I have a B18c w/ a mugen 4-1 header w/ 2.5 collector, stock civic cat and stock civic exhaust. I'm planning on replacing the catalytic converter for a Hi-flow cat and put a catback exhaust system (Apexi WS). My question is, should I get a 2.5in piping all around or should I keep it at 2.25in? Also, does a Hi-flow cat help or just a waste of money?

 

i would stick with 2.5 pipes and the hi flow cat will add some power though some do not pass emissions test

 

So a 2.5 inch piping will benefit me more than a 2.25. Would I gain or lose power. It's a stock motor with i/h/e. I'll be adding a catback soon. I just wanna know if I'd benefit from a bigger piping. Also, does anyone know what size piping a stock ITR has, from header to exhaust? Thanks

 

how did you get your 2.5" collector to match the stock cat?

 

Used a donut with a 2.25" inch hole. Basically converted it to 2.25"

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by blkcivicpn0i &raquo;</TD></TR><TR><TD CLASS="quote">So a 2.5 inch piping will benefit me more than a 2.25. Would I gain or lose power. It's a stock motor with i/h/e. I'll be adding a catback soon. I just wanna know if I'd benefit from a bigger piping. Also, does anyone know what size piping a stock ITR has, from header to exhaust? Thanks</TD></TR></TABLE>

Overall you will eventually have more hp with a 2.5" than a 2.25". The reason why the ITR has a 2.5" header to a 2.25" piping is because it was made for circuit racing. With a 2.25" you would have better throttle response, pedal pressure, and the power needed for low rpm turning where you need the constant pressure. If you are into straights you should go for the 2.5"...you will have more power...probably somewhere around a 1-2 whp more than a 2.25. Maybe even 3hp! WHO KNOWS?

Just image your piping, being simaliar to a turbo. The smaller the faster the spool, the bigger...the slower the spool but with the bigger high end.

 

Thanks!! 2.5" it is.

 

id definately get a hiflow cat though too.

they can be had for quite cheap at http://www.kteller.com i got mine there and was very pleased with it.