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Recently competed in SCCA Time Trials at Road Atlanta. I can happily report that the 718 GT4 is very competitive in class and did very well overall as well. I set a new PB, won my class, set a new class lap record of 1:32.8, and finished 3rd overall. Conditions weren’t perfect, or I think a high 1:31 to low 1:32 was possible. It was 75 degrees, 100% humidity with some fog, and overcast. Also of note, several of the big hitters weren’t there this year, so finishing 3rd and the class win got a lot easier. Thought some people might want to know what mods and how I have my car set up, because it seems to be working very well.
For alignment I’m running -2.75 camber in front and -2.2 camber in rear. I have 0 toe in the front and am toed in 2.2 mm per side in the rear. Swaybars are M/M. I have Elephant racings front droplinks, and Tarett rear droplinks. Had Tarett all the way around, but broke one of the fronts, so switched to Elephant. I’m using clubsport camber plates and shims in the front, with TPC caster pucks. In the rear I have TPC rear toe links.
The struts are stock, but I have Swift springs, 80 N/mm in the front and 100 N/mm in the rear. I also have a DSC controller with the OTS RS file. For this event, I found the street setting was much better then the sport setting. I Didn’t have as much grip in sport, and the car felt wasn't composed over bumps. Settled down and had noticeably more grip and stability in street. Other tracks, sport has felt better then street.
For Power I’m running BC Fabs manifolds and OPF delete, which is an under-axle pipe. It’s connected to a Cargraphic track/competition silencer. I also have an OTS M-engineering stage 2 tune.
For wheels I run Forgeline GS1R with 19X9 in the front with 7 mm spacers, and 19X11 in the rear with 5 mm spacers to clear the rear toe link. For tires, to stay class legal, I must run 200 TW or higher. I used Falken RT660s in 265/35 in front and 305/30 in the rear. My fastest lap was set with the pressure at 35 psi all the way around. The left rear was rolling over some, so I raised it to 40 psi for later sessions, but the sun came out and track got greasy, and I was slower by 0.3 seconds.
I used stock rotors and calipers with Castrol SRF fluid, and Ferodo DS 3.12 in the front and Ferodo DS2500 in the rear.
For Aero I used the Fabspeed risers, because they were the highest, and moved the wing to the rear of the car by about an inch. They also raise the wing high enough, that it gets it out of my vision. I went with Dundon front canards and rear bolt on wing, set to 10 degrees. I probably could have lowered the angle a little bit, but didn’t want to mess with too much, with limited opportunity to set a fast lap. I lost about 3 mph on the back straight with this set up, but picked up 2 seconds a lap, so I think it was a decent trade off. I also have the GT4RS underbody aero parts.
Overall, the car felt very balanced. I was able to rotate the car on entry. Mid corner was very neutral. Could get a little corner exit push, but that was due to my lack of patience on letting the car finish the turn. When I did, the car was great. Very easy to trust and lean on. Of the top three cars, the first place car was only good for a lap maybe two and needed extensive work between runs. The second place car was a team of Toyota engineers, which again needed 6-7 people working on it between every run. I drove my car 5:30 hours to the event and back home again. I relaxed and enjoyed watching other cars run, between my sessions. The only change I made was to air pressures. So overall all I'm very pleased with the car and car set up, and very impressed with how it performs. My fastest lap from the weekend, which I posted in the Best Lap times threads also:
It’s been a couple years since I’ve raced at Road Atlanta but hope to be there for the Super Tours race in March.
I’m happy to see the dundon airfoil on risers is working for you, I think I’ll be leaning that same route over the winter on mine as well!
Do they provide any data on the airfoil or happen to say what the critical AOA is? I wonder if there isn’t separation when set at 10* once you account for some of the downwash over the rear hatch.
It’s been a couple years since I’ve raced at Road Atlanta but hope to be there for the Super Tours race in March.
I’m happy to see the dundon airfoil on risers is working for you, I think I’ll be leaning that same route over the winter on mine as well!
Do they provide any data on the airfoil or happen to say what the critical AOA is? I wonder if there isn’t separation when set at 10* once you account for some of the downwash over the rear hatch.
No, really not much info. I'm sure Verus can provide that though. I just haven't reached out to them. I was told that most people have been running 6-8 degrees. I had just been at Barber and bumped the AoA up to 10, since it's a fairly low speed track. I left it at 10 for Road Atlanta, with the intentions of dropping it down some, but was turning good laps from the start, and the car felt balanced, so I just left it alone. I need to spend more time there and dial it in. Might be able to pick up some more time, by taking some angle out.
Side note, if you go with the Fabspeed risers, you'll will have to use different bolts, nuts, and washers to get it to mount to the wing.
Thanks for sharing your experience and setup. A few questions regarding your mods:
- given you are using the camber plates are caster pucks needed to further dial down the caster?
- curious about your experience of DSC on track
- for 4rs underbody aero bits do you feel they add more downforce front or rear or both?
- your choice of brake pads seem to indicate you are moving the brake bias forward. Are you doing this to further reduce the instability under braking? Do you still get those with toe link + 2mm toe in + DSC + stiffer springs?
Thanks for sharing your experience and setup. A few questions regarding your mods:
- given you are using the camber plates are caster pucks needed to further dial down the caster?
- curious about your experience of DSC on track
- for 4rs underbody aero bits do you feel they add more downforce front or rear or both?
- your choice of brake pads seem to indicate you are moving the brake bias forward. Are you doing this to further reduce the instability under braking? Do you still get those with toe link + 2mm toe in + DSC + stiffer springs?
Thanks, and I'll do my best to answer your questions:
-Yeah, the camber plates helped a lot with the caster. Prior to that I was rubbing the front wheel liner, and camber plates took care of that. My friend that sets my alignment, would always complain how difficult it was to set the caster, so I added the caster pucks just to make his life easier, but no they aren't necessary. I noticed no difference in the car handling with or without them.
-For DSC I've run a few different programs. I did the standard GT4, the GT4 with toe links, the 30% stiffer program, and now the RS file. I've even played around with some custom adjustments. I typically will run sport on and off when on track, to see which feels better. Sometimes it's sport on, and sometimes sport off, but it's usually a small difference, At Road Atlanta it was a significant difference, from struggling to get the car to rotate and put power down, to pretty rock solid. That's the first time I really felt it was a dramatic difference.
-It's really hard to say on the 4RS underbody aero, because I put it on the same time I added the Dundon aero parts. But for the price, it has to be the cheapest mod I've done, and took about 5 minutes to install. Biggest thing I noticed with all the aero parts is how much more confidence I had in the braking zones.
-So yes you are right, I'm trying to move the braking bias forward because of the tail wiggle. So I started off with factory toe links and ferodo DS3.12 all the way around. Never felt great in the brake zones. I added rear toe links, and there was a small improvement. Switched the rears to Ferodo DS1.11 and another small improvement. Switched to Ferodo DS2500 and another small improvement. I added stiffer springs and those also helped a little bit. Finally added the rear wing and that helped a lot. With this combination at Road Atlanta I've moved my initial brake point from the billboard to around the 300 marker. I'm not the last of the great late brakers, so I'm sure someone that is, could be much later on the brakes.
Even stock I could get the car not to wiggle, and even with all the mods I can get the car to wiggle, but there is a significant improvement with how hard my initial braking can be, and how confidence inspiring the brakes are now. This car's braking was really the one thing I really didn't like about it, and it is much, much better now. To officially answer your questions, yes if I wasn't smooth with my brake application I would still and can still get the tail to wiggle with the DSC, toe links, and springs. To be clear it would only happen on highspeed to low speed braking like 140-150 mph down to 35-55 mph.
11-11-2022, 04:46 PM
SCCA TT setup for Road Atlanta
