Aerodynamics for sprints, hillclimbs and drag racing

[Jimster]

Hi this is my first post here, got recommended by a few people, who say this forum is probably one of the best for technical aspects for motorsport.

I would appreciate your help, this is not F1 related, but it's technical and involves cars.

My question is, what aerodynamic modifications would you make to this car if there's no rules stopping you?

http://rpmedia.ask.com/ts?u=/wikipedia/ ... L_1998.jpg

You can add, remove or modify to improve the cars drag, and/or increase downforce.

Can you describe the modifications, how they work and how effective they may be, you can use diagrams to explain too.

I'm mainly looking at endplates, splitters, diffusers, rear wings, spoilers etc.

Thanks!

[AlpineF1]

Well you would definitely need fatter slick tyres (depending on circuit speed) but i would imagine downforce would be a key area I would say before putting on all of the aerodynamic components you will have to lighten up the car (racing seats, aftermarket rims etc) and (for a twisty track with bumps) more toe in but only a little as you still want feel in the car. Welcome to the forum

[Jimster]

Well you would definitely need fatter slick tyres (depending on circuit speed) but i would imagine downforce would be a key area I would say before putting on all of the aerodynamic components you will have to lighten up the car (racing seats, aftermarket rims etc) and (for a twisty track with bumps) more toe in but only a little as you still want feel in the car. Welcome to the forum

Thanks for your reply and for your warm welcome

Wouldn't slick tyres be "mechanical" rather than aerodynamical?

Also, this might be asking a little too much, can you go into more detail and more specific? [-o<

[AlpineF1]

Well what do you want to know more about? and yes it would be mechanical but remember in a hillclimb mechanical grip is as important as aero dynamical grip
could you list some parts for me to explain how they work?

[Jimster]

Well I need 11 modifications.

Starting from the front to the back.

I can add things, remove them or modify them to improve the Cd (drag coefficient) and/or increase down force.

Considering I am quite useless at this, all I've came up with, is removing the windshield, covering the tyres, removing the mirrors, and adding a roof. And I can't come up with reasonable explanations for them, which I must do.

So if you can come up with some aerodynamic modifications, (or add and remove things) I'll be grateful.

Thanks for your responses so far.
Appreciate it.

[AlpineF1]

Well a spoiler to be added but not too big as i think it could upset some of the balance, a splitter, yes removing the windscreen and mirrors will work you can add a bodykit, i have some good reading for you this helped me alot when i was trying to learn about aerodynamics http://www.ara.bme.hu/oktatas/letolt/Ve ... erodyn.pdf

[Lycoming]

why would you remove the windshield, then add a roof?

[AlpineF1]

I think it would let more air to the back of the car but not much but it has to be either that or roof, in my opinion the roof option will add drag as more air would be in contact with the car

[Jimster]

Thanks very much, I will have a look through it tomorrow.

You've been very helpful, thanks for that.

[AlpineF1]

Thank you its no problem, are you actually racing in a hillclimb event or was this just out of curiosity if so i could help out with car setups if you want

[Steven]

You might want to have a look at the car's floor, and see how you can improve airflow thereabouts. I would think a flat floor will help you, along with a diffuser at the rear. To get this to work, you will need to look into lowering the car or fit your new floor so that it's close enough to the ground..

Another thing perhaps useful is removing useless grills in the bodywork which are there just for styling reasons. Either close some holes if the engine is cool enough, or just open up the current grills to get better airflow to the radiator.

[wesley123]

The biggest gains you can make at the moment is simply by stripping the car and getting out unnecesary weight. I think you can easily lose 50kg's and by that already improve pace a lot.

You can go aroudn and add a huge splitter, huge rear wing and gain a ton of downforce, but the rest of the car is not built for it, and will only cause you problems. What you gain in aero, also has to gain on other grounds, for example better tyres, different suspension, more powerful engine.

[amc]

If you're talking specifically about aerodynamics then there are plenty of things you can do, but in reality taking off weight is the best way to make the car faster.

Personally I'd put a sharp 'tail' on the back which could be incorporated into a diffuser, and don't forget the little things: taping over the panel gaps.

If you take off the windscreen you may as well take out the passenger seat and headrest and cover over that side of the cockpit. I'd then put a fairing behind the driver's headrest (a la D-type jag). If you do anything to the windscreen or headrests though you will need to put in a roll cage (unless you're suicidal) which will quickly take away the positive effects of removing the windscreen. Instead I would keep it and run with the roof and windows up, but fillet the join between bonnet and screen where you get a load of drag.

There's no need to even attempt ground effect - that's just an accident waiting to happen, and at your speeds and in your disciplines downforce is almost irrelevant. With a really well designed spoiler on the back you might get 100N of downforce in a slow corner. A paving slab in the boot creates less drag for the same handling effect. In fact better - because it will aid traction.

[olefud]

Your inquiry is a bit difficult in that aero is not the modification that comes to mind for the low speed events listed –though I admit to being a bit unsure as to what sprints comprise. Each competition has its own unique needs. For instance, reducing weight and getting the remaining weight up and back are the prime consideration for drag racing. For the power apparently available, aiding down force with increased drag would be a poor tradeoff. Traction off the line where passive aero is inoperative is the prime drag race requirement.

Removing the windshield and adding a tonneau cover are the easiest and most effective changes that come to mind.

[strad]

First aero thing ya gotta do is lower it.
Eibach no doubt make a kit and it would improve the body roll and improve the mechanical grip at the same time.
Get rid of the front plate mount...get rid of the driving lights and replace with ducting...preferably to the brakes..chop the windscreen and rake it back a few degrees...replace those huge outside rear views with something smaller and aerodynamically slicker remove that little badge and smooth it with filler and the same for those louvers if they aren't real and the BMW badge...take all those body seams and smooth them out with filler. Remove that top that's all bunched up and catching air if you're not going to run top up..better yet get a removable hardtop. Then research some side skirts and wheels that don't bite into the air so bad