[ta man]

Originally Posted by srmmmm

Engine Masters has had some good episodes on this subject and determined that a 3" diameter extension from the collector. 18" long is the ideal setup for maximizing torque. They also tested a 3" single pipe system against 2-1/2" duals and found the single to be as good as long as the y-pipe was far enough back from the engine.

In another episode, they evaluated cut-outs, especially how the dump pipe was spliced into the main and got some very surprising results. Low rpm performance can be impacted very negatively because of pulse reflection back towards the engine from the dump pipe.

In all cases though, A/F ratio needed to be adjusted with rejetting.

I don't believe 18 inches is the "ideal" setup...it is the more common length. Every engine combo and header combo will have a different length.
3 single pipe vs 2.5 duals is fine for smaller hp builds I'm sure..but either is grossly small for higher hp.

I did take interest in the cut out video, it for sure showed there is an ideal spot for cut outs...many street guys will just do it for sound not realizing it is a hp loss but sounds "cool"

The test I'm interested in and have never seen is the X pipe vs the collector extensions