Underhood pressure

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Fahlin Racing
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Underhood pressure

Post by Fahlin Racing » Sat May 03, 2014 6:32 am

Hello everyone, hope things are going well. Lately I have on the mind is for the classes that run more of a stock configuration that catch more air than the totally dropped vehicles running the strip. I have a project for a NHRDA Pro Street truck, '85 Chevy long bed. I was thinking if hood louvers would be of any benefit or should I just create shapes under the hood to guide the air (hopefully) out to the side or under the truck?

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Jim
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Re: Underhood pressure

Post by MadBill » Wed May 07, 2014 10:26 pm

Hood louvers, preferably quite large ones, positioned as seen in various road race sedans and sports cars, can relieve significant underhood pressure. Just don't make the common mistake of expecting air to exit at the rear of the hood. The positive pressure at the base of the windshield will cause an increase of underhood pressure.
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Re: Underhood pressure

Post by Fahlin Racing » Thu May 08, 2014 6:11 am

Yes, I will have to arrange them accordlingly. I think Eastwood may carry them in small sections I think I will have to check Speedway Motors too since Speedy Bill does Hot Rod parts. Thank you for your reply!
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Re: Underhood pressure

Post by turtle » Fri May 09, 2014 4:32 pm

Ok... I have to ask... What is your main purpose for reducing underhood pressure. I am only asking so I can understand your goal.

By reducing pressure it allows more air to flow into the grill, through the inter-cooler and radiator providing better cooling efficiency. I believe that is the main purpose of those type of vents. Otherwise, I think they would block of all openings of the front end.

Also, with that being said, I am "assuming" that you are attempting to reduce the pressure build up in front of the grill area at higher speed. (less aerodynamic drag)
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Re: Underhood pressure

Post by Fahlin Racing » Sat May 10, 2014 6:13 am

My main purpose is to make this thing go through the air as easy as possible since it will not be something like a race body that goes to the ground to prevent/reduce any further air causing drag under the vehicle. Its an '85 Chevy pickup. If I feel like it I can panel the underside to reduce drag but I won't be NHRA Div one or anything so It won't be really worth that work unless farther down the road I will maybe do it.
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Re: Underhood pressure

Post by Olefud » Fri Jun 20, 2014 7:01 pm

Blocking the cooling inlet as much as possible would work better than letting the air out. By the way, a PU is more aerodynamic with the tailgate closed rather than dropped or removed.








blocking the inlet

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Re: Underhood pressure

Post by MadBill » Fri Jun 20, 2014 8:05 pm

And a back-half only tonneau cover, as on the GM entered V-6 Chev truck that ran over 200 MPH at Bonnevile about 20 years ago...
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Re: Underhood pressure

Post by Fahlin Racing » Fri Jun 20, 2014 8:37 pm

So a big square will be better completely blocked, this truck won't have small ground clearance nor big clearance like a gasser for the body panels.There will still be drag caused by the undercarriage too, but, how much that affects things I am not sure. I will have the bed covered too.

Thanks guys.
Jim "Iron Giant" Fahlin ~ A high performance car is like a guitar, you have to tune it to achieve your best operation and pull ahead of the competition.

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