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Old 07-18-2017, 05:37 AM   #21 (permalink)
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Simba - '05 Seat Leon FR
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Originally Posted by Daveedo View Post
As for the undertray it seems as though the amount of benefit is dependent upon how high your car is and how rough the underbody is. If your car sits low to the ground already then the undertray may not be that effective. However, the higher it sits and the rougher the underside then it may have more of an effect. That's what I gleaned from reading a VERY long thread on the subject. If I misinterpreted it then by all means let me (and everyone else) know.

PS When doing your aeromods try to do the ABA testing so you have before and after mod baselines for comparisons. Thanks.
I've tried to cover as much as possible from the rough parts of the underside with a tray on my car. Less for mileage improvements, although they are, but for a better handling at speed.

Original: small undertray before engine, entire lower side of the engine bay open to air, floor mostly flat from behind the front axle subframe to rear axle, save for the exhaust tunnel.

Afterwards: full undertray from a Seat Leon 1.9TDI, from front bumper lip to behind front axle, two Coroplast additions to seal entirely the floor before front wheels, aero shaped deflectors in front of the wheels patterned on those from a SLR McLaren, rear undertray from rear axle to the middle of the spare wheel well, two small undertrays behind rear wheels to connect the bumper lip to spare wheel well, two boat-tail fins behind rear wheels.

Patterned everything on factory undertrays from economic version of Skoda Octavia - green in the picture. Did not use the undertrays in the middle of the car, between axles, as the floor is mostly flat there.

Most aero mods have minor effects, but they can be felt. First, fuel mileage improved visibly when running long distances at steady speeds. Then, wind noise diminished. Third, handling was slightly better, car is more steady in a turn or at speed.

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