Exhaust, midpipe questions

[justinf67]

I am in pursuit of all avenues to gain a little extra power from from my Z. I have added the KN intake, had an exhaust shop delete my 2nd cat and today I bolted on a ksk axleback. While I was down there installing the axleback, I was pretty shocked to see how tiny the midpipe piping is. I knew it was small, but seeing it was def an eye opener. I did some research and it seems p2r and t1r are the two main midpipes out there. p2r is 2.5'' and t1r is 2''. I figure that last exhaust restriction will free up some hp, but havent seen any dynos on how much. Is the p2r too large of a pipe at 2.5?

[B-rad]

Some say it is but I love mine I had the p2r until I just had it made out of 2.5" stainless.

[Old School]

If you are going to get forced induction, 2.5 may be fine. But on an NA car with only 1.5 liters of displacement it is way over kill. I would suggest going back to the muffler shop and have them put on either a 2 inch or at most a 2.25" pipe for you. No need to spend extra money on a brand name. I have the P2R (would have gone custom but didn't think about it then) downpipe which is 2.5" I believe, if not bigger, going to 2.25" pipe and resonator going to 2" axle back.

[samuel]

Originally Posted by Old School

If you are going to get forced induction, 2.5 may be fine. But on an NA car with only 1.5 liters of displacement it is way over kill. I would suggest going back to the muffler shop and have them put on either a 2 inch or at most a 2.25" pipe for you. No need to spend extra money on a brand name. I have the P2R (would have gone custom but didn't think about it then) downpipe which is 2.5" I believe, if not bigger, going to 2.25" pipe and resonator going to 2" axle back.

This guy hit the nail on the head.

First of all, i would like to say that Hondas engines breathe pretty good from the factory. You wont see much in terms of gains from simple bolt-ons in most of their engines.

In any case, adding 2.5" exhaust will add (almost guaranteed) no more horsepower than 2" or 2.25" piping. I know from many other cars that the "a-pipe" or down pipe tends to be the most restrictive anyway. If you want to replace any section of the exhaust, look at that.

All that adding piping larger than 2" or 2.25" will do (if anything) is shift the power band.

[TurboKits.com]

Correct, we just did an exhaust on a Veloster 1.6L and lost power at 2.25 - 2.5" and gained it back with 2". Bigger isn't always better.

Originally Posted by samuel

This guy hit the nail on the head.

First of all, i would like to say that Hondas engines breathe pretty good from the factory. You wont see much in terms of gains from simple bolt-ons in most of their engines.

In any case, adding 2.5" exhaust will add (almost guaranteed) no more horsepower than 2" or 2.25" piping. I know from many other cars that the "a-pipe" or down pipe tends to be the most restrictive anyway. If you want to replace any section of the exhaust, look at that.

All that adding piping larger than 2" or 2.25" will do (if anything) is shift the power band.