Thread: Exhaust Size

Originally Posted by flagg

I read somewhere that for a td5 the best exhaust size was 2.5".. larger than that and you didn' get enough back pressure or something..

What size for people run for a turbo Isuzu? I assume 2.5 or 3 w/ mandrels? Does a 3 actually make a difference or just make it louder?

Thanks as always

It has been reported by some that you will overspeed a TD5 turbo if you fit a 3" exhaust. However there are plenty who have 3" exhausts on TD5s with no reports of turbo failure.

As for 4BD1Ts, myself and plenty of others have 3" mandrel bent exhausts which work well and have not caused turbo failure/overspeed.

To maximise performance, you want to reduce pressure drop post turbo, which means a large exhaust.