ive always used 3 inch piping on all the stuff ive done.....however i have a customer who just scheduled me to make him a 3 inch downpipe leading into a 3.5 inch exhaust for his GSX...he's looking to make around 600 horsepower.

at what horsepower level does switching to something bigger than 3 inch come into effect? i considered doing something bigger than 3 inch for my car..but i think it might be over kill. im sure i'll be int he 500-550 horsepower range. any opinions/sugestions/dyno before and afters?

price is a factor for my car as well. only place i have found 16 gauge 3.5 inch piping is from burns.....i havnt looked too too hard yet though. i used to get thousands and thousands of dollars of stainless from burns...but have recently found it much much cheaper through the grapevine of people i know...however they only offer up to 3inch. its just tuff paying more than double for .5 inches!!!

i know the burns guys browse around here..no hard feelings!!!! hahaha...i still get certain things froma ya!

 

i have an electric cutout on my downpipe,about 3" after the turbo.my exhaust consists of 2.5" mandrel piping with no cat and a straight thru muffler.the power difference with the cutout open is very noticeable(at onlt 12psi).that also seems to be what everybody else i've talked to says that is using some kind of cutout or dump pipe-even people with full 3" exhausts.everything i've ever seen basically says that you can never go too big on the exhaust with a turbo;the less restriction,the better.3.5" piping does offer a big volume increase over 3" piping,but you've got to take into consideration other factors too.one thing is getting 3.5" piping under the car.i don't know about the Eclipse,but i know on a Honda that 3" is very tight in some places-3.5" would be getting near impossible.as you also mentioned price,you have to take that into consideration if the only 3.5" pipe you can find is expensive.the main thing though is performance.obviously if you're willing to spend a lot of money and time to make the 3.5" piping work,you're very concerned with performance.think about how after all that time and money you've still got more backpressure than you would with a simple,inexpensive 3" dump right off the turbo.if either of these are street cars,another consideration is sound.with a cutout you can run a smaller diameter,quieter exhaust to prevent attention from the cops,and still have the max performance possible when needed with the cutout.

Chris

 

jegs sells 3.5" aluminized