>>28698492 (OP)
Since this thread is shit, I'll dump some wisdom to help you fellows along. First off, drag.
Drag force=atmospheric pressure x frontal surface area x coefficient of drag x velocity^2.
Double any one factor, double the drag. Double the speed, quadruple the drag.
This is why aero optimization is important, a 5% reduction in overall drag at 100kph means it's a 20% reduction 200kph, and an 40% reduction at 300kph. So how can we squeeze out every percent?
If we take the standard car, the fractions of drag is as follows
Shape/configuration - 33%
Engine cooling - 33%
Underbody - 20%
Wing mirrors 5%
Tires/flaps 10%
Antennas, handles, and other extraneous bits <5%
We can't do much about the shape of our car, or the things like door handles and antennas, but we can do something about the cooling system and the underbody.
Firstly, cooling. Your engines cooling system is designed to keep the engine cool in death valley, at noon, fully loaded with kids and the dog, towing a trailer uphill, with the AC on. All this to say that you probably don't need your maximum cooling capacity, particularly in the winter. If you're not demanding maximum output, or or even half output all the time, it may be worthwhile to cover your rad air inlets.
As a result, this will also reduce the underbody turbulence as the rad air typically has two places to escape, the windshield cowl, and the wheel openings. An underbody tray can be made cheaply from coroplast, which can prevent air moving under the front bumper, and into the engine bay, and keep it nice and streamlined until about halfway down the underside of the car. You can go all the way to the tail, but it's not as much return on your investment.
These two things on their own would cost less than 75 Canadian pesos to implement. Without CAD or a wind tunnel, it's hard to quantify the actual gains, but I would not be surprised if the above squeezed 5-10% a minimum.
