proper aero mods
 

most of you know what my 1303 looks like and what i do with it.
looking at getting some more downforce and better aero mods on the car.
at the moment i run a small front spoiler and a F3 lola rear wing, but no side skirts or flat floor and no rear defuser.
thinking along the lines of a deeper front spoiler with a splitter into a flat floor running into a rear defuser with some side skirts.
also i am going to mount the F3 wing lower and further back with mounts going to the frame horns rather than mounted on the flexable body which it is now, it has bent the panel under the rear window so i know its doing somthing
max speed is around 100/110mph and most of the time its spends it's time around 60/70 mph so i know the areo parts need to be quite big to work at these speeds.
any ideas and proven mods that work?

I've got a hankering to see how these sort of things work, they are affixed to basically any proper race car, but that being said, I'm not sure our cars see the speeds that make these most useful.

http://images.thesamba.com/vw/gallery/pix/841524.jpg

Jason

this is the front end of my car and the dive planes do seem to do something, well if the pulled rivets holding them on with are anything to go by the air is pushing on them quite hard. weather there doing anything aero wise is yet to be seen.
https://fbcdn-sphotos-a.akamaihd.net..._2575319_n.jpg

your rear wings look much wider than they need to be, narrower would reduce drag!

yep front and rear wings i have replacments that are not as wide, the front is still on the 25mm spacers so i cna narrow the front track and the new wings still cover the wheels. just got to make some moulds up so i can make some nice light ones.
car can also come down about 40mm as the new wheels make it sit higher so that shopuld help as well.
have the alloy sheet to make the spliter and flat floor so thats the next project. also have a new header which comes forward alongside the gearbox so the silencer can sit on top of the gearbox with the exit just in front of the rear wheel,allowing me to have a defuser.
got a few more things to do to try and get the wieght down but theres not a lot in the car anyway.

Check the rules for your front splitter protrusion allowance and follow it. For me it's 4" in front of the bumper (using a plum to mark the ground plane from the leading edge of the bumper) and I follow 4" ahead of the bumper all the way around. Having the splitter farther in front of the car and more importantly ahead of the bumper, forces more air to go around or over the car instead of under. The biggest mistake people make on the front splitter is making it too small. The second biggest mistake people make is not treating the splitter like a disposable part, (they will be if you're driving hard enough and the splitter's installed at the right height) so take that into account when you make yours. A good splitter can generate nearly 200 lbs of down force, so if you can stand on it, you've built it strong enough.

Side skirts should come as close to the ground as possible and on bugs should be somewhat triangular. The front of the running board/side skirt should go down to the ground next to the body and the trailing edge of the front fender and make a wedge to the rear so that it goes down to the ground at the outside leading edge of the rear fender. That will keep air from piling up in front of the rear wheel. Check out the side skirts on the Jeffery's J/sports racer for a great example.

A rear diffuser is great if you run a tight suspension setup (read: heavy springs) because the diffuser strakes need to be close to the ground. Also, the diffuser should not be much greater than 7* angle from the ground plane or you get flow separation. Ideally, you want to start the diffuser as far forward as possible to generate the maximum amount of downforce but again, there are usually rules stipulating where the diffuser can start (typically rear wheel centerline). A good diffuser setup can generate many hundreds of lbs. of downforce depending on it's size and efficiency.

Once you have all the aero in place and tuned you can nearly double your spring rate from your non-aero enhanced setup. It should come as no surprise that some mod class cars double their weight in aero at 100mph. A lot of my knowledge comes from mod cars and world challenge race teams for both low speed, high downforce and high speed, high down force.

i can come out 150mm from the plan view of the car but i dont run a front bumper. the class i run in has no rules reguarding underbody areo mods so i as long as i keep the 40mm ground clareance i'm ok. wont be going to hard on the spring rate as the tracks i run on can be quite bumpy and have a lot of camber on them so i need the suspension travel to keep the wheels on the ground.
a lot of the parts on the J-sport car are very well thought out and some thing simerler to there side skirts will be going on the car.