Abrasive flow finishing

[Steve Leonard]

DIYFIers
   A book out by Bartels Racing, (Harleys mainly)
Claims that they have done many tests about polished vs
a swirl finish.
   They claim there is ABSOLUTELY no airflow within
0.040" of the port wall, so they only swirl polish
their racing heads.
   The only place they claim a mirror finish is
beneficial is on top of the piston, less chance for
detonation and carbon won't stick to the piston as
easy.
                             have a great Holiday
                                    Steve L




---Chris Conlon <synchris at ricochet.net> wrote:
>
> Hi,
> 
> First I owe a big thank you to Tom Cloud, Tony
Cooper & everyone else who helped
> me out w/knock sensor info. It's amazing how black
boxes aren't so dark once you
> break 'em open ;)
> 
> > I read in an article on the net (or was it a
magazine)somewhere about the surface
> > texture of ports in a cylinder head. It was
something about the benefits of porting.
> > What they mentioned was that the exhaust side
would benefit most from having a smooth
> > finish vs the intake. 
> 
> I was thinking about the "random bumps reduce drag"
effect. Perhaps there's a
> difference between drag on an object in free space
(planes, golf balls) and mass
> flow through a tube. It seems weird, but it might
be true. Supposedly when you
> have laminar flow over a surface the flow speed
right at the surface is near 0,
> increasing (as distance squared) to whatever max
value "far" from the surface.
> I *think* that this nice, smooth flow over the
surface also provides maximum
> drag, kind of like being perfectly wrapped in
sandpaper. The bumps cause turbulent
> flow, which results in little pockets of air where
the "sandpaper" isn't touching
> you... and thus less drag.  Where I think the
difference between free space and
> a tube lies is that, in a tube, the turbulent flow
near a dimpled surface has to
> intrude into the limited flow area of the tube
itself, where it interferes with
> and reduces the smooth flow that was there. Clearly
more of a problem in smaller
> tubes. Anyway that's my thought. Someone with a
better understanding of
> aerodynamics please feel free to correct and
clarify this!
> 
> 
> > One reason mentioned for leaving the intake side
unpolished is
> > to help the turbulance effect which serves to
homogenize the fuel mixture for more
> > thorough combustion and thus better power.
> 
> I have heard this enough that I'm willing to
believe it. But it says one thing
> to me, which touches on one of my curmudgeony
theories, and that is "the fuel
> isn't evaporating thoroughly." Comments? Is this
just a well-known fact?
> 
>    Thank you for your time,
>    Chris C.
> 
> ATTACHMENT part 2 application/ms-tnef 

 

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