I have a 70mm testpipe mated into a 60mm single exhaust.

Question is, would it be better to run a 60mm testpipe rather than a 70mm.

I was thinking it would flow better, just asking.

Thanks for any help.

 

You are sorta creating a bottleneck in your system from going to 60-70-60, but its not going to make a real difference. I have a 60mm on my oem exhaust and love it. If your not planning on uprgrading the exhaust diameter you might as well get a 60mm. Your not going to be able to tell a real difference, anything is better than the restrictive oem cat there though. Are you thinking of upgrading your exhaust you have to anything bigger than a 60mm?

 

same thoughts here also. I plan on mating my 63mm exhaust wit a 70mm test pipe. I just thought that it can somehow make a venturi effect to the exhaust system thus give gains. Wont it?

 

From the header to the exhaust tips, you do no want your exhaust to shrink. By putting a 70mm test pipe to a 60 or 63mm cat-back your creating that bottle neck. Its not going to hurt anything, but its not going to help either. Just thinking about it, doing that might slightly hurt the airflow. Its better to have the same diameter piping through the whole exhaust. Its okay to have a 70mm exhaust on a smaller testpipe or oem cat since the exhaust ends, it doesnt shrink after it gets to bigger diameter pipes.

 

Thanks guys, alot of help.