Raspy Exhaust Fix, Help.

[ontarian_frog]

i got the stock size pipe on mine and its ok, want to go bigger tho, 2" to the cat, and 2.25 back....

You probably want to go the other way around. 2.25 Cat and 2 inch exhaut. The cat is usually the most restrictive piece.

[AVE0SAM]

theres only one person i know of that has gone 2.25 to 2" and that was brian and he said that you can feel gains from switch from 2.25" to 2"....which makes sense since this is such a small engine.

http://www.k20a.org/forum/showthread.php?t=38783&page=2

a little bit down on this thread a person by the name of Froth uses a formula to help calculate around what size exhaust an n/a engine needs to be effiecent.

area=3.14159265 x 1 x 1 = 3.14159265 in sq

3.14159265"sq x 115cfm = 361.28315475cfm of capable flow

then you divide that by 2.2hp per cfm which equals 164.22 hp, therefore a 2" exhaust will theoretically flow enough to meet the needs of a 164.22hp engine before youstart fighting the exhaust restriction....hard bends also play a factor in this but considering our engine barely makes over 100hp to the crank i think 2" is plently

[ontarian_frog]

+1

I heard somewhere a non mandrel bend (crush bend) higher than 45 degrees is about the same as changing pipe diameter by about 1/4 inch.