exhaust issues

[OZ FMX]

time for the austiva to recieve a better note cause i'm tires of the crappy little hotdog thats in it and getting a new lukey muffler and getting the hotdog taken out so it'll just be one straight unit.
whi would be the biggest diameter tube to use for the exhaust befor it sounds like its constantly farting and have no power, i'be been told go no bigger than 2.25" on the inlet and out let, would this be right?

[Safety Guy]

I can't tell you for sure, but when I did my B6 engine swap, I opted for a 2" system with Magnaflow cat and muffler.

That would be my upper limit for a B3 or B6 N/A engine.

Karl

[ericsmith32]

This was posted over on a kia forum:
You need 2.5 cfm per HP
A good average exhaust system will flow 80 cfm per sq/in

Sooo ...
65 x 2.5 = 162.5 cfm needed.
A 1.75" setup will flow: PI x (r x r)
Pi x (.875x.875) x 80 cfm per sq/in = 192.4 cfm - just right

A 2.0" setup will flow:
Pi x (1x1) x 80 cfm per sq/in = 251 cfm

Just change whatever horsepower your engines putting out where the 65 is. I don't where he got the formula.. I may search for it later.