Here are things that can be done to improve your vehicle's aerodynamics:
Lower the car - Lowering the car reduces the effective frontal area, increasing efficiency. Note that this only works up to a certain point. There will be an ideal ride height for each car. According to this article, 2.7" ground clearance is a good minimum height to shoot for. According to Mercedes, "Lowering the ride height at speed results in a 3-percent improvement in drag."
Remove that wing - Many "sports" cars have a non-functional wing on the back. Removing it will improve the fuel economy. The exceptions are the small rear fairings that are designed to detach the airflow from a rounded trunk.
Clean up the underside of the car. - Installation of a "body pan", while a labor intensive operation, will provide a significant improvement in mileage. More...
If a body pan is not practical, an air dam will redirect air that would normally pile up under the car causing drag. Not as good as a body pan, but better than nothing. Should be combined with side fairings.
Fair the wheel wells. - Yeah, this looks funny, but completely covering the rear wheel well will help improve efficiency. While the front wheel can not easily be completely faired due to clearances needed for turning, a partial fairing can be made. In addition, fairings can be added in front and behind the tires to help transition the air around these large appendages.
Clean up the front of the car. Basically the smoother the better. If the car has a large air intake under the bumper, it may not need that opening above the bumper (they are often just styling cues). An aerodynamic plastic, composite, or foam and duct tape panel can be built to cover the opening.
Remove the side view mirrors and instead use a remote camera system.
Replace large whip antennas with smaller powered antennas.
Vehicles with steep windshields can benefit from a hood fairing to help smooth the transition of air between the hood and windshield.
A small "tail cone" can be affixed the the rear bumper to help transition the air from under the car.
http://www.recumbents.com/car_aerodynamics/#Car side fairings
Lower the car - Lowering the car reduces the effective frontal area, increasing efficiency. Note that this only works up to a certain point. There will be an ideal ride height for each car. According to this article, 2.7" ground clearance is a good minimum height to shoot for. According to Mercedes, "Lowering the ride height at speed results in a 3-percent improvement in drag."
Remove that wing - Many "sports" cars have a non-functional wing on the back. Removing it will improve the fuel economy. The exceptions are the small rear fairings that are designed to detach the airflow from a rounded trunk.
Clean up the underside of the car. - Installation of a "body pan", while a labor intensive operation, will provide a significant improvement in mileage. More...
If a body pan is not practical, an air dam will redirect air that would normally pile up under the car causing drag. Not as good as a body pan, but better than nothing. Should be combined with side fairings.
Fair the wheel wells. - Yeah, this looks funny, but completely covering the rear wheel well will help improve efficiency. While the front wheel can not easily be completely faired due to clearances needed for turning, a partial fairing can be made. In addition, fairings can be added in front and behind the tires to help transition the air around these large appendages.
Clean up the front of the car. Basically the smoother the better. If the car has a large air intake under the bumper, it may not need that opening above the bumper (they are often just styling cues). An aerodynamic plastic, composite, or foam and duct tape panel can be built to cover the opening.
Remove the side view mirrors and instead use a remote camera system.
Replace large whip antennas with smaller powered antennas.
Vehicles with steep windshields can benefit from a hood fairing to help smooth the transition of air between the hood and windshield.
A small "tail cone" can be affixed the the rear bumper to help transition the air from under the car.
http://www.recumbents.com/car_aerodynamics/#Car side fairings
