Ive had some good dumpster diving days, but at the Sears World Challenge GT event, not only did i end up with another set of Toyo RA1s, but a 2006, Porsche 997 GT3cup car wing that had been damaged slightly in an accident beyond what the owner was willing to have fixed. For my uses, its perfect.

Here it is Im thinking its going to be more efficient than my 10degree turned down GTS wing, so if im getting 80lbs of downforce at 120mph, maybe ill be able to get this at 85 or 100mph . So, If im getting 60lbs vs 90lbs at 80mph, thats about 30lbs more down force. probalby at the cost of 10lbs of drag.
(since we have 12" radiused tires, thats at a cost of 10ft-lbs of torque at the wheels.
in 3rd gear with a 4.6:1 ratio, thats a little more than 2ft-lbs of engine torque lost. I think it will be a fair trade.

Anyway, let me know what you think. these are temp brackets to see if the wing would fit and could be mounted. the end plates are paper and will also be cut from 1/8 aluminum. now, ill take the templates to the fabricator and mount it up. nice to be able to test something adjustable on the race car. most everything is maxed out on the Holbert car, and havent had a need to soften anything up.



Mk

 

Mark,

I think your spot on in mounting the 996/997 cup car style wing to your car. I have long thought the profile of both the 928 and 996/997 cars are very similiar and those wings would be a benefit on the track. You know they work since Porsche has engineered them to help their cup cars.

Looks like you are placing the wing at about the same height as the 996/997 cup cars, that would be my only concern, would not want it too high above the roof which could give you unnecessary drag on long straights. Are the side plates the same size as the original ones? It looks real good too in my opinion.

Are you going to get fancy and cut "928" into the up-rights like they do for the cup cars where they say "GT3?" I know where there is a water jet cutter in Florida who can probably cut the end plates, up-rights and cut "928" into them. Templates would be needed to put them into a CAD file.

Constantine

 

Hey MK,

What the heck is going on? That looks just like a tow vehicle behind your race car!

 

If the new wing is too effective, and nothing is done to the front of the car to compensate, you may find the front-end pushing in the faster corners.

 

Cool - if painted red to match the car.

 

Mark, for racing the wing looks great. On another note, how did you get your rear quarters to flare like that?

 

Yea paint it red.

 

Who cares what it looks like as long as it works..it is a race car.

 

You might want to add a guerney flap or something similar in the lower part of the hatch to help avoid turbulence around the back.

The wing will probably work well, I would imagine that it needs to be mounted over the roof line to ensure that it gets undisturbed air.

 

Thanks you guys. Your all spot on and were reading my mind!

I was thinking about the drag issues and thanks to getting the old brain going with all the torque vs hp discussions, calcualted that if i gain the increased downforce over the "tilted" stock wing, the drag in ft-lbs would be a pretty low percentage of the total torque to the wheel. (and easy to calculate as our wheels are 1" radius)

nice though about the hight. i was thinking mainly of looks, but i think you are right about unessesary drag on the straights if too high

The winglets were designed in proportion to several shapes i liked. the new 997gt3cup for example, with some subtle changes based on what ive seen on speedgt.

painted? absolutely its a plan. probably the uprights will be aluminum, but maybe those should be painted too???

etch the "928" in the uprights??? good idea if the wing proves to work, and it doesnt cost too much. i thin the winglet etched with 928 would be cool too.

thanks again,

any other comments

Mk

 

That's what i was thinking too. I know Don Hanson did a little carbon fiber flap down there, like the early S models. I wonder how much that helps in drag reduction by breaking up the laminar flow off the rear? the old GTS wing was low enough where it probably did some of that from the air coming off the roof and down.

another good observation. Thanks.

Mk

 

another great point. I have a pretty good splitter (also from a gt3 cup car from 2000, given to me from hanson who modified it for the 928) I have as much splitter as most of the cars that have had wind tunnel work and are top competing cars, so i should be ok. however, the car does push in the slow turns and down the radical 180 degree turns like the carrocel, it pushes slightly. But, if i could get on the gas earlier, i could be faster and drive around it. even out of the carocel, its scarry tail happy on the exit, but not bad as long as my garbage can Toyo RA1s are good. hoosiers that are old are down right scarry there!

MK

 

Not to pick on you Perry, but this mentality really bugs me. Why shouldn't race cars look good? I take a lot of prid in the fact that my track car is in as good - if not better shape overall than my street car.

I dunno, when I see some beat up POS parked in the pits at some events, I really wonder just how safe or mechanically solid the car is. Again, not picking on you, I hear this all the time at track events "who cares it's just a track car".

 

I found this interesting...."Wind tunnel development of the Joest Porsche 962C was carried out at the Porsche Weissach tunnel (full scale fixed-floor with boundary layer suction). According Ralf Jüttner, Technical Director for Joest Racing, maximum downforce for the Joest 962 was 5584 lbs. for 1396 lbs. drag (max L/D: 5281 lbs. downforce for 1200 lbs. drag). Jüttner also mentioned that, "In general, I think we were quite far off the downforce values of the Nissan and the Toyota. Anyway, I do know that downforce figures from the Weissach tunnel showed smaller values compared to other tunnels. But regardless, there was no way coming close to the Toyota as we could personally see large differences in the braking points for the first chicane at Portland for example." That would sem to imply that for that car they got about 4 to 1 in down force over increased drag BUT they had horsepower to BURN !

 

That is interesting. generally, many wings alone have about a 3-4:1 ratio of lift to drag. interesting that the entire car, including wings and ground effects, had a 4:1 ratio. (wonder if there is a NACA number for an entire car shape, ha ha)

anyway, i think the trade off for the GT3 wing on my car, would be worth the few ft-lbs of lost force. got to figure id be gaining a MPH or two increased down the carocell at sears or the kink (turn 6) at Laguna. If this takes 50lbs more down force, the increased drag would only be in the 15lb range. as i mentioned, though 3rd gear ratios, that would only be in the 5ft-lb engine torque range, right? (wonder if im missing something here) and much less at any of the lower speeds. (but so would the downforce).

MK