anyone know of a rule of thumb for exhaust system diameter/max bhp for a normally aspirated exhaust system on a tin top, i currently have a 2.5" system which is a bit noisy and want to swap it to a 2" system but wonder if a 2" system is to small for 180bhp??

I hope not I have just gone 2"... It was recommended to me by an exhaust manufacturer...

Dave B

You may notice a slight drop off at the top end, but I'd say that your choice of silencers will play a bigger role.

We used to fit 3" pipes on 300hp turbo nissans to give you an idea.


I wouldn't worry about it to be honest!

[Edited on 1/8/10 by PSpirine]

its more to do with engine(cc) size then broken down into cylinder size(cc per bore) and max rpm and where you want the power.

Its a huge area to cover as such there's no rule of thumb.