While my engines out (GTi-R SR20 DET)

I have decided to polish the outside of the Plenum Chamber and maybe the Inlet Manifold (Sand down with wet and dry then use a polishing kit).
Obviously the outside is just to look nice :D But...

I have also decided to polish the inside of the Plenum Chamber, under the assumption it will help with air flow. But I am hearing reasons for and against this... Reasons for is that a polished surfure will help air flow, opposed to against that the rough surface is forcing the air to circulate within the chamber?

So im a bit confused. I have already started on the inside of the plenum, there is a massive cast line which can’t help air flow which I have taken off in the process.

Any views? :)

The only benefit of rough surface for intake passages is to provide more surface area for heat transfer to gasoline coating the walls...and since our fuel is injected almost at the valve, there's no gasoline-wet walls to worry about. Polish away, though your real benefit will be the intake runners to each cylinder, not the plenum.

Thanks Slartibartfast

I will carry on polishing tonight :D