Outer Limits 4x4 Board

Am putting extractors on my 1.3lt power house and getting a new exhaust built behind it. Considering the original exhaust is 1.5in what size exhaust pipe should I go to.

Is 2in too big or should I go 1 3/4in for pipe and muffler.....

Unless you have plans down the track and want to "build ahead" then 1 3/4" with a reasonably free flowing muffler will do the job IMO.

Contrary to whats' "cool" there is an optimum exhaust velocity ( and pipe lenght etc etc etc ) for each engine and its state of tune and an overly large main exhaust won't achieve that.

Having said that - the sorts of gains/losses from the exhaust system are going to be near on impossible to detect by "seat of the pants" testing on a 1.3 "power house" - often the difference in exhaust note convinces people one is better than the other.

Withe such small ( read gutless ) engines the small percentage gains are VERY difficult to measure, engine dyno - yes, chassis dyno - probably, by driving - most unlikely.

So 1 3/4" is likely to be technically nearer to optimum but in the end.......

i ran 1.75 with 1.30l engine and extractors - when i went to the 1.6 i went up to 2" pipe & muffler and changed the cat to a 2" cat as well.

Most people forget the cat converter when changing the exhaust, and it becomes a bottleneck, effectively not changing the exhaust at all.

I did have a 3" tip on the end (droopy style) up to early this week, its now a 2" tip bent to 90 degrees (so straight down) to further reduces fumes in the cab - it sounds identical to the 3" tip (its quiet as).

2" max for a n/a 1.3, run a straight through muffler for best results.
Also run a cat if you arnt brave enough to run without one.