E30 Aero

#16

Ranger wrote:

Isn’t that why we race? :laugh: It took me riding with Skeen at Roebling to truly understand just how far you can hang the back end out on an E30. His typical slip angle in Turn 3? (the left hand sweeper) at Roebling is the same slip angle at which a Miata is “way past catch-able.”

Brake earlier and lighter and the trail braking is easier.

My $0.02 on T1 and T12 at Road Atlanta? You have enough compression aiding traction in those two turns that additional downforce won’t even be felt. The tricky part in T1 is getting the car across the crest at the centerline of the front straight. Once you crest that hill, the car picks up traction. Except with wet grass, there reall is a lot of run-off room up the hill if you get it wrong.

[quote]
Re. CMP. I don’t think that there’s anything magical about the kink that induces over-steer. I agree that over-steer is common there, but maybe it’s cause by people being light on the throttle as they ride the bump and then try to get the car to settle again.[/quote]
I usually see throttle-on oversteer there. I stay on the gas until I hit the bump, then feather it if the back end is getting wiggly. YMMV.

#17

Steve D wrote:

[quote]
MidOhio - Undecided. The Keyhole and caroussel are probably too slow for a splitter to help. Can you go through Turn 1 flat? I have always had to brake a bit to set the nose.[/quote]

You have to brake for turn 1, a splitter might help here as I have had the front end wash out on me in turn 1 but usually its the back end that wants to step out first. A splitter might help in the fast left hander coming out of thunder valley. Maybe it would help some at the exit of the keyhole because it understeers badly there but like you said I’m not sure you have enough speed, probably can’t hurt. Also I don’t run the rear spoiler as mine is a 325i, I doubt it does anything much.

#18

Steve D wrote:

I’d contend that additional traction due to compression is brief. Brief compression, then rebound takes the traction away, and then it settles into steady state. I’d call the period of added compression only about 1sec.

So you get a second of better traction at turn 12 turn-in and at turn 1 just past the apex. Sure, there’s lots of track out width at the exit of turn 1, but the outer 2-3’ of track is all marbles. So that track out width is there for you…as long as you don’t ask too much of it.

#19

Steve D wrote:

[quote]Ranger wrote:

VIR - Undecided. Esses and South Bend would be nice with a splitter, but that place is pretty rough if you leave the surface.
[/quote]

Ditto. My first time at VIR my airdam ended up at the corner worker’s station at Turn 5. Without the car.

I did ask my computational fluid dynamics guys about aero for a 325is. What do you suppose they meant by “You’re better off with a brick.”?

#20

Sounds like he graduated from Georgia Tech. :wink:

#21

Update:

I think a splitter is almost worthless on an early model car because of the rules and big-ass bumper. Scott’s conjecture on the early model bumper:

  1. It helps to create high pressure zone on top of the hood. This reduces the lower pressure are on top of the hood and therefore reduces lift.

  2. It helps create a high pressure zone below it. This causes lift.

  3. It reduces the utility of a splitter. The splitter is supposed to help contain the high pressure zone that reduces the lift in point 1 above. But the bumper already does that. In order to contribute a splitter would have to stick out farther then the bumper and the rules prevent that. In fact, the rules make the bumper stick out ~ 2" farther then what a splitter could.

The way the rules restrict early model splitters, it’d be a challenge to do anything useful with one. The air dam would have to be far behind the bumper and then the splitter could stick out a couple inches. That would help create a barrier between the high pressure zone below the bumper and the low pressure zone we’re trying to create under the undertray.

Undertray. The current undertray scheme is one that allows about 1.25" of vertical travel. That way if it gets hit, it will have a chance to lift up a bit and maybe not get torn off. The vertical travel will be spring loaded so that it won’t be tempted to bang around under the car.

No really. Spring loaded.

The low pressure zone pulling down on the undertray should keep it all the way down under most circumstances I figure, but I think that this spring idea might work.

#22

Scott, Holy Toledo, here we go again. Where does this stuff come from? I assume this is conjecture? What role do you suppose the windshield plays in scenerio number 1?

#23

Ranger wrote:

Bingo. Small bumpers FTW.

Given the lack of side skirts, you can’t create a low pressure zone under an E30. The best you can hope for is to clean up the airflow under the car (at atmospheric pressure). I believe you can gain a bit of high pressure with the splitter, but as much as anything you are trying to prevent the tumbling of air down under the front when it hits the blunt nose of the E30.

You have got to be $h!tt!ng me. Are you high?

Here. I’ll save you some trouble.

9.3.13.5. Modifications to the underside of the vehicle for the purpose of improving aerodynamics are not allowed.
9.3.13.6. Engine under-tray panels may be removed.

Note that 9.3.13.6 doesn’t say “…may be replaced.”

You can install a splitter to smooth airflow under the car, but if it isn’t a splitter, it is an under-tray. Which is illegal. I love me some rules interpretin’! :laugh:

#24

Stevie D, big bumpers rule.
Big bumper drafting trumps little bumper clownforce any day.

RP

#25

Hmm. My response got lost. Cliffnotes:

It’s not illegal. The undertray can extend back to the front of the fender wheel arch. Since the current plan has it not extending forward of the air dam, I don’t think that I should be calling it a splitter.

We’ll have to see how this spring idea works. If it seems pretty secure, fine. If it’s wiggly, then it will go away.

Re. what role do you suppose the front windshield plays? I assume that this is sarcasm. Based on a couple nights research I’m giving you good info. If you want to throw rocks, do your own research. If you are curious for more details, bring the subject up at CMP.

#26

Ranger wrote:

[quote]Hmm. My response got lost. Cliffnotes:

It’s not illegal. The undertray can extend back to the front of the fender wheel arch. Since the current plan has it not extending forward of the air dam, I don’t think that I should be calling it a splitter.

We’ll have to see how this spring idea works. If it seems pretty secure, fine. If it’s wiggly, then it will go away.

Re. what role do you suppose the front windshield plays? I assume that this is sarcasm. Based on a couple nights research I’m giving you good info. If you want to throw rocks, do your own research. If you are curious for more details, bring the subject up at CMP.[/quote]

Rules aside: If you are talking about coil springs on the fasteners then save your time and just know it’s be “wiggly”. Sure, you could over ninjaneer it ( and you are the man for the job), but a leaf type spring may be a better option?

#27

scottmc wrote:

[quote]
Rules aside: If you are talking about coil springs on the fasteners then save your time and just know it’s be “wiggly”. Sure, you could over ninjaneer it ( and you are the man for the job), but a leaf type spring may be a better option?[/quote]

Hey, that’s a great idea. Hmmmm . Spring steel…where to find spring steel. Run them longitudinally so they will withstand significant longitunal blows. Ya, this could work.

#28

And I thought this thread was going somewhere. I guess that’s the beauty of racing our cars.
Besides the fact they assured my idea of using that black plastic gardening edging as a dam, the rest is just talk.
Where did you guys buy the abs plastic from?
The guys from Top Gear used wood instead of plastic.

#29

I bought a roll of plastic from Speedway Motors. I’m leaning towards wood for the undertray. Finding other materials turned out to be a pita in a small town.

#30

I talked to the Honda Challenge guys who built a spec e30 in Norcal (Lock bros) about splitter construction. They use hdpe for the splitter, and abs for the dam portion. The theory being that the abs will give way and the hdpe will come off in 1 possibly reusable piece. Another common material, aside from wood, is alumalite (corrugated aluminum used in the sign industry).

#31

BETO wrote:

[quote]And I thought this thread was going somewhere. I guess that’s the beauty of racing our cars.
Besides the fact they assured my idea of using that black plastic gardening edging as a dam, the rest is just talk.
Where did you guys buy the abs plastic from?
The guys from Top Gear used wood instead of plastic.[/quote]

McMaster-Carr is a great source for just about any material you need.

http://www.mcmaster.com/

#32

My .02 cents.

Front Air Dam/Splitter/Undertray can serve several purposes even in a toolbox like the E30.

  1. Direct air where you want it, Cooling of fluids, oil, Engine coolent, Brakes.
    1b. Undertray also helps with this, getting air to move through the radiators. (Ex: In an E36 M3 at Buttonwillow, on a 90 degree day, Engine and oil tempatures run 10-20 degrees higher when the factory plastics undertrays are removed. Although no difference in front grip was detected.)

  2. Reduce lift at high speeds. probably does not create downforce, but any reduction in lift is welcomed.

The Lock Brothers built a very nice, robust Air Dam/Splitter. It is on the car we bought from them (former #25, now #55). We did not run it at our first weekend at ThunderHill as we were worried about an off destroying it and taking the Oil Pan with it. We are just finishing our Provisionals and figured getting around the track safely, without incident, was our #1 priority.

I have raised the splitter up from Mike Locks original mounting position for worry of catching it. I do worry the Lower Plexiglass splitter could catch and swing up into the Oilpan cracking it. In my short career I have already seen two Oilpans break. I think that is why the Factory E36 Undertray is built from such flimsy plastic and just shreds.

IF we could run side skirts and then put the splitter on the ground like NASCAR, then we would begin to create some significant downforce but again only at the highest speeds we reach.

In conclusion it appears to me the fastest guys remain the fastest because of their ability, skill, talent, and coaching. Guys like Donny Edwards and Skeen will continue to win even in cars down on horspower. Another guy out here, SN, runs in the front despite many in the field having 20% more Horsepower. Clearly the Nut behind the wheel needs the most work.

As far as rules go, I do think that the Splitter should be able to be the same on all the Spec E30s, the older cars should not be penalized compared to the newer ones just becuase the bumper looks different. And I do have the newer bumpers. So if the rule stays the same I am OK, but I don’t think it is fair if you are trying to keep these cars equal. Although it may not matter anyway.

Cheers,

Shoe

#33

I’ve been working a lot on various splitter/undertray ideas. I burned thru a lot of material and hours, and eventually had to settle for something I wasn’t particularly happy with because I ran out of plastic.

There’s a couple challenges that you will face when you are playing with this idea.

  1. You will want a design that is nice and light, yet fastens securely. But at the same time can be easily removed. Fastening the splitter to the air dam is easy enough, for example, but doing it in such away that you could easily separate the two is not so easy.

  2. The design needs to be flexible enough that it can take pretty good hits and bounce right back to shape. Yet at the same time to be stiff enough to do it’s job.

I ended up using 1/8" sheet plastic and thin plywood. But if you try this, get more then 20 sq ft of plastic because that’s only enough for 2 ideas, not 4.

The good news is that air dam and splitter design does allow itself to be torn off with out ruining the air dam.

The bad news is that I just tore it off. Sigh.

The air dam survived except for a brake duct. The spitter/undertray got a little beat up tho. It wouldn’t take too much to fix it, but since I don’t particularly like the design I ended up with, I’ll let it go until I feel the need for another project. Call it next week.

Today is dyno day to test the various things I replaced since my last, not terrific, dyno day. I was putting the car on the trailer and instead of getting on one of the rams, the car pushed the ramp back into it’s recess in the trailer.

It was kinda funny, in a sad sort of way, to see my air dam tear off intact idea tested after only 100 meters of life.

Shit.

#34

Ranger wrote:

I think we just came up with the title for your blog.

Sorry to hear about the demise of your splitter. I got through my timing belt project on the E30, but since I have the 911 up on jack stands for a coilpackectomy, I will continue to refrain from poking fun.

#35

I’m going to have to create something that prevents the trailer’s ramps from moving back in their recesses once deployed.

I’m about to order more sheet plastic. If someone wants some I can order a larger size roll and bring it to CMP. 1/8", black, 22" wide. Cost you $2/ft to play.