I have done a search and do see an answer to this question because its specific.

I have a built supercharger by Endyn, port and polished job on my head, and a kamikaze header that has a modified collector at 2.5 in. on my built H22A. I am about to purchase mandrel bent piping for a custom exhaust but am not sure which diameter I will benefit more.

I hear it is good to have 2.5 because it provides some back pressure as to where 3 in is too free flowing. I also here the opposite at where you want a free flowing as possible.

So far I am pushing 242 hp and 222 tq with NO bolt ons and a hondata with 550cc injectors. When I dynoed it, the guy said that the stock header and stock exhaust wasn't free flowing enough which I understand. I just want the most power out of the car. It IS a fatass prelude but I still love her.

I would appreciate any comments or insight. Thanks

 

Anyone

 

I have always heard once you go FI bigger is better.

 

I would go with 3''

 

the bigger the better, you dont want any back pressure at all if you can avoid it

 

I say 3" just incase you plan to upgrade ur boost in the future