as he explained it best...

 

All I have to say is be VERY careful fitting 3" back.. I had it, and ended up having to go with 3" crushed for the S-Pipe due to the 3" mandrel bent pipe hitting my drivetrain..

 

yes thats the main spec that i wanted how would a 3 inch exhaust be w a drop of 1.5 or so inch, probably scraping all the time right? Is anyone w a turbo running a 3 inch exhaust?, if so what any idea of the gains?