[DeTomaso] Has anyone researched hood vent designs?
MikeLDrew at aol.com
MikeLDrew at aol.com
Thu Aug 4 23:55:08 EDT 2016
In a message dated 8/2/16 7 55 50, julian_kift at hotmail.com writes:
> Hood vents are a great way to provide additional cooling in traffic, but
> perhaps limited value at high speed when the front of the hood becomes a
> high pressure area. Now you have opposing forces at play and at speed 'x'
> the pressure is likely enough to overcome that produced by the radiator fans
> (I imagine that 'x' would not be excessively high, perhaps even highway
> cruising speed). So outside air now reverse enters the hood vents or at a
> minimum restricts fan flow resulting in air that is forced under the car i.e.
> back to the original Ford design concept. A Gurney lip on the frontal edge
> of hood vents would help create a low pressure area, but I still believe
> the air from the radiators will ultimately be forced under the car at some
> speed now x+y.
>
>>>I don't know about high triple-digit speeds, but the hood is a
low-pressure area at speeds typically seen on the road (even low triple-digit
speeds). You can test this for yourself by simply unlatching the hood and going
for a drive. At freeway speeds, it will 'float' an inch or two above the
latch, as vacuum from above (probably aided by pressure from below) lifts it
slightly.
I don't know what, if any effect might be realized by introducing hood
vents with all other things being equal. Providing a path for air to exit
through the hood rather than pushing up on the underside of it might be a thing?
(Geoff Peters had a very thin carbon fiber hood, with vents, on his GT5,
and he found that at high speeds, it would deform so much by lifting in the
center, that the pin would move forward and pop out the front side of the
latch and then the hood would fly open and hover a few inches above the latch!)
An air dam, particular a proper Gr4/GT5 air dam, provides meaningful
downforce and probably helps prevent air from underneath from pressing up on the
underside of the hood, as others have mentioned....
If you look at the GT40, the early cars came with two deep triangular hood
vents, while the later ones came with a single very large vent, which was
undoubtedly far more effective.
Having said all of that, I've run my car at 130+ mph on the track with a
simple, small GTS mini air dam and no hood vents, and the car ran at 180
degrees with not a bit of front-end lift. I wouldn't assert that the front end
would be similarly planted at 200 mph, but then again, I have no intention
of going anywhere near 200 mph so it's completely academic....
Mike
-------------- next part --------------
In a message dated 8/2/16 7 55 50, julian_kift at hotmail.com writes:
Hood vents are a great way to provide additional cooling in traffic,
but perhaps limited value at high speed when the front of the hood
becomes a high pressure area. Now you have opposing forces at play
and at speed 'x' the pressure is likely enough to overcome that
produced by the radiator fans (I imagine that 'x' would not be
excessively high, perhaps even highway cruising speed). So outside
air now reverse enters the hood vents or at a minimum restricts fan
flow resulting in air that is forced under the car i.e. back to the
original Ford design concept. A Gurney lip on the frontal edge of
hood vents would help create a low pressure area, but I still
believe the air from the radiators will ultimately be forced under
the car at some speed now x+y.
>>>I don't know about high triple-digit speeds, but the hood is a
low-pressure area at speeds typically seen on the road (even low
triple-digit speeds). You can test this for yourself by simply
unlatching the hood and going for a drive. At freeway speeds, it will
'float' an inch or two above the latch, as vacuum from above (probably
aided by pressure from below) lifts it slightly.
I don't know what, if any effect might be realized by introducing hood
vents with all other things being equal. Providing a path for air to
exit through the hood rather than pushing up on the underside of it
might be a thing?
(Geoff Peters had a very thin carbon fiber hood, with vents, on his
GT5, and he found that at high speeds, it would deform so much by
lifting in the center, that the pin would move forward and pop out the
front side of the latch and then the hood would fly open and hover a
few inches above the latch!)
An air dam, particular a proper Gr4/GT5 air dam, provides meaningful
downforce and probably helps prevent air from underneath from pressing
up on the underside of the hood, as others have mentioned....
If you look at the GT40, the early cars came with two deep triangular
hood vents, while the later ones came with a single very large vent,
which was undoubtedly far more effective.
Having said all of that, I've run my car at 130+ mph on the track with
a simple, small GTS mini air dam and no hood vents, and the car ran at
180 degrees with not a bit of front-end lift. I wouldn't assert that
the front end would be similarly planted at 200 mph, but then again, I
have no intention of going anywhere near 200 mph so it's completely
academic....
Mike
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