how much power loss with 3" exhaust
 

Hey guys, I know and 3" exhaust isnt the best choice for a N\A b series but I got a mint 3" cat back for when I installed my turbo on my B18c1 thats going in soon but not having a huge budget and my tranny needed a bearing kit I desided to rebuilt my tranny to a sick 4.9 final drive race tranny with kazz lsd so turbo isnt the best idea now plus i just bought a house so my car play moneys pretty much gone now.

So how much power will I lose if I stick with my 3" exhaust, my motor will have all the parts for my b16 plus some more which are a cold air intake, jdm Mugen type r headers 2.5" outlet, a new AEBS gsr intake manifold ported to 68mm, skunk2 68mm throttle body, fuel pressure reg, aem fuel rail(if the b16a 1 is sized for the b18c motor), adjustable cam gears, chipped p28 with a new tune.

Will I get enough back pressure with the 2.5 header outlet, 2.5" test pipe and then 3" catback to an N1 style muffler?

bump

Things sometimes run a little slower here, so please be patient :smile:...hopefully someone will be able to give you the info you're looking for.

I can't say numbers because I never dynoed. But, I had a 2.5" on my B16 however preferred to drive straight header. I lost enough torque to notice but I gained enough top end power to notice. Your 3" should be similar to me driving straight header. Just make sure you have enough back pressure so the reversion effect don't happen.


Also a short ram is your best friend in the higher rpms. I eventually put the air filter directly on the TB. This combo of open exhaust and filter on TB made my 90hatch pull like a raped ape high end. I mean supercharged cobalts had trouble. Given I had no power out of VTEC but totally worth it.

My philosophy is why try to add power where you have none to begin with add to what you have. In other words why bother with low end when honda's have none to begin with add to the high end time better spent.

I hope this helps. Just wish I had dynoes.

There's actually no such thing as "back pressure". There is rather, an optimal flow velocity which helps scavenge exhaust gases from the combustion chamber. The larger diameter the piping, the higher rpm that optimal scavenging will occur.

Long story short, where do you want the power? If you still want some decent mid-range power along with top-end, then go with 2.5" piping. If you only want peak power and no mid-range, go with 3".

IMO, useable power is always better than peak power. Having no power below 5000rpm on the street will suck.

Good luck. :)

thanks for the info guy thats pretty much what i thought. I want as much low to mid range as I can get I for autocross on those tight corners so I should go 2.5, i do have a really short geared tranny to help with that but still..... so anyone want to trade a mint 3" exhaust for a 2.5" lol, i live an hour north of Toronto.