Downforce needed - battle of the craptastic eBay wings

[Jables]

something like this
http://dtmfiberwerkz.com/access/styl...ler-p-115.html

[BlackbirdM3]

Originally Posted by CorvallisBMW

Oh I understand what made the M3 great, but this is a $500 racecar not a $500,000 factory-backed touring car. We don't have the $ to graft on an entire M3 rear end. Hell we don't even have a back window. Some things can be easily done, like leveling out the rear shelf to be even with the trunk lid, adding some small vertical fins to help smooth/direct airflow and adding a wing/spoiler, but beyond that we're risking so many penalty laps (ya, all this stuff counts) that it would be totally counterproductive.

Like I said. wing vs spoiler. That's really all I care about.

I know about the cost cap. No you don't have to replicate the M3, just get creative and do something sort of like it. The principles work, just get it sort of close and call it good. Who cares if it looks good. It just needs to more or less work.

Will

[e30bulldog]

hey just saw this thread and I figured I would give my 2 cents. The so called "ricer" wings are actually wings (not saying if they work or not) and the "NASCAR" style wings are not wings at all and they DO NOT add downforce what so ever. They are spoilers, spoilers actually reduce drag and add stability under breaking or transitions. They can be very helpful in a high speed slalom where the rear of the car keeps walking around.

Honestly I don't think your car needs "down force" to keep the back down. What kind of tires are you running? You said you added adjustable rear tabs to align it better, so what is your rear toe and camber???

[CorvallisBMW]

Originally Posted by e30bulldog

hey just saw this thread and I figured I would give my 2 cents. The so called "ricer" wings are actually wings (not saying if they work or not) and the "NASCAR" style wings are not wings at all and they DO NOT add downforce what so ever. They are spoilers, spoilers actually reduce drag and add stability under breaking or transitions. They can be very helpful in a high speed slalom where the rear of the car keeps walking around.

Honestly I don't think your car needs "down force" to keep the back down. What kind of tires are you running? You said you added adjustable rear tabs to align it better, so what is your rear toe and camber???

Thanks for the tip! It's stuff like that that I'm really looking for.

Tires are Star Specs, same as 80% of the teams out there. We'll add rear adjusters before the next race, they're not on yet though

[NigelStu]

Originally Posted by e30bulldog

hey just saw this thread and I figured I would give my 2 cents. The so called "ricer" wings are actually wings (not saying if they work or not) and the "NASCAR" style wings are not wings at all and they DO NOT add downforce what so ever. They are spoilers, spoilers actually reduce drag and add stability under breaking or transitions. They can be very helpful in a high speed slalom where the rear of the car keeps walking around.

Actually that is only partially correct.

Spoilers like those in NASCAR do create downforce. They just go about it differently than a wing. Wing creates the downforce with a pressure differential between the bottom side and top side of the wing element. Spoilers create downforce by creating a high-pressure zone on the body in front of the spoiler. This downforce that a spoiler creates is what provides the stability you mentioned. Drag reduction (or increase) depends on size, angle and shape of the spoiler.


There are efficiency, max down-force and drag differences between wings and spoilers, with properly designed wings (airfoil shape) generally providing more downforce with a greater increase in drag.


The important aspect of both is that then need good (laminar) airflow to work properly. Hence the first step would be getting some rear windows in the car.



Corvallis - Do you guys have any extra body panels (from donor cars, or stuff you removed from the car) that you can re-purpose as a spoiler? Re-using parts like that is free per the rules, no impact on AIV. Trunk lid, hood, whatever you cut out of the trunk floor, inner door metal, etc.

[e30bulldog]

How much tread do u have left on your star specs, those tires are bad about heat cycling out before the wear mark. I have had many sets on my e30, having back tires like this makes the car undrivable.

Also.... How old are your tires???

[CorvallisBMW]

Originally Posted by NigelStu

Actually that is only partially correct.

Spoilers like those in NASCAR do create downforce. They just go about it differently than a wing. Wing creates the downforce with a pressure differential between the bottom side and top side of the wing element. Spoilers create downforce by creating a high-pressure zone on the body in front of the spoiler. This downforce that a spoiler creates is what provides the stability you mentioned. Drag reduction (or increase) depends on size, angle and shape of the spoiler.


There are efficiency, max down-force and drag differences between wings and spoilers, with properly designed wings (airfoil shape) generally providing more downforce with a greater increase in drag.


The important aspect of both is that then need good (laminar) airflow to work properly. Hence the first step would be getting some rear windows in the car.



Corvallis - Do you guys have any extra body panels (from donor cars, or stuff you removed from the car) that you can re-purpose as a spoiler? Re-using parts like that is free per the rules, no impact on AIV. Trunk lid, hood, whatever you cut out of the trunk floor, inner door metal, etc.

Excellent info!

We have plenty of old sheet metal around we could work in to a usable spoiler. Wings would be a bit harder but still doable.

Originally Posted by e30bulldog

How much tread do u have left on your star specs, those tires are bad about heat cycling out before the wear mark. I have had many sets on my e30, having back tires like this makes the car undrivable.

Also.... How old are your tires???

The tires were brand new in our last race.

[e30bulldog]

thats crazy! I have personally used those tires and its nothing like you described. This is very unlikely but I got a bad set of hankook rs-2's from Tire Rack one time...and they where useless. My e30 probably puts down similar power as that old m30 and I have never had that problem and I figured it would be less on an open road coarse.

What was the temp outside...I know my rs3's are useless at near freezing

[CorvallisBMW]

About 50F and raining. Remember though that we've added weight to the front and taken out a ton of weight from the rear. Couple that with bad geometry from lowering and, well....

[dinanm3atl]

Also consider 205s is the widest 15... assuming you are running 15s with the star specs.

[CorvallisBMW]

195/60r14 on bottlecaps

[dinanm3atl]

Yah. Well that is part of the problem. No weight in the back. More torque. Little rubber. Add in a wet track and asking for traction issues out of the corners.

[irish44j]

quick related question: is there any advantage to having a diffuser/small spoiler at the top of the back glass/back of the roof WITHOUT a trunk spoiler/wing?

just curious.

[NigelStu]

Originally Posted by irish44j

quick related question: is there any advantage to having a diffuser/small spoiler at the top of the back glass/back of the roof WITHOUT a trunk spoiler/wing?

just curious.

If it is done right, it should reduce drag and potentially reduce high-speed lift.

[irish44j]

both of those things would be good for a 2300lb e30 sitting on tall springs with a total lack of power. Because I do want to do some trackdays in the rally-mobile

by "right" what would you suggest?