I was wondering if I were to cover up the bottom of the frame with say, a 1/4 inch thich slab of abs plastic from the front bumper all the way to the rear bumper. Obiviously, there will be some heavy fabrication in molding the slab to cover pieces like the exhaust, tranny, etc, but nothing me and a buddy can't do. I just want to know if the results are worth the effort. Our E36's aren't exactly the most aerodynamic vehicles out there, and i figure that the smallest addition will make a big difference. Anyone advise against this, anyone think it's a good idea? Input is appreciated as i plan on starting this at the beggining of next week as a finishing touch to my christmas present to my car of coilover suspension, lsd, front and rear swaybarbarians, and front and rear spoiler:evil2

Are you racing or what?

Not Legal in any Class/Series.

ABS will deform from exhuast heat by the way.

If you have a $50k to dump on a day in a windtunnel, go for it.

A full flat bottom will help slightly, but only if you have something designed. Just bolting abs to the bottom of the car won't really do much, especially if its not racing at the extreme limits.

Spend your time on something more worthwhile, like driving the car on the track :)

If you have a $50k to dump on a day in a windtunnel, go for it.

A full flat bottom will help slightly, but only if you have something designed. Just bolting abs to the bottom of the car won't really do much, especially if its not racing at the extreme limits.



That's complete BS. You can get 90% the results of a "tweaked" setup with some general knowledge and intuition. It's that last little bit that's so hard to get and what all the "big boys" spend big $$$ to get that last little bit out.

Jacob, You really think he'll notice a difference, c'mon. Its probably a street car, that is driving at 40%, aero will not have any significant affect.

I agree 90%, if not more comes from existing data, and simple quick experiments/equations/models/etc. But, and this is nothing against him, i doubt he'll be doing anything to that affect.

Jacob, You really think he'll notice a difference, c'mon. Its probably a street car, that is driving at 40%, aero will not have any significant affect.

I agree 90%, if not more comes from existing data, and simple quick experiments/equations/models/etc. But, and this is nothing against him, i doubt he'll be doing anything to that affect.

I never said anything about noticeable effect. I'm sure it will make a difference above say 80-90mph, not a huge one if you keep the floorpan intact, but it'll make a difference.

The idea that you can't get a "good idea" without complex simulations, testing and crap like that is proposterous though. Good ingenuity is pretty darn close to what a simulation would give you on something as complex as this, and real life testing is much more accurate but EXTREMELY costly to get that last little bit out.

Regardless, do you really think he's going to come up with something worthwhile, let alone safe?

And this is nothing against him, but i checked his other posts...and he made a post to see if he could pay someone to write his college acceptance essay....

I'm done, bed time. Later Jacob

Hey. Thanks for your input. This is a forum and i use it only for giving and receiving info, i dont take anything personally so as long as your input is relevant and helpful, it's all good.
A friend of mine is in industrial design and has the resources to make a mold of this. I wouldn't waste my time and money in making something unless i did it right. I would obviously wrap the exhaust in a heatshild, and would mold the cover around the exhaust as well as every other piece that does not lay flush on the chassis. I have recently been going to the track, and this car could be quicker if it had a better shape and i figure all the air getting trapped under the car would be a start. I personally think it would make a big difference in speeds excess of 70, and would benefit the downforce slightly in not having air push up against the car. I was just hoping someone else did this and had something to say about it:)

Not many people since its illegal in all classes.

COuld be beneficial if done properly, but you'll be trapping a LOT of heat in, and there are a lot of safety risks. Plus you'd want a front/rear splitter/diffuser.

If I were you i would concentrate on the following before you worry about aero:
1. Driving skill
2. Suspension/tires
3. Driving Skill
4. Suspension/tires
100. Hp.

Top Mod cars in the country are going pretty fast with out this, and most likely are more skilled drivers and have more HP and better suspension/chassis setups.

You'll benefit most from spending your time on the other areas mentioned.

Just trying to be honest and save you time, and help you concentrate on what really matters. And Safety should be on the top of the list if you plan on tracking with any modification such as this.

Instead of wasting time w/ full underbody aero, work on the driver (you). Everybody could go faster and doing the full underbody is not the way to go. I understand you can do it right but its unnecessary for track days. Better tires, suspension, setup and most importantly the driver are what will make the car quicker.

Edit: steve beat me to it.........

Could it make a difference? Maybe, yes.

Is the outcome worth the effort in construction? Probably not.

But go knock yourself out if you want to, take pics and report back :D

Well, if it's not going to make a difference, i guess i won't do it.

Oh, also, i was going to use this as a finishing touch to my full suspension, lsd, swaybar addition. thanks for input, I'm convinced

Good call. And thats why this forum is good :)

Get your car light, and get as much seat time and instruction as you can.

Get suspension/chassis/tires set, and if you really think aero is the single factor holding you back from running lap records, THEN you should wrry about aero.

If you dive into aero without covering all aspects, you could potentially create more problems then you had before. Changes during dive/sqaut and other "disturbing" movements can be drastically affected by aero aids such as this.

Keep it simple, and develop the skill behind the wheel...thats the cheapest way to make your car faster.

Whats your suspension/swaybar/tire setup?

Oh, also, i was going to use this as a finishing touch to my full suspension, lsd, swaybar addition. thanks for input, I'm convinced

save the money and go with better tires and more track time

Hey man, i dont know alot about aerodynamics but this thread helped alot. I dont know if this would help you but Germanwerkz has this Front Bumper Aluminum under panel that looks pretty good.
Germanwerkz.com
Thats my .02 cents of advice. Oh and post some pics of those plans and if you go for it.

Yea, every CLub racer has a splitter like that.

Search for Posts by "bg m3" on "velocity splitter" that might be something you can bolt on and benefit from without calling F1 engineers to get your E36 to 240mph ;) Have fun bud.

I have two wheel/tire setups currently. THe one i use for my street driving (drive a little easier) are my BBS rk 17's with 225's in the front and 245's in the rear. Tires are michelin pilot sports. THe ones i use on the track are my doublespoke II's staggered with s03's. SUspension i will be going with is GC coilover (probably track school) but what i have been changing. UUC swaybarbarians in the front and back, (unless anyone has any other suggestionss). Limited slip diff 3.23 from my wrecked m3. I am slowly prepping my car for the turbo and this will be the second to last major step; next step is bbk. Then motor build and turbo. I am pretty happy with my rk's and tires.

As for this thread. It turned out to be very informative. Steve, i had some bitter feelings towards you from your early post, but you don't seem like the person you expressed yourself as. MUCH love BRotha:)

As for everyone elses input, i appreciate it. Plenty of time has and will continue on the track.

Oiy...turbo?

haha, its all joking aroun d man, don't take anything on the forum seriously...think of it like the jokes that go on in your family.

Have fun with the project.

i dont know if this was suggested, but maybe start by crafting a front splitter. especially if you are handy with some abs plastic.

If you're doing high speed runs on the bonneville salt flats, I'm sure it'd help. Other than that, probably not.

I have two wheel/tire setups currently. THe one i use for my street driving (drive a little easier) are my BBS rk 17's with 225's in the front and 245's in the rear. Tires are michelin pilot sports. THe ones i use on the track are my doublespoke II's staggered with s03's. SUspension i will be going with is GC coilover (probably track school) but what i have been changing. UUC swaybarbarians in the front and back, (unless anyone has any other suggestionss). Limited slip diff 3.23 from my wrecked m3. I am slowly prepping my car for the turbo and this will be the second to last major step; next step is bbk. Then motor build and turbo. I am pretty happy with my rk's and tires.

As for this thread. It turned out to be very informative. Steve, i had some bitter feelings towards you from your early post, but you don't seem like the person you expressed yourself as. MUCH love BRotha:)

As for everyone elses input, i appreciate it. Plenty of time has and will continue on the track.

I see tons of room for other small improvements. First step would be to understand what the sway bars do and how changing them will influence the rest of the suspension. Next is to get away from staggered wheels/tires.

I'm not quite sure what "prepping a car for turbo" involves... and all of my BMW's are turbocharged. :dunno

BBK is a waste. Especially on an occasionally tracked street car that even when on track is on street tires. If you can overwhelm the stock brake system with decent pads on street tires in a relatively stock car, you're doing something horribly horribly wrong.

I wouldn't worry at all about aero until you get EVERYTHING else sorted. So little to be gained there... and so much to be lost if you get it wrong. You are much more likely to induce *strange* high speed handling characteristics than you are to help with the balance of the car at any speed.

Suspension is likely the most important part of the setup. (It is if you are one who views the tires as part of the suspension... which is of course key.) if there is any part of the car to focus on "fixing", that'd be it.