Cat Body Size

[simmo]

Im looking at a brand of cat that is 100 cpi .The 4.5" body flows around 720 cfm(claimed)where the 5.5" one flows over 800cfm is the 4.5" one enough for me if im chasing around 300rwkw??

How do you really know that they are flowing what they say its flowing without buying it and getting it tested yourself.

[IH8TOADS]

The inlet/outlet size will affect flow as well as body size. If you get a 4.5" body with 100cpi on a std BF dump that will be good for 300 on 12 - 14 psi (depending on other mods). Ba dump will restict slightly due to the twin exit.

Don't worry about testing. 100cpi is the latest and greatest in cats.

[simmo]

thanks for reply

[wilba]

well I found a cat with a 3 1/2 inlet/outlet and the body size is 3 1/2 is that good or should the body be bigger here is that site www.pcpa.com.au thanx

[ETM]

well I found a cat with a 3 1/2 inlet/outlet and the body size is 3 1/2 is that good or should the body be bigger here is that site www.pcpa.com.au thanx

so its a straight bit of pipe with a cat cell in it, it would flow pretty badly compared to one with a 5" body.

[wilba]

rite so I take it im better off getting a xforce or sumthin like that.so bigger the body the better?

Edited 11/02/09 09:26 AM by wilbaz

[ETM]

yeah, imagine the cat cells take up 30% of the area of the pipe is 3.5" all the way through the cat section will flow 30% worse than the rest of the exhaust system. If the section with the cat cells is say 5" then it obviously has enough extra area to make up the difference and flow as much as a bit of straight 3.5" pipe

[wilba]

thanx heaps mate

yeah, imagine the cat cells take up 30% of the area of the pipe is 3.5" all the way through the cat section will flow 30% worse than the rest of the exhaust system. If the section with the cat cells is say 5" then it obviously has enough extra area to make up the difference and flow as much as a bit of straight 3.5" pipe