My mugen twin loop exhaust has a bottle neck right after the cat flange. My question is which aftermarket exhausts don't have this? Does the JDM mugen cat-back have this bottle neck as well?

Why in the world would they keep this bottle neck there on an aftermarket exhaust?

Thanks.

 

The tubing also drops in size from 60mm after its first pass through the muffler. I think it drops down to 55mm. But I'm not positive you should measure it there also.

 

Buddy Club "noise maker"

To match the opening on the outlet of the stock catalytic converter.

Will

 

tasty

 

The Kakimoto R for TypeR, the whole catback is at least 2.5", even at the so called bottleneck section!!

 

Will,

I don't think that is why. It looks like somebody put a venturi there, it goes down to about 1.6". On the stock exhaust, I would assume they put that bottleneck there to keep the gases in the cat a little longer for emissions.