Lets talk exhaust primary diameters....

[disco stu]

On a turbo car where exhaust scavenging is not an issue and there is always going to high back pressure pre turbo, what size is considered small on a mid 9 and faster car? I have been running a set of Kenne Bell headers for a real long time with rather small 1 1/8" pipes. I have always wondered if a larger primary would be a benefit. I have been throwing around the idea of a 4 bolt flange and larger headers, but I don't know if the benefit would be worth it. Opinions?

 

[Eticket]

Disco Stu!

If I remember correctly about your combo, I'd bet that you'd benefit from a turbo upgrade with more exhaust flow before a header tube upgrade. "I" think 4 bolt is the ultimate way to go, but guys are really going fast with the new HPQ's - I believe they are still GTQ exhaust wheels with a better flowing 3 bolt housing.

 

[cool 84]

On a turbo car where exhaust scavenging is not an issue and there is always going to high back pressure pre turbo, what size is considered small on a mid 9 and faster car? I have been running a set of Kenne Bell headers for a real long time with rather small 1 1/8" pipes. I have always wondered if a larger primary would be a benefit. I have been throwing around the idea of a 4 bolt flange and larger headers, but I don't know if the benefit would be worth it. Opinions?

That's weird, my KB headers use 1 5/8" primaries.

 

[disco stu]

I dunno why I thought 1 1/8. They are 1 1/2. the ATR's are 1 5/8 if I recall correctly. I remember KB advertising that there was no need for the competitors larger pipes and hurt spool up time. Things have come a little ways since then though.