Header design

[JeffYoung]

Anyone use this resource before?

www.headerdesign.com

The primary size it recommeds for my car is AMAZINGLY small....1.25"

[lateapex911]

No fun for rotaries

[evanwebb]

The results for a 1.6 VW motor look to be pretty similar to what Stahl sells for a header. I couldn't figure out what length to make the exhaust after the collector, did i just miss that in the calculator somewhere?

Jeff your motor is basically two banks of 1.8 liter 4 cylinder motors, right? With a fairly low peak HP RPM, and not really high peak HP number either, right? That size primary might sound about right. I think the vast majority of all commercial headers are probably way too big, the size is a marketing tool...

[evanwebb]

Hey I just bought this software ($45) out of curiosity, anyone interested in sending me some info I can enter it and see what it comes with for header & exhaust design...

http://www.maxracesoftware.com/pipemax36xp2.htm

[Greg Amy]

Evan, turn on your PMs and send me a note about what info you need... - GA

[JeffYoung]

Ron and I have thought this for a while. "Old school" thinking was bigger is better. Now, smaller primaries is thought to increase exhaust gas velocity and therefore scavenging. I agree with you, smaller is probably better on a low rpm hp peak car.

I saw your pm. I'll get you the information I have here shortly.

The results for a 1.6 VW motor look to be pretty similar to what Stahl sells for a header. I couldn't figure out what length to make the exhaust after the collector, did i just miss that in the calculator somewhere?

Jeff your motor is basically two banks of 1.8 liter 4 cylinder motors, right? With a fairly low peak HP RPM, and not really high peak HP number either, right? That size primary might sound about right. I think the vast majority of all commercial headers are probably way too big, the size is a marketing tool...

[erlrich]

Ron and I have thought this for a while. "Old school" thinking was bigger is better. Now, smaller primaries is thought to increase exhaust gas velocity and therefore scavenging. I agree with you, smaller is probably better on a low rpm hp peak car.

Maybe old news, but here is a pretty good overview of header design theory: http://www.ssheaders.com/header.htm