Ok so thats my question...

Is it better to go from 2" header - 2.25" b-pipe - 2.36" axle back (ie stepping up)

or

2.25" header - 2.25" b-pipe - 2.25" axle back? (keeping the same diameter through out)

 

I went 2 1/4 from the cat back, and it was just fine.. "stepping up" would just be a waste of money

 

I would imagine that stepping up is better than nothing. Anything that reduces backpressure is good and the resistance of the exhaust is a function of length and diameter.

But if you've got options, just go full 2.5"

 

Gagnar FTW

This man speaks the truth.

 

I thought 2.5" was overkill on the average Acura/Honda engine?

Lets face it, the average person modding these car's isn't doing much more then dropping it, I/H/E and MAYBE cams....from what i've read...60mm is even overkill for that

when i was driving around with no exhaust(cracked/disconnected) after the resonator...vs. now with a 2.25" Type R catback....the car *feels* much more peppy with an actual exhaust....back pressure is good...as long as its not too much

 

The only real problem is the sound (and price). The idea that backpressure helps with power is just a myth. If you're sticking ONLY with boltons there may not be a big advantage of going above 60 mm, but if you're planning any engine building at all (ie cams) you'll be glad you went with 2.5"

A hidden advantage is that the best headers all have 2.5" collectors, so if you go 2.5" cat and catback you'll be able to mate with a 2.5" collector without stepping down. I'd bet that even with stock cams a car with a 2.5" replica header mated to a 2.5" exhaust will make better power than a car with a ITR-copy mated to a 60 mm or smaller exhaust.

 

Whats the collector size on your header?

 

OK to be 100% honest...Right now my exhaust is a mixed mess...i'm waiting for parts to be delivered....BUT right this second i have a stock LS exhaust manifold, a High flow 2.25" carsounds cat(i'm 76% sure, its a long story), a stock Type R 2.25" b-pipe and a Stock 2" LS Axle back

Next weekend i should be installing a Type R 2.25" Axle back and a Greddy 4-2-1 header, which i believe has a 2" Collector

I'm trying to figure out if its worth buying a WS2 axle back which is 60mm...this was the reason for the first post....

If there are positive gains from stepping up exhaust vs keeping with the same diameter...i may buy the larger WS2 axleback...if not, i'm good to go

 

I don't think the gains will be worth the cost of a new axleback at this point.

 

There is no such thing as back pressure! Search if you don't believe me. When building an exhaust you will want to increase the exhaust gas flow velocity if staying N/A. and increase flow volume if going turbo. build accordingly. If you just want your car to sound loud, just get an axle back.

 

ok, so does exhaust gas flow velocity increase better with a stepped up exhaust deisgn or just a larger diameter then stock exhaust design?

I thought exhaust design had more to do with Pulse width and size then just velocity

 

Only on racecars. On cars with mufflers, cats, and OTS headers, the pulses get broken up before they can have much of a scavenging effect, or so I've heard.

I think you're splitting hairs at this point, especially since you've already got all your parts. Keep your header and enjoy it. If you ever start doing more engine work in the future, maybe you'll feel like getting a ful 2.5 - 3" exhaust then. That's what I would do (have done).

 

Cool good to know....i'm planning on staying N/A MAYBE LSV in the future...but not anytime soon...i'm planning a few other non-performance parts first, mostly brakes, suspension and buy part by part slowly for the LSV....i've got some, less then popular ideas with this car...so finding the parts i need are going to be harder then normal