mark kibort

I was able to enjoy of of the benifits of being an SCCA racer. They host a couple of free test and tune days during the year. Normally, i have nothing to really test, but since ive had the terrible handling issues because of adding the Cup car wing, i thought i would make a bunch of changes and go out and test out the new settings and theories.

All i can say is WINGs work and SO do SPLITTERS!! however, they must be well designed. I finished the small lip splitter and extended it out to near 4-5" overall. (equiped with dive planes on the edges). In fact, on the way to the track yesterday morning, the cable that holds the splitter up, broke and the wing tucked under the car, pretty heavily damaging it. I didnt have many of my spare parts that i usually bring to the races, but was able to do a road side repair over about 1.5 hours. got to the track near lunch time and still got 4 sessions in!

I vented the hood an verified visually and with the pressure sensor that a lot of air was now moving through it, instead of going under the car

Then, we took all the wing out, to 0 degree level, but of course found that we have a 9 degree setting by default due to air angled down from the roof line. We also measured near 260lbs of downforce at 120mph and 165lbs of downforce whereas the tilted stock wing would put down 80lbs of downforce at 10 degrees at 120mph 3x the downnforce, at much less tilt! The problem, orginally, was the 130-150lbs more downforce at 100mph would lift the front end by 50lbs. there is part of the drawback of a 6 degree cup car wing setting.

Now with 3 major things changed, we flattened the wing to 0, cut the hood and finished the splitter. The car handled really well. very turney, and the oversteer was completely gone. it had just enough oversteer to resemble the holbert car's old mannerisms. now, at thunderhill's very fast 80mph hairpin turn 2, i can throttle steer around it and with the wing's force, floor it at the exit! on my 2003 toy tires and in some traffic, i was able to click off a 2:01.8!! and many times equal to my best also in traffic.

Had a great time racing around with Mike Courtney in the SSF M3 ( 25hour thunderhill competitor) the great thing about the Holbert set up now, was that i could really run up on him entering many of the fast turns! I also was giving a TransAm Vet some trouble until we hit the straights. then i stayed close enough in the turney sections just to get my car oiled down. Those pure race cars are always a mess!

Not bad for all that fun at the track, for free!

if you dont mind the hole in the hood, it does work!

Mk

Ill see if i can post the fast lap with the M3 on YouTube or something.

Benton

Very cool, Mark. So the air coming through the radiator is venting through the hood? I might have to do something like that if you think it works... I don't know enough about these things to know if that works or not with regards to where the areas of high and low pressure are. I do know that my splitter will be shooting a ton of air up under the hood and through the radiator, so I would think something like what you have (similar to a GT2 or new GT3) would be very beneficial.

Mike Frye

***WARNING STUPID QUESTION ALERT***


Mark, I don't know anything about racing (but I like it and your updates), and only slightly more about aerodynamics, but would it be possible without adding too much extra weight to create some kind of way to adjust the wing while you're driving? (or have it change with the speed)

Sort of how several cars have a wing that only pops up over a certain speed?

I was thinking of a servo setup like on an RC plane except it would pivot the whole wing.

If this is stupid or against the rules, just ignore me and I'll go away.

***END OF STUPID QUESTION****

That's cool. I'd love to see it on Youtube.

Robert_H

Mark,

Regarding your splitters and spoiler up front, is this your own design or based on a commercially available unit that is heavily modified?

I've always thought that a combination like that would look very nice on the S4 (at the risk of getting it munched everytime I go into my driveway).

Your setup looks very nice and I am glad to hear that it works for you as well. Next season will be really fun for you and the beast. Good luck in the New Year!



Rob

mark kibort

Thats what a lot of folks were thinking and some doing in the 70s. However, dynamically adjustable wings and aero became a "no no". with the servo techology, you could really do some interesting things with this kind of design. however, then, it really would be about who had the most amount of computing power! So, it stand now that you get one aero set up and that has to work for all turns and straights.

one thing i have learned is there is realitively no trade off for the increased downforce. i still hit my max speed, yet i have 100 more lbs of downforce and who knows how much in the front. since wings have lift to drag ratios of 10-15:1 , at 100mph, in 3rd gear at a 4.5:1 ratio, 10lbs of drag would only be 2ft-lbs of torque at the engine!

Its not a stupid question. Its the first thing my aero engineer/pilot dad offered when he started seeing me paying attention to the aero stuff on the car!

Mk

mark kibort

Thanks Rob,

Yes, if you look closely, its classic my type of work (function before form )

However it is modeled after the Ferrari type dimensions for the splitter and dive plane, as well as many of the current ALMS, speed GT hood and worlds fastest sportscar hood designs, as well as our own 928 aero wind tunnel results showing the low pressure area, clearly in the lower front of the hood. (about wheel position ). i put tufts on the hood, and watched the strings point up at a 45degree angle, even at 120mph!! so, a lot of air is moving out of the hood now, instead of going under the car!

the rear wing is a genuine 2006 GT3 997 super cup car wing, (found in a garbage can at a world challenge race) the splitter was made from a '95 993 cup car splitter that Don Hanson used. it was about 1ft too narrow and it kind of defeated its purpose, as air would roll off the sides and still go under the car, instead of around it. by finishing it, it works like a charm! It just took me a while to believe that all this aero stuff was worth the effort and boy is it!

Mk

macreel

Good going Mark, always thinking & doing.

G'luck.

p.s. see a PM.

Fabio421

Whats the latest news on your new donated engine?

atb

Mark,

Are you running the stock belly pans?

mark kibort

But of course!

modified belly pans wouldnt be stock!

actually, i use the oil pan in the air stream as my oil cooler.

Mk

kjslider

Hey Mark,

You gonna be able to beat that 4 door, 4 cylinder mitsubishi this season?

perrys4

Does the air exiting the hood make a noticable difference in temp the engine runs?

mark kibort

Only if it loafs around after the first few laps of the race!

If we get that stroker bottomend installed, that 4 door, 4 cylinder, 28psi, 550hp mitsubishi will have its mirrors filled with a 21 year old stock, but stroked, 928! (even with used tires!)

Mk

mark kibort

That's a common misconception to a certain extent. The air entering the radiator vents underneath the car , unless you have a lot of belly pan coverage. what the hood vent does, is allow the air entering the radiator and some under the car, to vent to a lower pressure zone on top of the hood. (for downforce) im sure there could be some subtle gains in cooling efficiency, but i noticed none at t-hill. Most of the time, I run pretty normal temps, even on a 95 degree day, high humidity and WOT race conditions!

mk

mark kibort

Here is a little better picture. Plus, this is after ive repaired it from the drive up to thunderhill, where the entire splitter was almost under my car! all fixed up, JB welded, new aluminum and (3) 3/16" support wires.

also, a look at the rear holes that ive widened and covered with the same grill covering that i used on the hood. I was going to paint them black to match the color and size scheme of the stock black bumpers.

Mk