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Old 08-09-2011, 04:40 PM   #31 (permalink)
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Join Date: Jul 2011
Location: Tucson, AZ
Posts: 147

Frontier 2wd 2.4L 5 speed - '98 Nissan Frontier XE
90 day: 27.87 mpg (US)
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Originally Posted by aerohead View Post
With respect to the airspeed under the car,as a function of ride height,my thought is that because of the plan radius of the front airdam,that air is being channeled around the car as much as the rulebook will allow,and while the air volume under the car will be an arithmaic function of the gap between salt and dam,the actual velocity remains a fixed fraction of groundspeed,as the dam doesn't aggressively funnel air under,but rather around.
I would agree. By lowring this car so low and adding an extra low nearly dragging air dam, the air volume under the car is minimized reducing the benefit of the belly pan.

Since the underside of a car is a restricted space, car above, road below, any drag (disruption of flow) will only further increase the presure as the air must find a way out no matter what restrictions it encounters. That is why, epecially on a car that is low to the ground, you are better off trying to eliminate flow under the car alltogether. It this case, they did a very good job of that from the front, not so much around the sides. If they added side skirt air dams to further reduce underbody flow, you would see even less gain from the belly pan, aproching zero the closer the skirts are to the ground.


Best 15-mile commute city/highway mix: 37.7 mpg
Best tank so far: 31 mpg

Last edited by graydonengineering; 08-09-2011 at 04:46 PM..
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