Ok so i've seen these things in a few magazines and web sites ive search through. Do these things actually work? I've seen them on rx-7's and supras and such and claim to reduce drag....but the ones im talking about go on your rear bumper...it looks pretty much like a piece of sheet metal with holes to reduce drag. I've search to try to find and answer but couldnt come up with crap. I dont see how that could help all that much...but maybe it does. Oh well. Thanks


Andrew

 

I must help a little by reducing the parachute effect of the rear bumper. You could just use a hole saw

 

Yea that's what i figured. lol i guess you could saw a hole too though.

 

that works but looks ghetto, get the underside of your bumper tinned shut if youre worried about drag, but not useful unkless building a drag car...

 

a better way of getting rid of the paracute effect (for a daily driver) would be to make covers for the open pocket area under-bumper. Kinda like making skid plates for the front, but these are just flat covers, light and they dont have to be durable ..just stiff enough to hold on and not flap with the turbulance.

I've researched underbody aerodynamics for a few months. There is a lot of **** out there that can be done instead of adding a rear spoiler.
A car with a perfectly flat bottom will generate enough downforce as long as you keep the front lip lower than the bottom line of the car, and rear bumper a little higher than the bottom line of the car.

Less pressure underneath the car than over the car, tends to pull the car toward the ground.

Ideally, you would want the air from the front dam to flow straight to the diffuser in the back ..to enhance this effect.
It is very difficult to route the air that way in a passenger car, or even to get the bottom flat! because of under-hanging exhaust, suspension, crossmembers, etc. The best thing we can do is to cover the "air pockets" underneath, and keep the front lip in great shape.

 

basically it is kinda a waste of time to try and develop your own diffusers and other underbody aero parts of your own since we dont have access to a wind tunnel.

i mean u can develop the stuff and try it but with with wind, and air pressure being a factor everytime that u go out to tune with will rarely have the same results. so you wont really know if u r making gains or losses. the only things that you can do and have realistic results are making simple things such as mentioned before like closing all gaps and holes that air can get trapped in and as a result cause resistence