[mattW]

This section is intended as a practical guide to improving the aerodynamics of existing vehicles. It seeks to act as a resource for enthusiasts who would like a step by step guide to reducing the drag on their vehicles and therefore improve range, top speed and efficiency. It aims to suggest and explain simple and cost effective ways to do so, using examples with measurable results wherever possible. The following modifications are not necessarily recommended or guaranteed to provide positive results. Each enthusiast should consider whether or not these are worth doing for their specific vehicle and use extensive testing to ensure they were effective. They should also have some consideration for EV PR, remember our vehicles are advertisements for electric cars and at least some consideration should be taken before making any extreme variations on styling. These projects are in no particular order.

Project: Lower Your Ride
Most EVs require some sort of spring upgrade to deal with the excess weight of the batteries. When you are working out what springs to use why not consider lowering your car by 2-3 inches from its original height. This reduces your total frontal area and therefore reduces drag. The following link is a step by step guide:
http://www.crxmpg.com/category/aerodynamic/
(was http://www.crxmpg.com/loweringsprings.html)

Project: Minimising Rear Bumper 'Parachute'
Often part of the real bumpers of cars are just there to cover up the parts under the car. If they are hanging down below the level of the underside of the car then aerodynamically they will gather up air like a parachute and increase drag. Aerodynamics can be improved by neatly trimming the rear bumper to a more appropriate height. See following example:
http://www.gassavers.org/archive/index.php/cuts-in-my-rear-bumper/t-1220.html

Project: Grill Blocking
An attempt at front grill blocking. This is apparently one of the most affective aero-mods and most of these are in normal ICE cars without overheating (at least in winter) so EVs shouldn't be a problem. This one completely replacing the existing grill with sheet metal:
http://www.gassavers.org/showthread.php?t=2965

Here is another grill blocking project, this time for the lower grill of a crx:
http://www.gassavers.org/showthread.php?t=2127

Project: Belly pans
The following link provides instructions on how to design, fabricate, install and test a simple belly pan for the front section of the car out of ABS plastic: http://www.autospeed.com/cms/A_2456/article.html

The second link provided detailed instructions and picture of how to construct a full body pan out of polyethylene plastic, the car is an EV so there is no exhaust or oil changes to worry about:
http://www.metricmind.com/ac_honda/main2.htm (click on the belly pan, wheel covers, door locks topic)

Third link is a very practical step by step guide to making a belly pan out of coroplast:
http://www.gassavers.org/showthread.php?t=671

Project: Rear wheel fairings
The following link is to a discussion of various improvements that are intended to be made to the aerodynamics of a Honda civic hatch. It includes detailed pictures of how to build a real wheel cover to improve aerodynamics:
http://www.gassavers.org/showthread.php?t=5723&goto=nextoldest

Here is another link with more detailed instructions specifically about rear wheel farings:
http://www.gassavers.org/showthread.php?t=850

Project: Smooth hub caps (moon/racing discs)
These link describes an attempts to customise the hubcaps to give smooth airflow and to minimise turbulence, it is done very cheaply but nevertheless quite well:
http://www.vassfamily.net/ToyotaPrius/rimscaps/RimsCaps.html

Small Material Overview:

Material	Density (g/cm³)	Young's (E-) modulus (kN/mm² / psi)
ABS	1.03	1.9-2.7 / 270k-380k
Lexan®	1.32	2.4 / 345k
Magnesium	1.74	42 / 6,000k
Aluminium	2.7	70 / 10,000k
Titanium 6Al4V	4.45	114 / 16,500k

Further Information:

http://www.hevo-plastics.com/html/liste_der_kunstoffe_tab_.html (German)

http://www.actech-inc.com/engmrgt.htm

http://www.germanlipa.de/xet/ematplast.htm#pc

http://ecomodder.com/forum/fuel-economy-mpg-modifications.php