Now here is the kind of common sense evidence that I was looking for. You are
exactly right, I have never seen evidence of significant water influx through
the header holes. while they may not be 'low' pressure areas, the wheel wells
must certainly be lower pressure then the engine bay.
Your comments about water spray are harder to interpret though, as the water
is not set into motion until the tire throws it into the air. If we could get
a car into a fog or smoke situation it might be possible to visualize where
the airflow is really occurring, but I'm not sure.
The last bit of evidence is that modern lemans prototype cars all have louvers
in the rear of the wheel wells, presumably to smooth airflow over the body, I
think this lends support to the existence of high pressure in the wheel wells
but since air is being ducted in to cool the brakes, maybe that doesn't tell
us anything. What we need is an automotive aerodynamicist but I think that if
we had one he'd have spoken up by now. Maybe he is laughing so hard at all of
our conjecture that he can't type?
James Nazarian
71 MGB Tourer
71 MGBGT V8
85 Dodge Ram
----- Original Message -----
From: Barrie Robinson
To: James Nazarian ; Telewest (PH) ; v8
Sent: Wednesday, August 20, 2003 7:04 PM
Subject: Re: timing
James,
One of my concerns when building an MGB GT V8 was to ensure that the engine
did not overheat. I had heard so many comments on V8s running hot because of
the cramped engine bay. So I got Australian headers that went through the
wheel arch, D & D Fabrication "heavy duty" radiator and I squeezed in a 14
inch 2,950 cfm Perma-cool puller electric rad fan. The latter achieved by a
special 3" water pump instead of the standard 4". But in my travels I think I
heard that wheel wells were low pressure so that engine air would be sucked
out through the holes for the exhaust header. This seems reasonable as the
"hole" is at right angles to the air flow. In other words the air travels
over the hole not into it. This would then cause a decrease in pressure in
the wheel arch? If you watch cars in the rain does not the water spray out
of the wheel arch not into it? Also if the wheel arches were high pressure
then the rain and dirt would be blown into the engine through the wheel arch
holes and this would be very obvious to a runner of a V8.
Maybe someone can check the theory?
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