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T3: RE: intake manifold polishing


>From a pure Aeronautical standpoint, you WANT the air
to become turbulent for a couple of reasons.  I'll use the 
analogy of a tube to simplify the description.

Air flowing against a smooth surface produces a condition
known as a boundary layer.  The transition of air velocity 
from zero at the tube wall itself to the highest velocity at
the center takes energy, resulting in less air flow.  
All that air rubbing smoothly against itself reduces the 
amount of air available.

Weird as it may seem, a small layer of turbulent air at the
tube surface allows the remaining air to move at a higher
velocity, producing more total air flow.

Another analogy is sliding friction is less than static friction.
Air moving against itself smoothly is like static friction.
A layer of turbulent air provides a 'lubricant' to allow
sliding friction as a break between the moving air and the
zero velocity tube wall, resulting in more total air flow.

Whew, hard to remember stuff from way back in college
Aerodynamics classes.  As for Type3 content, I bought
my '67 Sqbk while I was taking these classes, and thought
about applying some of the principles, but didn't.
(that was 20 years ago, yikes! time flies)

I did do the calculations to determine the maximum velocity
for a vehicle with given constants such as HP, frontal area,
friction coefficient, etc.  It worked out to be 84 mph.  I actually
tested it out to find it was true, I maxed out at 84 mph.
Wish I still had the formula to perform this calc.

- Jeff   Iwanna21/23windowsunroofDeluxewalkthru!
to be used for daily driving
'80 Westi  (2)   BOTH FOR SALE
'66 Bus, Kombi FOR SALE
'22 Piano, upright Kohler & Cambell FOR SALE
'67 Sqbk    '64 Ford Crewcab 
'87 Subaru 4WD   '97 Nissan Quest
Grass Valley, California, USA
Jeffrey.Carver@Aerojet.com
- - - - - - - - -snip - - - - - - - - 
>> has any one ever polished the inside of there manifold??? I want to try
to
>> clean it up and seeing as I am just waiting on my Bankruptcy to get
>> finished ( singing the paper work Thursday being filed Friday ).
>> The inside of the manifold is s rough I think it would help immensely but
>> how do I do it ?????
>
>I have heard that a rough intake manifold promotes turbulence which
>is a good thing.  It helps the fuel/air mixture to mix more
>thoroughly.  It is still a good idea to take the sharp corners off
>the bends and do other things which promote better breathing.
>
>The exhaust manifold is a good thing to polish as this minimizes heat
>loss to the walls.
>
>Jim

"...a rough intake manifold promotes turbulence which
>is a good thing. "

I'm not so sure about this.  If this is so then why do racers want the
intakes, valves, and even the interior throats of carbs polished???

Air volume at a higher rate!

Rough pipes decrease the flow velocity of the air which makes the engine
starve for fuel mixture right?  I can see the "rough causes mixture" in
theory, but if this is so, wouldn't VW have added a texture to the pipe?

And for polishing the exhaust manifold... Where?  Do you mean the interior
of the heater boxes? I am unclear as to the location you mean.


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