polishing intake runners worthwhile?

[Axel Rietschin]

From: "Tom Parker" <tom at carrott.org>
> Ludis Langens <ludis at cruzers.com> wrote:
>
> >Books that I've read say that the turbulence _increases_ airflow -
> >something about a smooth surface causes lamular flow along the surfaces
> >(with a dead spot in middle of the runner), while a rough surface causes
> >the whole runner cross section to be used.
>
> This is quite wrong. The reduction in flow due to turbulance is quite
> dramatic, especially in very small tubes where I have practical
experiance. I
> have no idea what sort of difference it makes in automotive applications.

There is maybe some sort of relation between the tube diameter, fluid
viscosity and speed, and wall roughness?

I've seen a World Rally Car intake manifold (on a Cosworth YB engine built
by Mountune Racing for Ford official entries in the world championship) and
it was *not* mirror-polished. Some engine builders ( like
www.pumaracing.co.uk/head01.htm ) say polishing the intake and exhaust ports
is a complete waste of time.

-Axel


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