Aerodynamic Improvements for a... Jeep

Hello all, I'm brand new here. And well, yes. I'm trying something really weird. I'm attempting to build a '97 Jeep Wrangler (TJ) into a "racecar" I can take autocrossing. I'm aware that I'm trying to make a fish climb a tree.

Anyway... I plan on racing with the top and doors removed, losing about 300lbs up top. That's cool. Except for the fact that I then have a big, flat windshield with nothing behind it. I know it creates a lot a vacuum, along with the seats making the air turbulent behind them. I'm thinking of fabricating at least a flat cover to go over the trunk/bed area and eventually ditching the stock roll cage for a simple hoop behind the seats. Also, the big, flat moose side mirrors will be replaced with something a little less draggy.

I'd mainly just appreciate ideas on modifications I can make to reduce drag, and maybe improve downforce.

How much jeep is left in your end goal?

Some jeep: 

Not very much jeep (see article): 

I have this picture and probably very little else to add:

Can you fold your windshield down?  That should help with aero a bit.

With live axles at both ends, it might actually handle ok if you get it low enough and stiff enough.

At autocross speeds drag is not your biggest issue. Power and torque multiplication at autocross speeds make drag a third order (maybe second order for a Jeep) issue behind power and mechanical grip.

You could add downforce with any number of modifications, including spoilers, splitters, etc. keep in mind some of those require the car to be low and fairly stiffly sprung to work consistently.

In reply to stafford1500 :

I do plan on dropping it way further than it's supposed to but that's pretty far in the future. Right now I'm only lowering it a couple inches with some stiffer springs (luckily it's got coils, not leaf springs) But I was thinking of closing the gap between the bumper/skirts and the road with extended skirts and a fat, yet sturdy aluminum lip. Lots of gaps to close until I can completely Change up the suspension and really get it low.

Have you seen LSX Willy's?