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Old 07-11-2009, 10:50 PM   #1 (permalink)
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Cowl block - similar to grille block

Came across this point in the Hot rod magazine article about wind tunnel testing the Camaro that Cd pointed to:

Car Aerodynamics - Modifications - Hot Rod Magazine

Quote:
Seal the back of the hood to the cowl: This is another area that's less critical on newer cars that are already well sealed. Cowl-induction hoods have a high-pressure area at the base of the hood. Air does not travel out the back of the hood; it is forced down into the engine compartment. That air must escape through the car, causing flow disruptions and drag.
Improvement: 10-20 counts less drag, 50 to 75 in lift
For comparison, they estimate a 15 to 30 count reduction with a full grille block.

(1 count of drag - Cd 0.001)

I believe this is the same kind of block Phil referred to in testing of his CRX streamliner at Bonneville:

Quote:
A cardboard and duct-tape cowl fillet over the wiper area demonstrates a 0.28-mph improvement to top speed.
Source: http://ecomodder.com/forum/showthrea...drag-2888.html

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Old 07-11-2009, 11:20 PM   #2 (permalink)
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( There are a lot of very good aero tips in that article - it is several pages .)

I'm a little old nobody, but if I was in charge of a major forum dedicated to testing out aerodynamic mods on cars, I would invite this guy over to this forum to share some more of his tips for us.

He runs the A2 windtunnel, which is actually affordably priced, and it might even get him some business if he dropped in sometime and gave us some insight.

I would love to see him join us.
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Old 07-15-2009, 06:22 PM   #3 (permalink)
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cowl

Darin,this one's kinda context related.For ram-air it's hard to beat the forward stagnation point of the car.In NASCAR,where your drafting behind another car,you lose this ability,so the cowl area becomes the first runner-up.Not as much pressure,but some pressure,even when drafting,and it's further from the track surface and likely lower temp for better charge-density in engine.----------Cowl -induction was introduced in production Chrysler cars in the 1960s which were also racing NASCAR.It probably wasn't as "good" as front harvesting of air,but was very sexy and loaded for testoserone-packed car sales on Monday after the races on Sunday.--------------- The thing I did at Bonneville was strictly an attempt at drag reduction,and you can tell from the numbers that Honda had done a pretty good job with the CRX.
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Old 07-17-2009, 05:20 PM   #4 (permalink)
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Most newer cars are well sealed at the back edge of the hood. You don't want to seal your cowl air intake unless you don't like fresh air and want to run your AC all the time.
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Old 07-18-2009, 05:17 AM   #5 (permalink)
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HVAC cowl air intake is a good thing. Fresh air for the AC, and also probably helps the HVAC maintain positive pressure. You need positive pressure to keep the air clean and reduce the chance of getting stuff like carbon monoxide coming in
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Old 07-19-2009, 04:15 PM   #6 (permalink)
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* for competition purposes only, of course.

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