Re: Throttle Body & Intake Manifold Polishing

[OorQue@aol.com]

> Also, because of the laminar flow nature of the air and fuel moving 
>  through the passages, I think that making sure the walls are not 
>  too rough is a minor concern.  There is more flow in the center of a 
>  moving air mass, or a river, than there is by the walls, or by the 
>  banks.

As I understand it, the reason why the surface should be left slightly rough 
is to discourage laminar flow from occuring ... in this situation, you're 
*not* trying to encourage air to flow smoothly over the surface but increase 
the volume of air that flows through the port.  The boundary layer that 
develops next to the surface when laminar flow occurs is dead (it doesn't 
move) and thus reduces the effective size of the port.  

>  Shape is more important, and as Jeff G mentioned a while back, 
>  the "outside corner" is more important than the inside.

My reference was specifically to the intake ports in the head and not the 
intake manifold.  Based upon the limited flow testing I did, the stock ports 
were more restrictive than the MC intake manifold.  In other words, when I 
tested the flow without the manifold attached (using just a molded clay dam 
around the port), the flow didn't increase much.  After the ports were 
modified, however, adding the stock intake manifold did reduce flow a bit at 
full lift.  Although I didn't spend much time testing the manifold itself, 
the brief testing I did do suggested that the restriction isn't in the 
runners but the throttle body and the Ur-Q throttle body I tried (which 
doesn't have the little aluminum wedge on the throttle plate that's on the MC 
throttle body) flowed somewhat better.

Of course, my testing was simply measuring changes in flow on a relative 
basis and doesn't address any issues about driveability.  Big flow numbers 
are nice for racecars that spend most of their time at WOT but not 
necessarily for street cars ... YMMV.

JG