Aerocivic - how to drop your Cd from 0.31 to 0.17

[trebuchet03]

Originally Posted by SVOboy

I do believe newton has had that thought (of making aero body kits for ecomodders), and I definitely think it's worth a go. If I knew anything about molding and all that jazz I might play with it myself...

If someone made a boattail for a prius I'm sure that would get the business going.

Molding isn't too hard - just requires several pretty pennies of start up capitol

[UfoTofU]

Looks good basjoos!

I found this via Hack-A-Day actually.

[basjoos]

Originally Posted by Spyral

Wow, do you think I should do this to my GTO? I get about 26mpg on the highway and about 12mpg around town. Depending if I am on the gas or not. When I activate the nitrous oxide system I get even worse gas mileage. However, the car is very fast. I have no catalytic converters on it either.

The car looks great!
.

Cd reduction would work to improve the high speed performance of any car and is what they do on the Bonneville Salt Flats to increase the speeds of their speed record cars. Since aerodynamic drag is the dominant load factor at higher speeds, the faster you go, the more you'll notice the effects of a low Cd, reducing the amount of power you need to travel at that speed and in effect acting as the equivalent of a horsepower boost at the higher speed. As far as fuel efficiency goes, a low Cd extends the range of speeds where you can still get good fuel economy into the higher speed brackets and a low Cd car will get better fuel economy than an otherwise identical high Cd car at any speed above 30mph, the difference becoming more and more noticable the faster you travel.

[basjoos]

Based on what I saw in the road salt deposition patterns, the largest recirculating eddys remaining are those produced downwind of each rear wheel,so I built and installed a mini boattail behind each rear wheel.

[voxelman]

Basjoos,

You are an inspiration to us all!

[Coyote X]

Is there a deflector on the front of the rear wheels?

[MickF]

Basjoos - could you do some pics of how the radiator exit air leaves via the wheel wells? And how efficient is this (relatively) to bonnet vents? I know many of the recent Porsche 911 models vent the rad air into the rear wheel wells, but they appear to use shaped spokes on the rear wheels to act as a fan.

[Darxus]

Originally Posted by Coyote X

Is there a deflector on the front of the rear wheels?

No, better:

Originally Posted by basjoos

there are 2 side skirts on each side, one even with the inner edge of the tires, the other even with the outer edge of the tires

[basjoos]

The radiator air exits through the stock openings to the front wheel wells, which have the OEM wheels. The advantage of this method over bonnet vents is that I am dumping my radiator exhaust into an area that is already turbulent, so it isn't adding to the total amount of turbulent air created by the vehicle. But the air exhausted from bonnet vents, depending on how it is handled, could add turbulence to the car's airflow as it merges with it.

There are deflectors in front of the rear wheels in between the two side skirts. I started out with a wheel spoiler in front of each wheel using the spoiler design found on many hondas and toyotas that deflects the air downward in front of the wheel. I later replaced the front wheel spoiler with the current air splitter and added the side skirts, but left the rear spoilers in place to deflect any air that got up inside the side skirts before it encounters the rear wheel.

[MickF]

Originally Posted by basjoos

The radiator air exits through the stock openings to the front wheel wells, which have the OEM wheels. The advantage of this method over bonnet vents is that I am dumping my radiator exhaust into an area that is already turbulent, so it isn't adding to the total amount of turbulent air created by the vehicle. But the air exhausted from bonnet vents, depending on how it is handled, could add turbulence to the car's airflow as it merges with it."

So, is the air in the wheel wells at low pressure? That seems to be a contentious issue on the net, seeing as how many race cars have vents over/behind the front wheels to vent air from the wheel wells (although on some drag VW Beetles they put vents over/behind the wheels to stop the fenders from generating lift). I know the air in front of the tire is at high pressure, but I would assume the air behind the tire is at low pressure.

I'm trying to solve a cooling issue with my car (1971 Datsun 240Z with intercooled 6cyl 2lt turbo) due to horrific airflow issues with the engine bay. I can (and will) reduce the air entry through the radiator support panel, but I'm trying to work out how best to get the air out from the engine bay. The air past the turbo gets to ~ 230C, and heats the firewall & trans tunnel to ~ 70C which makes it rather uncomfortable in Summer.

I could use the trans tunnel as a duct to the rear wheel wells (undertray and with insulation on the tunnel to try and keep the heat out of the car) - not sure how well this would work. Or possibly duct from the engine bay to the front wheel wells (through or under the inner guards) with vents in the guards behind the wheels.

I'm also looked at the 2lt Super Touring cars - the ones I looked at (BMW RWD and some FWD's) had the air through two small radiators and then the outlet air is ducted to vents in the ends of the front spoiler (side of the body) ahead of the front wheels.