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Old 04-02-2012, 12:26 PM   #1 (permalink)
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Lowered belly pan?

Has anyone considered lowered belly pan which might do the same thing as airdam + flat belly pan?

My car in stock form


with fat belly. same ride hight.


vent radiator and intercooler to the rear end.


What can you tell from the above pictures?
Will this reduce vortex drag? reduce lift?

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Old 04-05-2012, 09:57 AM   #2 (permalink)
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Flow Illustrator isn't a testing program so don't expect "results" from it.

The point of an air dam is to direct air away from the "dirty" underbody. The point of a belly pan is to make the underbody "clean". If you want to kill two birds with one stone just keep the pan at precisely a zero degree (horizontal) angle to the ground. This will prevent it from compressing air under the car, and you should reap the benefits of both aero aids.

For a fastback profile you'll want the rear end (behind the rear axle or wherever is convenient) to angle upward at a 3 degree angle from horizontal for maximum drag reduction. Anything steeper than about 7* back there will actually increase your drag.
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Old 04-05-2012, 01:05 PM   #3 (permalink)
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I'm not an aero guy, but the flow in stock configuration looks a whole lot smoother than either modded flow.
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Old 04-05-2012, 06:36 PM   #4 (permalink)
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reading

I recommend that you read all the Stickys at the top of the Forum page.
Afterwards,you'll be able to answer many of your own questions.
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Old 04-05-2012, 08:21 PM   #5 (permalink)
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When I was creating this thread, I was thinking:
- Smooth bottom could reduce drag (locally at least)
- Lowered bottom could reduce lift
- Increased frontal area.
- Moderate diffuser angle could reduce drag.
- Longer diffuser. probably less lift.
- Higher diffuser angle could reduce lift at the cost of increased drag.

Though I do not know if all these things add up. Mabye not.
Not many things in aerodynamics seems to be linear too.

So here are things I just can't figure out:
- Large counter rotating vortices vs smaller but seemingly higher velocity vorticies.
- Steady separation vs wake?
- If I'm not mistaken, higher reattachment point: does this have any significance?


I'm almost decided to do flat belly pan AND a detachable lower belly pan just like in the third picture for track days.
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Old 04-05-2012, 08:23 PM   #6 (permalink)
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Quote:
Originally Posted by aerohead View Post
I recommend that you read all the Stickys at the top of the Forum page.
Afterwards,you'll be able to answer many of your own questions.
I read most of them long before (maybe too long before), read several case studies, but still there are many things that I can't comprehend. I ordered Hucho's book.
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Old 04-05-2012, 09:31 PM   #7 (permalink)
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If I understood it correctly, then you are lowering car without lowering it and as lowering reduces drag, so would lowered bellypan, but as it would increase also frontal area gains from it might be lost or not, depends from how much more frontal area there will be and how much lowering reduces drag, should be possible to calculate how it will be.

Sadly I'm not able to do such calculations.

Of course there could be even more in play, but I think that is basics to get some idea?
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Old 04-06-2012, 12:56 AM   #8 (permalink)
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I put an IMPUL body kit on my 02Infiniti Q45.
(see link in signature)
That 'lowered' the car 2 inches all the way around but left the stock ride in palce.
Then I Installed a underbelly pan.
(see link below picture)
This is what you are asking about.
I will tell you that I consistantly got 27mpg (epa 22 mpg) on 5 hour trips - before joining EC and doing the belly pan or any other mod- because of the body kit and eco-minded driving. I dont hypermile. But I do engine on coast in neutral.

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ECO MODS PERFORMED:
First: ScangaugeII
http://ecomodder.com/forum/showthrea...eii-23306.html

Second: Grille Block
http://ecomodder.com/forum/showthrea...e-10912-2.html

Third: Full underbelly pan
http://ecomodder.com/forum/showthrea...q45-11402.html

Fourth: rear skirts and 30.4mpg on trip!
http://ecomodder.com/forum/showthrea...tml#post247938
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