The louvers work pretty well to release the high pressure area in the engine
compartment for as you have mentioned, the area over the top of the hood and
before the windscreen is a low pressure area..
Never Be beaten by Equipment
Kas Kastner
----- Original Message -----
From: Bill Babcock
To: Group44TR7@aol.com ; fot@autox.team.net
Sent: Thursday, September 14, 2006 12:41 PM
Subject: RE: [FOT] Dumb, Basic Question on Hood Openings - Placement &
Direction
Generally if you see a rearward-facing scoop it's close to the
windshield, taking advantage of the high pressure area that's usually
there. One (possibly mythological) story is that the GT40 actually has a
negative pressure at the base of the windshield--lots of cars have
negative pressure at the top of the windshield. Forward facing scoops
look to ram air, either directly feeding the carb (problematic) or
feeding a cold air box. To see what it really takes to ram air for a car
engine look at the Pro Stock drag cars. A huge scoop, well above the
slowed flow on the hood. <Insert Kas' wisdom about ram air here>.
Actually ram air can be done successfully, I've seen it on lots of
motorcycles and motorcycle-powered race cars. But you need
computer-controlled engines to really make it work.
Louvers are certainly cool looking. The theoretical purpose is to
release heat from the engine bay, the real purpose is to look oh so very
racy in a period way. Hard to say what way to face them, they probably
won't act as mini-scoops to any real purpose--the boundary layer on your
hood is probably too thick and they get in each other's way. I love the
way they look. Someday Peyote will have a few somewhere.
> -----Original Message-----
> From: owner-fot@autox.team.net
> [mailto:owner-fot@autox.team.net] On Behalf Of Group44TR7@aol.com
> Sent: Thursday, September 14, 2006 12:18 PM
> To: fot@autox.team.net
> Subject: [FOT] Dumb, Basic Question on Hood Openings -
> Placement & Direction
>
> Would someone please explain the different purposes
> served by having the air hood scoop opening facing forward
> verses facing "backward" toward the windsheid on a
> competition car.? (For discussion purposes, let assume that it is a
> TR8)
>
> Secondly, what is the primary purpose served by a series
> of louvers (Sp?) cut into the bonnet or hood? Is there any
> engineering specifics on the distance that they should be
> from each other or the depth to which they should be bent (
> angle), opening size or otherwise cut to facilitate air flow?
>
> Is there any engineering specifics (depth/spacing) on how
> to position these louvers in a row on the bonnet/hood to
> facilitiate cooler air enterring the intake area and/or warm
> air exiting hotter areas? Should the opening be facing
> forward or backward?
>
> I have seen cars with multiple rows of louvers on the
> hood and same model car with only one row. Are some of these
> guys with many rows just doing cosmetic work, do they shred
> cheese on them later for Pizzas, or is there something to be gained?
>
> Thank you in advance, Cary
>
>
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