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flier129 and I might try to run a car next year at RA and Mid-Ohio because of this thread. Set exceptions way lower for us then you guys.
Time Attack Miata motivation intensifies!!!!
Road Atlanta = RA btw.
The "Street" record for GTA and Grid.Life for RWD is ~1:34-ish at RA. If we can get the car setup to work well in T1 and T12 with 300+ rwhp, 2300lbs, "S1" aero, on 245 Rival-S(or RS4s maybe?) on 10s then I think it's possible to put the miata up on the record list for Road Atlanta time-attack
I feel like Mid-Ohio will actually be easier to do well at. We'll lean on other sources to get that accomplished (Street RWD record is 1:38....)
Why limit yourself to a compromised solution that you are not required to make?
S1 aero works well for S1 SPMs which run spec aero, but it's by no means the best thing you can have on a time attack car. You're allowed more, do more - build to the extent of the rules, it's more than likely that the class winner and record holders will.
Why limit yourself to a compromised solution that you are not required to make?
S1 aero works well for S1 SPMs, but it's by no means the best thing you can have on a time attack car. You're allowed more, do more - build to the extent of the rules, it's more than likely that the class winner and record holders will.
Yeah, roughly "S1". I'm actually not sure if splitter+air-dam is allowed with Grid.Life in Street
Yeah, roughly "S1". I'm actually not sure if splitter+air-dam is allowed with Grid.Life in Street
Obviously aero will be a learning curve, lol.
Its an interesting challenge. Start a new thread just for this event prep and link it here. We can dive into the rules and come up with the best aero within your budget and Fabrication resources.
So I'm fairly 'ngant of aero and what components are actually needed on a TA miata. I've watched Kyle.Engineers videos on YouTube and that's about it!
I do know RA decently enough, though. T1(0:17 in video) and T12(1:44 in video) are key in regards to aero. Huge elevation changes in both and both are FAST.
The top-speed on the front straight after going thru T12 isn't that much lower than the top-speed on the back straight. I think pushing the front-bumper out, Bullet style, can be done and should net some on those turns. An air-dam is obviously key to keep the dirtiness off the front-end on the long straights, but unsure on what can be done on the rear wing. Putting power down out of T7(1:01 in video) is also really important.
I hope we can get Lars' car out to a couple of RA events next year before GL. Then, I'll stick an AiM Solo in it to collect some data. Though I believe the initial testing will be on the ACE's lol. So that data might be iffy. I'm not opposed to putting my car on jack-stands and pulling the Xida race off it to run on Lars' turbo car for the actual event, I even have spare 1000# front springs to use. But I don't want to do that all season long, obviously.
I'd characterize RA as an all-rounder track. Aero matters as much as power or mechanical grip. Gearing will be key. Less an issue with a turbo but make sure you don't have any big gearing dips or throttle response issues.
My read is no limits on front aero, just canards. I'd skip the canards, very draggy. Since it's not w2w, you're not worried about someone running over it. That leaves a big *** splitter. Crusher style air dam. Build the dam to completely shroud the front tires even when turning. Tires should be shrouded with steering wheel at 90°. I'd run something smaller than Bullet for RA ,but not much. The end plates on Bullet were Buttonwillow specific. I'd go maybe 30% that size.
Wing is easy, 2D foil like a GT250 or similar, with Gurney. Max width allowed. OEM NB is 64". With flares, wider. No restriction on end plates so make them huge. Plate area should be roughly 20% above foil and 80% below.
Diffuser allowed but with no flat bottom to feed it it's a waste of resources.
Front undertray to axle centerline, a no brainer. Do your best to get it as close to the tire as possible. We cut ours so it just barely cleared the tires at full droop and lock. The rules allow fwings, and front diffusers but they are hard to make effective with good exhaust flow. Meaning big fender vents and such. I'd skip front diffusers. Likely GL will consider and dive plane or 3D shape in the splitter as a canard and impose the 5" rule. So leave those features out. The gaping hole ion the rules is spliitter and end plate dimensions so go big there.
The B pilllar can be shrouded to reduce drag. Build a flap that extends inwards as far as your seat/cage allow. Remove OEM mirrors if you have them. Very draggy. Lift the trailing edge of the hard top 5-10mm off the rear deck. It relieves pressure build up in the cockpit and reduces drag. That mod is not legal in Supermiata so ours was tight. Make sure your body panels fit as tight as possible. If you have big gaps in the front of the car, cover them with clear bra material. We didn't have any so we used Gorilla tape. Hey, it worked..
While the aero setup in Bullet was effective, it was't the only reason the car went fast. We did a 1:44.9 on fresh 245 A7's but also did a 1:47.4 on 205 R7's. The lesson there is mechanical grip and balance. I want the mech grip to be neutral on turn in and mid corner, slightly tight exiting. This allows fine tuning line on the way in and through mid corner but allows early power application once the exit is lined up. As aero loads increase, I want the car to be tighter on entry, through mid corner and exit. Don't be afraid to work the fronts hard, it's not an enduro. This allows higher entry speeds and earlier application of WOT.
You'll need some big springs rates. Our fastest S2's, with virtually no aero, 225/45 RC-1's and 140whp run 900/500# with 1.125 & .562 bars. S1's are running 1100/500 with 1.25 and .562 bars. Bullet ran the same 1100/500 but needed like 1400/600 probably. We ran the same ride height we run everywhere else, 4.5" pinch weld F/R with driver. Only works with ELBJ's. The S1 splitter on Bullet is 3.5" off the deck. The SLB splitter was built at 4" to make sure we didn't tear it off as we didn't have a spare. Lower is better.. provided you don't tear it off.
With a turbo, it's safer to gear a tad too tall than run out of gear. Don't just look at your redline but the actual shape of the powerband. Our redline was 7400 at SLB but it made peak power at 6000. So we short shifted here and there with a 3.9 diff. If running stock redline, maybe a 3.6 for RA.
275's overkill for 300whp I think. 245's just right.
I'd characterize RA as an all-rounder track. Aero matters as much as power or mechanical grip. Gearing will be key. Less an issue with a turbo but make sure you don't have any big gearing dips or throttle response issues.
My read is no limits on front aero, just canards. I'd skip the canards, very draggy. Since it's not w2w, you're not worried about someone running over it. That leaves a big *** splitter. Crusher style air dam. Build the dam to completely shroud the front tires even when turning. Tires should be shrouded with steering wheel at 90°. I'd run something smaller than Bullet for RA ,but not much. The end plates on Bullet were Buttonwillow specific. I'd go maybe 30% that size.
Wing is easy, 2D foil like a GT250 or similar, with Gurney. Max width allowed. OEM NB is 64". With flares, wider. No restriction on end plates so make them huge. Plate area should be roughly 20% above foil and 80% below.
Diffuser allowed but with no flat bottom to feed it it's a waste of resources.
Front undertray to axle centerline, a no brainer. Do your best to get it as close to the tire as possible. We cut ours so it just barely cleared the tires at full droop and lock. The rules allow fwings, and front diffusers but they are hard to make effective with good exhaust flow. Meaning big fender vents and such. I'd skip front diffusers. Likely GL will consider and dive plane or 3D shape in the splitter as a canard and impose the 5" rule. So leave those features out. The gaping hole ion the rules is spliitter and end plate dimensions so go big there.
The B pilllar can be shrouded to reduce drag. Build a flap that extends inwards as far as your seat/cage allow. Remove OEM mirrors if you have them. Very draggy. Lift the trailing edge of the hard top 5-10mm off the rear deck. It relieves pressure build up in the cockpit and reduces drag. That mod is not legal in Supermiata so ours was tight. Make sure your body panels fit as tight as possible. If you have big gaps in the front of the car, cover them with clear bra material. We didn't have any so we used Gorilla tape. Hey, it worked..
While the aero setup in Bullet was effective, it was't the only reason the car went fast. We did a 1:44.9 on fresh 245 A7's but also did a 1:47.4 on 205 R7's. The lesson there is mechanical grip and balance. I want the mech grip to be neutral on turn in and mid corner, slightly tight exiting. This allows fine tuning line on the way in and through mid corner but allows early power application once the exit is lined up. As aero loads increase, I want the car to be tighter on entry, through mid corner and exit. Don't be afraid to work the fronts hard, it's not an enduro. This allows higher entry speeds and earlier application of WOT.
You'll need some big springs rates. Our fastest S2's, with virtually no aero, 225/45 RC-1's and 140whp run 900/500# with 1.125 & .562 bars. S1's are running 1100/500 with 1.25 and .562 bars. Bullet ran the same 1100/500 but needed like 1400/600 probably. We ran the same ride height we run everywhere else, 4.5" pinch weld F/R with driver. Only works with ELBJ's. The S1 splitter on Bullet is 3.5" off the deck. The SLB splitter was built at 4" to make sure we didn't tear it off as we didn't have a spare. Lower is better.. provided you don't tear it off.
With a turbo, it's safer to gear a tad too tall than run out of gear. Don't just look at your redline but the actual shape of the powerband. Our redline was 7400 at SLB but it made peak power at 6000. So we short shifted here and there with a 3.9 diff. If running stock redline, maybe a 3.6 for RA.
275's overkill for 300whp I think. 245's just right.
So much thing to try in that post, great info!
Thanks!
Rule 4 reads that the splitter can only be 5" forward and 5" out to each side. That's slightly bigger and much wider than S1, but still not close to Bullet.
A GT250 can easily balance a 5" splitter with a gurney and big endplates.
5" of extra airdam width still covers 245s on 10"s easily.
Good luck! If I make it back next year I'll be in HDPE. With a NA car it's too annoying trying to turn a good lap time getting parked in the corners by slowly driven muscle cars who motor you on the straights. If I don't drive, I might come down and just lend a hand if you need one. I know a few folks in the area, so I can usually source spares quickly.
I currently have the BFW lexan wing and it's not balancing out well with my current splitter that is extended ~4" from the replica GV lip. GTC250 seems to be the ticket
I have a COT wing on my car with a 4" splitter. Wing is mounted on FM stands and custom endplates.
Right now the wing isnt as effective as it should/can be. As I havent had a hardtop till recently. I also have an air dam in the works. The wing is very good for the price. I run almost no AOA and even without a hardtop, its very effective.
I currently have the BFW lexan wing and it's not balancing out well with my current splitter that is extended ~4" from the replica GV lip. GTC250 seems to be the ticket
4" stick out is a fairly sizable splitter already, you're asking too much of the spoiler, S1 balances a 4" splitter with a GT-250.
I'd definitely do a GT-250 over COT wing, as wide as you're allowed to.
Missed the splitter length restrictions. That simply means you max it out. 5" wider than nose and 5" forward. Wrap it around as far back as you can and still stay within the 5" rule. What you want is surface area. Build either a modular end plate for the splitter or something that is quick release. That's how you fine tune a splitter. The bigger the end plate, the more downforce and drag. No end plates gives you a very good downforce to drag ratio. With the power you have, no plates would not be enough. Don't be afraid to build some cartoon oversize end plates. What you don't want to do is discover the car keeps getting faster as you add end plate area and then you run out of area to bolt on.
The air mas hitting the nose stalls and builds pressure. Pushes in all direections, including down against the splitter. That's where your downforce comes from. Some goes over the nose, some goes to the side. As that air moves laterally across the nose, it speeds up. Pressure drops as air speeds up. The end plates serve to slow down the air from escaping around the sides, less pressure loss. If you terminate the end plate against the fender creating a dead end for the air, drag is very high. Better to leave a gap there so air can leave the splitter between the rear of the end plate and bumper. How big a gap is where you experiment. We took a WAG on ours and it turned out to be pretty close. That's why you want a modular end plate setups with a few iterations to try.
If you add cables, try to keep them in the areas where the air mass is moving slowest, like near the centerline of the car. If you need to put them on the corners, make them as short as possible. Cables are shockingly high drag.
11-18-2017, 09:51 AM
Miata Time Attack Takeover: Gridlife 2018 edition
1
(Street RWD record is 1:38....)
