Jickel180

Hey guys,

I'm planning out some mods for track duty after doing a few events with a completely stock 991.1 GT3 (well aside from a logger, race pads, and fluid). One thing I can't find is any data supporting improvements with adding canards up front and a Gurney flap in the rear. Now by principle I believe there should be some rear downforce improvement from adding the Gurney flap but I'm wondering if anyone has any Before vs. After data suggesting an improvement.

I know we won't find wind tunnel data on these parts so I'm asking you guys on your findings if they're of any noticeable benefit. Thanks for any help!

batmanm3

I think there was some CFD modeling by Versus (?) engineering over on the GT4 forum
That showed about 10lbs of downforce at speed (I can't remember exactly) , which leveraged from the distance of center of gravity, translated into actual downforce.
There was also modeling for the diffuser as well.

https://rennlist.com/forums/gt4/1103...s-canards.html

TRAKCAR

Can’t feel it, but back to back data shows little improvements.

qbix

It really does improve downforce. But you need to change for stiffer springs, too. Otherwise bottom will scratch on quick corners.

lnirenberg

OEM on track I found the car very unstable under hard braking from high speeds, the rear would shimmy left/right, it was very unsettling both physically and mentally. I added a Crawford wing, which I keep relatively flat to lessen drag, and problem immediately disappeared. Their wing comes with a short Gurney flap which, given the way I have the wing setup, must be the special sauce. My car is now track only so I'm not sure you'd want a wing like this on a street car but they mount to the OEM struts so its not inconceivable you could swap it in for track days.

FastLaneTurbo

Agreed!!!! The Crawford Wing eliminated the GT3's tail wagging under high-speed threshold braking, which was VERY disconcerting.
Difficult to know if the Gurney flap played any role. I've tried various Gurney Flap sizes, but frankly couldn't see much difference with
previous experimentation on my previous 993 GT2 Race Car. Apparently Dan Gurney did, so just accepted his findings as the
"secret sauce" and been grateful the wing worked as well as it did. If it was good enough for Max Crawford, certainly one of
the best Race Car Wing designers on the Planet, it was good enough for me.

mdrums

Gt3 rear wing is not adjustable, correct? I have a .2 GT3

erko1905

Are you guys doing anything in the front (different lip, canards etc) to balance out the Crawford wing in the back?

FastLaneTurbo

No, I never really found understeer to be much of a problem on either my GT3-1 or GT3-2 with the Crawford wing. Moderate Understeer
is a relatively slow motion event that is easily handled by increased trail braking while cornering with suitable steering adjustments.

Moderate Oversteer is also easily controlled with throttle but Snap oversteer is not. That is why I always prefer maximum
rear downforce to lock down the rear of the car. In racing, I've found a much larger, lower and stronger aluminum front splitter
extending 4-5 inches from the front of a 911 Body will reduce understeer enormously even with the largest Rear Wings.

Jickel180

Thanks guys. This helps a lot to know there's an improvement. I was a little apprehensive to tack these things on without any benefit. I'll explore the canards and Gurney combo for now, but I like the idea of the easily reverted Crawford and APR GTC-500 wing (at a later stage when I inevitably go off the rails).


It is, but we only get 1 adjustment. I believe the same is for the .2 GT3. The manual cautions about understeer when the wing is adjusted but I have yet to try it. I figured a Gurney added with no angle adjustment should yield "free" downforce with a minimal drag penalty.

GrantG

In the little race track manual, it shows how to switch between the two positions (including torque specs for the fasteners)

mdrums

I only got the owner manual with my car...got it used from Champion 2018 GT3...no extra manual about track adjustments. I guess I could by this from my local dealer? Champion has been horrible with after sales service and issues...there used car manager Thad is a total ***!

Petevb

Aero balance is the key, much more important than the absolute amount, and virtually every handling comment listed in this thread relates to getting the aero balance where the drivers prefer it.

Canards add only a small amount of downforce, primarily by increasing the vortex running along the rocker panel and thereby improving underbody sealing. Expect minimal downforce gains for a moderate increase in drag, but any increase in front downforce must be balanced in order to prevent instability- you will need to do something at the rear to balance it out. A Gurney flap should do the trick- on most modern wing profiles it’s primarily a quick and easy way to tune downforce/ balance rather than any secret sauce (meaning it will increase drag slightly).

Canards will produce nowhere near enough downforce to cause bottoming. For reference when the 997 GT3 RS 4.0 added canards front downforce was increased by 6.6 lbs at 124 mph- far less less resulting spring compression than a full vs empty tank even as speeds climb.

Mr. Turtles

Thumbs up to the APR wing. It easily bolts on and off of the GT3.2. For my driving style... it eliminates most oversteer issues, just need to fit the Cup front lip now.....

Jickel180

^^Nice. Can you run a cup lip without the front fender wheel arch extensions that the cups have? These canards look like direct copies of the PMNA for a fraction of what GMG wants for theirs which I believe are the same design. I'm thinking of going with these since the original design was engineered by Porsche, vs. the others.

https://racecarsdirect.com/Advert/De...-porsche-991-g

https://www.olafmotorsportparts.com/en/products/