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Old 10-08-2008, 12:26 PM   #8 (permalink)
Master EcoModder
wagonman76's Avatar
Join Date: Jun 2008
Location: Northwest Lower Michigan
Posts: 1,006

Red Car - '89 Chevrolet Celebrity CL 4 door
Team Chevy
90 day: 36.47 mpg (US)

Winter Wagon - '89 Pontiac 6000 LE Wagon
90 day: 28.26 mpg (US)
Thanks: 8
Thanked 17 Times in 16 Posts
one thing is that any air that enters the engine bay trough the grill will also have to exit somewhere. the opening at the bottom of the engine may serve as a very crude exit duct wich, when blocked could cause the airflow to exit elsewhere where it might cause a disruption in the airflow underneath and around the car.
This could be true. Behind the grille openings in the valence is wide open underneath for like 16 inches. The engine and transaxle combo take up most of the rest of the space back to the firewall. So the air coming through the bottom part of the radiator (the top is blocked with my homemade solid grille) would most likely go down under the car. The transverse V6 would help too, since it is much wider at the top than the bottom, guiding the air down and under the car. With the bellypan, who knows where it goes.

it's also possible that it restricts the airflow to your engine, creating pumping losses, or cause it to ingest hotter air wich depending on how your engine management reacts could also cause worse FE.
Definitely possible. The air intake is behind the drivers side headlight. The air normally would normally be drawn straight up from the bottom, but with the bellypan, it would have to take a more roundabout way and would probably be warmer. I didnt notice much of a difference in my temperature gauge, could have been slightly higher but if so then just a sliver.

on the other hand if the underside of your car beyond the bellypan causes enough flow restriction this may undo any benefits from the bellypan.
The engine and transaxle are close to the firewall, and the floorpan is pretty smooth, but the solid beam rear axle probably screws up the airflow pretty well. I would probably need to take a big sheet of rubber and fasten it to the floorpan and to the rear bumper, draping it under the rear axle with enough room to stretch as needed. But then theres the exhaust too.

were a dam when proppery sized could reduce underbody airflow slightly.
The level of the airdam is a bit below the engine cradle, which is the lowest part, so it probably keeps more air from under the car, where the bellypan was stretched from the valence to the cradle and helped direct air under the car.

Winter daily driver, parked most days right now

Summer daily driver
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