RE: Curiosity about hoods

From: Bernd D. Ratsch (bernd@texas.net)
Date: Thu Sep 23 1999 - 19:17:11 EDT


Eric,

I'm not trying to aggravate anyone, let alone confuse anyone at that...

Max "Ram" at 80 mph is .08psi. Max "Ram" at 180 mph is .4psi (that's point
4 psi. This is with a 75% efficient inlet like on a dragster, that you
would never have with our trucks (or any street vehicle). It's closer to
25% to 50% , best case!!

You cant get around physics, everyone tries. Anyway, this is right out of
Carroll Smith's "Tune to Win" racing book, as well as a basic known fact in
aerodynamics. (kind of easy to calculate.) No matter what the shape of the
inlet , (funnel, scoop, horn, etc) it doesn't matter, Ram Air just does not
exist for our cars.

Here is the formula for ram potential:
Air Density (in lbs per cubic foot) X Velocity (in feet per sec) squared,
divided by 288X32.2 (All times the efficiency factor).

It WILL, however, give you a cooler air charge which will help out any
engine..performance wise.

-----Original Message-----
Subject: Re: DML: Curiousity about hoods

Bernd,
  Im not to sure I agree with that. If you have a vacuum thats doin
what it does! And you have air rushing into it instead of it sucking it
isnt that Functionally "ram air"? Crude I know! With my hood and the
amount of space that air can collect in it, I believe its sooner than
80. Much sooner actually. At idle to about 25mph to 30mph it is not
"Ram Air". It's more like air assisted! Beyond 45 to 50mph is when it
begins to truelly be "ram air". But by the time you're 3/4 down the
track, its honestly functioning quite nicely. I personally can tell a
huge difference when I put the fiberglass hood on as aposed to my metal
buck. I believe the reason is a 50% hood gain, and the other 50% due to
the intake exhaust combination that was enhanced by the hood. It goes
back to the combination modifications. The more that match the happier
the ponies will be! Air scoops that are high above or closer to the
front of the vehicle are the most functional just due to aerodynamics.
Cowls are excellent to due to pressure zones.
  I dont know really, Im just babeling and got carried away!
Oh, I went down to the exhaust lab and talked to a guy about Cats. Stock
Cats are no where near "hi-flow" Cats. With most name brand exhaust,
their claims are pretty accurate as being whatever % better.
Eric



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