having just removed the standard manifold, ive measured the exhaust ports in the head to be 38mm, and also the manifold to be 38mm entries, exactly the same!
whats the crack here then? thought the manifold was smaller and hence restrictive in standard form?

anyone know the measurements of the impreza exhaust ports (cylinder head)?

thanks, ian

oh yeah, that standard up-pipe is going!

 

What you replacing the up pipe with?

David

 

hi mate,
i may just make one myself, with internal 2" dia. it isnt off yet though, but the rest of the manifold is. im porting the manifold, swapping the up-pipe, and replacing the turbo.
only just got up, so better go and do something now

cheers, ian.

 

oh forgot to mention, if i dont make my own, ill just order one from PE or scoobysport.
cosie convert got his from scoobysport and reckons its great

 

bet your wondering why it says 5 replies and only 4 replies? NTHell is to blame for that one

took mine off on tuesday only to find the same, thought they were going to be miss matched but looked ok to me, will end up porting to match the gasket size


kev

 

Must agree, when I first seen inside one I thought WTF ? same diameter ! but then if you look at any 'proper' racing manifold, they are stepped up in diameter.
There was a popular 'anti-reversion' theory on this. Stepping the exhaust to inhibit reversal of the gasses during the crucial cam overlap phase.
Sounds a good theory to me........if nothing else, my exhaust weighs less now so the car MUST be faster

Andy