himself

Question: I'm going to add a bigger wing that should produce ~200 lbs of downforce at 100 MPH. [graph below]. Currently I'm running -2.8/-2.6 degrees of camber F/R. Zero toe up front, and .13 degrees in the rear.

Should I adjust alignment settings for the additional downforce? Or are my current settings OK regardless of the aero on the car?

Also, is there some general rule for downforce? (e.g., what would 100 lbs of downforce equate to in terms of grip or speed in a corner). Like 100 lbs of downforce will be about 5 MPH in a corner, or .1 G, etc.

Thanks,

-td

analogmike

I believe you should reword that as "200 pounds less lift at 100MPH". No need to change alignment, it will get closer to the static alignment the less lift you have.

Veloce Raptor

+1

Also consider whether you have enough front splitter for all this extra wing. If not, you may soon experience a bunch more understeer..especially at higher speeds.

Doc GTO

+1

Matt Romanowski

And it depends on the speeds in your corners. Big difference from a track like Lime Rock to Watkins Glen to Pocono Long.

kurt M

I change the AOA for VIR and Summit Point. Fast setting at SP is not the same at VIR.

Simple fix. Just go 200 MPH so the wing can do the most for you.

onefastviking

So many things to consider here when adding a wing.
From angle of attact, to drag, to alignment, to tracks driven, to tires used, gurney or no gurney (not really an option in my mind), still have all street rubber bushings or all race mono ball throughout. If you are adding a wing out back you had better be changing the front as well, or doing something different out in front to balance the car. It's also just not the wing you are adding but where that wing is that makes a difference, using early stock 996 uprights vs World Challenge 997 uprights makes a difference also.

IMHO, all of these items should be considered, balance front to rear probably being the most important, that keeps it drivable, and then all the rest taken into account, those make you faster.

ProCoach

^^This^^ THE holy grail...

Also, using data to tune wing AoA and for assistance in reaching a balanced setup is a must.

If you have shock pots or ride height sensors, use them to calculate tire loadings (and ride height change through velocity change), change in rake and splitter height. If you don't, use vMax and sector times in the slower stuff to reach the best trade-off.

You will not see any measurable difference in corners with vMin under 70-75 mph.

You will see an improvement (if you nail it down) in braking from terminal velocity which will also require you to alter the taper of your brake release.

Adding aero to a GT car is not the same as tuning a native aero formula or sports racing car. A lot of the stuff sold has no serious testing or data to support claims.

Good luck.

ProCoach

Hmm.

vMin at VIR T1, T4, Oak Tree and T14A is similar to Summit T1, T5 and T6.

VIR Climbing Esses can be similar to Summit T8-T9, if you come out of the Carousel quick enough.

VIR South Bend (T10) similar to Summit T3 and T10.

VIR T16-T17 similar to Summit T7-T8 in speed and importance.

In lower powered cars (doing 1:59-2:01 at VIR or 1:15-1:16 at Summit), vMax is similar between them but only once and for a very short time at Summit, so I would think you would run more AoA at Summit. I don't change it much, myself.

Trying to understand what you're saying.

onefastviking

One big warning I will give, adding a rear wing with the wrong tire and or tire pressure and especially when driving on a large banked track will add to tire loading causing tire failures at less then optimum times on track. Like there is really a good time to have a tire failure on track, right.

I'm just saying, consult with someone that truly knows and has experience and check your tires closely when adding your wing. From additional sidewall loading heat failures, to tire rub cutting the tire on inside or outside, you could have issues.

Veloce Raptor

Agree with this. IMO run a bunch of wing. the couple of MPH you may lose on a long straight is more than made up for my the extra MPH you gain in corners, especially fast sweeping ones.

himself

Sounds like this will be a fun experiment. I am primary concerned (now) with tuning at a macro level (drivability as Viking put it). Also, I don't have any relevant sensors other than G loading, speed traces, RPM and throttle. I'm pretty sure I have the cup splitter on my car already, but when this one "falls" off, I'll make sure I don't downgrade to the street version. [Q: should I adjust the rake of the car?]

As for vMax in corners on the tracks I drive primarily:

MSR-C (1.7 and 3.1) has a three ~80+ MPH corners/complexes (Big Bend, Boothill/Tombstone/Horseshoe, Ricochet). Nothing over 100 MPH. vMax on the straights is ~115-120 depending on direction.

MSR-H (CCW) has two 100 MPH corners (the Sweeper and Gut Check) and a carousel that is ~80+ MPH. A number of others in the 50-60 range. In the CW direction there is the Launch (70+ MPH, entry into Diamond's edge (90+) and the Carousel (~80+). vMax on the straights is ~130.

I don't get to TWS as much, and haven't even been there with the GT3 at all, so I have not real data for that track. I also haven't been back to ECR in years, but I think the wing would be neglible there as there is only 1 corner anywhere near 70+ MPH. I only have data from H2R for one event, and I won't likely run there to get data anytime in the near future.

My plan is to get the wing, set it at max attack (8 degrees) and see what happens. If the front starts to wash out and I can't overcome it with the bar, I'll drop the wing to 4 degrees. If it is still a bear, I'll drop to flat and then start adjusting the front aero to balance adding the rear back in.

But, given the limited number of high speed corners and the front splitter I already have, I"m hoping that the (macro) tuning won't really be that difficult - at least to make it driveable. After I get something workable, I may start to modify the front/back balance to see if I can get it fine tuned. When I get to this point, I'll enlist some help.

Do you bump air pressure when running a bigger wing?

As an alternative, I suppose I could update my LSD with a Guard unit instead of the wing. Only problem is that I can do the wing myself and get the swap done pretty quickly. LSD will require a shop with knowledge. Maybe I could enlist Viking [eventually I'll do both, but I'd like to do it in stages to collect data for each]

-td

KaiB

Were it me, I'd bite the bullet and install the Guard LSD now.

jrgordonsenior

Exactly. Rake is soooo important in these cars. Cups run 85mm front and 120mm rear a rake of 35mm. You can't get a street GT3 that low in front but 95mm is attainable and thats where mine is with 4" springs (same length as cups only 500 lbs). Also rear tire diameters affect rake too so if you switch rear tire diameters from your initial setting you should adjust your rear ride height accordingly....

jrgordonsenior

Minimal wing is better. I'd go the opposite way starting out almost flat and observing how the front end feels. The I'd increase the wing if the front end feels planted. As others have said, it's very track dependent. I run almost flat at high -speed tracks like Cal Speedway with 19 degree banking, and at most I run 4 degrees on flatter high speed track like WSIR. Wings can really slow down your lap times, but they can also make your car feel more planted at speed. It's a trade off, sort of like marriage....