hello i am new to this site. i was doing some research on test pipe/hfc. A lot of threads i read on here said 70mm hfc/tp is better than 63.5 because according to some research you make more power as the size increases or remains the same. But along one of the thread i read, few people mentioned that matching the hfc with the header size yields more power than matching the hfc with the catback size. After reading that it made me think a bit. If 70mm hfc is really all that better why would companies even make the 63.5mm size and why would people even buy them. So there must be some truth about the header and hfc size?

So basically my question is who is telling the truth and which one is better or at least in my case. I plan on getting the 3 in berk cat back exhaust and probably keep the oem header. And no i do not want the berk headerback. thanks!!

 

Gernby has done the research on this. You can read up on that if you like.

My link

A 70mm test pipe will make more power than a 60mm test pipe when paired with a 70mm exhaust. The reason for 60mm test pipes is the stock exhaust and other exhausts that are 60mm. You dont want to run a 70mm test pipe to a 60mm exhaust and have a bottleneck.

 

thank you. that was lot of great info in the link but im still kind of confused a little it. If i get a 3 inch cat back would the 70mm hfc be better even if its different size from header and the catback or would the 63.5mm hfc be better because it matches the size of the header.

 

Match the cat with the cat-back.