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Old 11-14-2012, 07:25 AM   #1 (permalink)
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Engine Compartment Venting

Hi,

Currently, I am venting the engine compartment through gill slot openings in the belly pan. This is making lot of turbulence under the car, it's like having a window open. I am considering venting though the front wheel wells, where the air is already disturbed. Anybody have any thoughts or comments on engine compartment venting?

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Old 11-14-2012, 11:03 AM   #2 (permalink)
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Quote:
Originally Posted by arcosine View Post
Hi,

Currently, I am venting the engine compartment through gill slot openings in the belly pan. This is making lot of turbulence under the car, it's like having a window open. I am considering venting though the front wheel wells, where the air is already disturbed. Anybody have any thoughts or comments on engine compartment venting?
This is what has been done on the Aerocivic and on my own car with a full, front to back belly pan. The openings in the wheelwells are plenty large enough to let the air escape. Most of us on this forum already have some of the grill blocked so there is minimal cooling air going through the engine compartment. Watch your ScanGuage. I think you'll be fine.
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Old 11-14-2012, 04:39 PM   #3 (permalink)
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According to Hucho, the very best arrangement is to vent into the area on top of the hood. Venting into the wheel wells and into the underneath are equal and are half as good Cd wise, according to his book.
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Old 11-14-2012, 05:06 PM   #4 (permalink)
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Originally Posted by jime57 View Post
According to Hucho, the very best arrangement is to vent into the area on top of the hood. Venting into the wheel wells and into the underneath are equal and are half as good Cd wise, according to his book.
I think that would vary quite a bit from car to car no? Wheel wells have different designs, underbodies have different designs (or lack thereof), and hoods have different angles and shapes.

Venting under the car could be marginally better if there's one of those higher diffusers.
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Old 11-14-2012, 06:30 PM   #5 (permalink)
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Pull out the seal for the hood at the base of the windshield...
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Old 11-14-2012, 08:25 PM   #6 (permalink)
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Venting on top would put a lot of dirty air over the car body. Im going to try venting into the wheel wells and close off the openings in the under body belly pan and shoot a tuft video again.
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Old 11-14-2012, 08:46 PM   #7 (permalink)
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Originally Posted by serialk11r View Post
I think that would vary quite a bit from car to car no? Wheel wells have different designs, underbodies have different designs (or lack thereof), and hoods have different angles and shapes.
You may think what you like, as may I, as may any of us. I'm only reporting from a reliable handbook on the subject. The original paper is: BUCHHEIM, R., DEUTENBACH, L.-R., LUCKOFF, H.-J., "Necessity and Premises for Reducing the Aerodynamic Drag of future Passenger Cars," SAE Paper No. 810185, Society of Automotive Engineers, Warrendale, Pa., 1981.

Quote:
Venting under the car could be marginally better if there's one of those higher diffusers.
Reference please
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Old 11-15-2012, 11:17 AM   #8 (permalink)
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Venting on top would put a lot of dirty air over the car body.
There are some ultra high performance cars that vent radiator air over the hood for better aerodynamics. One possible downside for production cars is the chance of coating your windshield with glycol while driving, if there is any sort of cooling system failure. Also, high performance cars are designed to be driven with big engines and pedal to the floor, generating much more waste heat than your average hypermiler. IMHO if you are already using some sort of grill blocking we are splitting hairs here. Try sealing the underbody and monitor your engine temperature.
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Old 11-15-2012, 12:21 PM   #9 (permalink)
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Quote:
imho if you are already using some sort of grill blocking we are splitting hairs here. Try sealing the underbody and monitor your engine temperature.
]

it is sealed, read the first post!
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Old 11-15-2012, 02:06 PM   #10 (permalink)
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Try reading this paper "Interference Effects of Cooling Air-Flows with External Aerodynamics" . It covers how engine compartment cooling effects overall drag.

http://tech.jsae.or.jp/ijae/download...x?pno=20114635

Edit: I think you want to keep your under tray gill slits

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