icantlearn

Hey everyone.
My first GLTC race is coming up soon (March 6-7) at COTA and I would like to hear your thoughts about my plans to get my car class compliant.

My car is currently a NASA ST4/Supermiata S1 car so getting to the power/weight is really kinda difficult since I have a 8% modifier for the turbo (2%) and aero (6%). I think its best to run the car heavy for this event in exchange for more power. It's a fast track with long straightaways so power > weight.

Here are the numbers all at 8% mod penalty and comp weight:
185whp = 2497lbs
190whp = 2565lbs
195whp = 2633lbs
200whp = 2700lbs

Quick car rundown:
Stock VVT head
8.6:1 supertechs
Flat top mani (I might have to swap this for a VICS mani to choke it out a bit)
TSE 6258 kit (low boost actuator)
3" exhaust
Pump 91/93

Right now, the car weights 2388 with me in it no driver gear/ half tank of gas, and it makes about 260whp on 11psi.

I think the best option is 190whp at 2565 (8%). It would be roughly 170lbs of ballast. So im not sure if its a good idea to add more or not. im worried that since ill be on a 225 r7, the tires will get greasy too fast if the car is heavy, but then again, COTA has lots of long straights to cool off the tires. So I dunno.

An idea I had to was to have multiple tunes for each power selection, so I can flash the car and ditch some weight if I need to. I think this would be a good idea anyways due to dyno/weather variances.

Im curious to see what you guys think is the best plan of action.

flier129

iTrader: (7)

Ditch the front splitter, it's not worth the extra 3%. Make an "under-tray" flush with the air-dam both vertically and horizontally.

So with the 5% modifier I'd do ~195rwhp ~2560lbs at COTA. Beat the other guy to the next braking zone

I highly doubt 225 R7s will get greasy in the 20min sprint race, especially considering the looonnnggg straights at COTA.

Aim for 2:28s! Good luck, wish I was making it with ya.

Midtenn

iTrader: (15)

For COTA strip all the aero that creates drag, lower tw tires, max power, and make your car wide on the corners. Worked for the guy who won 3-4 races last year. COTA is a different beast of a track compared to most others on the GLTC calender with two long straights. With long straights, it makes (legally) defending against a higher HP cars tough.

flier129

iTrader: (7)

Here's a decent example of that. Todd managed pole in qualifying with his S2K with aero and R7s, but couldn't quite hold onto Hoe-town's power/low-drag/street tire build.

Qualy:


Race 2:

Arca_ex

iTrader: (2)

Yeah I was there last year and got to watch everything. The car that was winning had no modifiers for aero, just front airdam, undertray, rear ducktail spoiler which is all free. Then it's FWD which gets a power to weight boost, and he also went to street tires for another power to weight boost, and ran heavy, again for more power. Add all that up and the car was so much faster down the straights that it wasn't even a competition. That is until his tires started to fall off at the midway point with the Yoko A050's. The lighter RWD aero cars on Hoosiers would be chipping time away but not anywhere near enough to catch him by the end of the race. The power to weight and drag difference was so massive that the one time he started near the back of the grid because of mechanical issues, he freight trained the entire pack on the green flag and beat everyone to the first corner.

This is the one track that kind of "breaks" the GLTC classing system if you put together a build that would struggle to do well at any other track.

Efini~FC3S

iTrader: (4)

Is it worth noting that none of the really fast GLTC guys were there that weekend?

Like if Kutil or Aaron were there running their standard cars, would Houghton have done so well...?

Midtenn

iTrader: (15)

Houghton did have one "cheaty" aero mod, but its now illegal. His radiator opening in the air dam was also the top of his front undertray, effectively turning it into a splitter. The car was run through CFD, so it wasn't an accident. The rules have shut that door now.

If it were me, I'd run an air dam, either 100tw or 200tw tires, and a small 6" spoiler.

doward

+1 to all the above, especially the now-illegal aero design of Houghton's tsx.

All the fastest Miatae in GLTC are making airdam-only front, wing rear aero work due to the splitter penalty. Generally, their airdams are lower and shroud the tires better than the super easy early Supermiata S2 examples. This gets into class-specific optimization though, and may be over thinking the current situation.
(My splitter is essentially 'free' in GLTC trim because n/a BP4W at 173whp, and I want to stay at/over 2251 for 225 R7s. I put it top ten twice in a full field of ~65 at mid ohio last summer.)

IIRC, you have no setup data or much driving at all on a matched set of new tires?
I would run the car as close to as-it-sits as possible, but on fresh tires of whatever fits the ruleset. 245/4015 Rival S might give you a big enough mod factor break to avoid huge ballast or keep some power in it.

icantlearn

Dan, thanks for your input. Yes I have no data on good tires. But I just mounted a sticker set of 245 AR1. Ill be at Sonoma this weekend so we will see how that does. No events planned after except for COTA. But I would be surprised to see a 245 perform better than a 225 or 205. So If getting off Hoosiers is the move, I think a 205 ao52 on a 9 is my best bet. Apparently they are nuts.

Im worried that my car will be over sprung if I ditch the splitter and step down to a less grippy tire as I have 1100# springs in the front. So this is something for me to consider. I can always swap them for the 900# springs I had on before if this poses an issue. To add, my wing is huge, so even at 0AOA its still gonna make the car push. I can swap to a S2 style spoiler, but those are draggy if not laid flat.

I asked Adam if I am allowed to change car setup during the event, and he said yes so long as I have tech sheets for each setup. So I don't have to commit to one setup for the weekend. I will use my practice sessions to gather as much data as possible before qualifying.

Arca_ex

iTrader: (2)

Yeah I always thought about "what if the known fast guys were there" but when I think about it, they would have gotten beat as well. Houghton would have just freight trained them in every straight because they all run wings and Hoosiers. If you've ever had to deal with an out of class car that wants to race you but has more power, you know how hard it can be to pass them even if you're like 2 to 3 seconds a lap faster. And the bigger the straights, the harder it becomes.

As for tires, I wouldn't move from 225 R7 to 205 A050. The power you get back is not going to make up for the decreased grip and also them falling on their face before the halfway point. When people move to street tires they usually go up in width as the rules allow them to as well as get the additional power, this makes up a little bit for grip but more importantly heat management and more consistent race pace. Miata's are just screwed though because of having to run 15" wheels. Wasn't houghton running on like 295mm tires and was around 2800lbs all ballasted up or something crazy like that?

doward

yea, thats why I'd go 245 Rival, or CR1 if you wanna airfreight some in on time. It will put power down and tolerate heat better than a 205 yok, even though it might not be appreciably faster in single lap pace. Take the mod factor break to pay for the splitter and add power.

I really dont like Miatae at/over 2500lbs. My oem style hubs last about 3 hours each up there.

icantlearn

Ok so game plan is to leave my splitter alone, run a 200tw 245 (I just bought sticker AR1, RIP), and run as close to 2500lbs as possible?

I dont think its a horrible idea to bring along another "splitter" that doesnt protrude and see how the car does with that. I can swap it out during practice, load a new tune, and see what happens.

flier129

iTrader: (7)

Don't run the protruding splitter, it'll be faster especially at COTA. The %balance front/rear is "ok" at ~10%.... I'd guess your current setup around ~65% front, so removing the protruding splitter would drop that % more towards the rear. Reduces some drag, but more importantly 3% more power.

icantlearn

Well, the car is actually pushy in the current setup (on old tires mind you, will report back after tomorrows track day on freshies). I cant really drive it with the throttle the way I want to. Thats why i'm scared to get rid of the splitter.

BUT. I can always bring 2 aero setups to the track and see what I like better, assuming I get 2 practice sessions that is.

apexanimal

One thing to keep in mind at COTA last year, was that Houghton tuned into his t/a skills and did lap 1, turn 1 better than anyone else on a consistent basis.
His setup there is hard to argue with, but he didn't have the fastest time of the weekend - he maximized his setup and took advantage of his skills and his car's strengths better than anyone else that weekend.

I have been using the 245 AR1 myself, but will be moving back to another 200tw 245 tire after these ar1's die - they hold up well during a race. rival's? not so much, but hopefully with the straights the outsides will stay cool enough.

I also totally agree with trying to run an undertray only (if you're able). If you've got push at high speeds, dial your rear aero down. It doesn't take much aero to balance out an airdam-only front setup.

icantlearn

I cant dial out the wing any more, its already at 0 aoa. The only thing I can do is remove the endplates or move over to an s2 style spoiler.

Ran sonoma yesterday, the 245 AR1 had a ton of grip. Tire temps revealed I have way too much camber. The car felt pretty balanced sans high speed push. So im not really thinking an undertray + current wing is a good idea. It will understeer everywhere.

flier129

iTrader: (7)

What if I told you.... you can run negative AOA?!

I think you're overestimating how much that change of % of aero balance will affect your handling. Maybe try it and see?? If you're pushing like crazy start with changes to the.... I dunno..... suspension?!

icantlearn

Its not pushing like crazy on these tires. Mild high speed push.

Ill put an undertray on the car and if it sucks ill put the old one back on and flash the tune for it.

I wonder if the Rival S 1.5 is a better option than the AR1 in race conditions.... hm. Decisions decisions.

doward

2% more power at the same weight, but a street tire is basically never a better race tire unless you can optimize the car/setup to the rules for it. We don't have a 265mm 200tw option in 23", so...

I must have missed that GL copied NASA again and allows the RR as a 100tw. Why don't more people run 245/40/15 RR?

icantlearn

because they are expensive and not much faster than the AR1.

I guess what I mean to say is I wonder if its a good idea to leave the car on AR1 for 2% less power.