| Re: [GMCnet] Better Fuel Economy [message #95834] |
Sat, 14 August 2010 15:01  |
Gary Casey
Messages: 448
Registered: September 2009
Karma:
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Senior Member |
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Here's one way to visualize it: All air flow causes some drag. The least drag
is when flowing across a smooth surface. So to push air through the radiator,
around all the jagged shapes and out the bottom causes more drag than if that
same air flowed over the smooth outside surfaces. The lowest drag path is then
over the top (unless you fill the roof up with a subdivision of stuff) and sides
- the next is under the sort-of-smooth bottom and the worst is through the
engine compartment. Yes, if you can reduce the amount of air that flows
through the engine compartment you can reduce drag. Of course, you don't want
to block flow through the radiator is it is the ONLY place you want air to go
through. So the idea is to block any flow that DOESN'T go through the
radiator. Any kind of flap, baffle or bulkhead should help. How to get the air
out? Note the shape behind the front wheels on most race cars - it is a gentle
radius and the purpose is to provide a low-drag exit for air.
Just some thoughts,
Gary Casey
'73 23 in Colorado
Quote:
> Every body thats watched a stock car race knows that less air through the
>radiator/grill results in more speed(less drag)
...
I'm having a hard time understanding this physically.
It is like saying a glass window perpendicular a stream of air has less drag
than a window screen of the same size?
How can this be true? If true it is complex because as the mesh of the screen
becomes coarser and coarser the drag must eventually decrease and go away since
when there's no screen there's no drag.
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