Exhaust Manifold.

[Mr Whippy]

The ports in the head are small too though, so having fatter manifold tubes to then constrict before the collector won't do much for you.

I think it's important to keep the flow smooth so constant cross-section sounds good, and as Poodle said, just taking time on details is probably gonna get you more benefit, so gasket matching would be a good step.

Also consider the thermal mass in the manifold. Make it lighter and heat soaked off into the manifold will end up in the turbine/turbine housing instead... which might not be ideal.



PS, I was trying to check on parts box earlier, but are all HDi90/110 manifolds the same. Ie, any old k03/GT15 will swap (physically speaking) with any other hdi90/110?

I was certain they were from checking years back but I really can't remember now. I was pretty sure they were the same but can't remember now if the manifold was different too at the turbo end...

Dave