I think the XRG would make a much closer Spec Miata (or even Spec E30) car. Front engine, rear wheel drive, relatively light, and modestly powered. Even though it's a convertible, the RAC doesn't seem like a very good match because it's a mid-engine layout.

Does anyone know if setups could be checked using an InSim app? I know that the CTRA used something for some of their races, but I'm not sure exactly what they were able to monitor.

The RAC does have a mid engine, but with the added weight and moving that weigth all the way forward it puts the car in the right weight distribution F/R. It also has wider/low profile Road Supers and a double wishbone suspension just like a Miata, E30, Solstice or other performance FR cars. My choice in using it had nothing to do with it being a roadster.

I hate strut suspension.....

I'd be interested in a spec xrg / spec rac league if there was enough interest (and if iRacing doesn't suck me in - yet to be determined...).

Quote from Cue-Ball :

Spec XRG, anyone

http://www.lfsforum.net/showth ... ight=miata+xrg#post718059

This is a miata inspired xrg set that logoflamb posted some time ago, it would make a great base set for a spec serries

Quote from Gimpster :

Since Cue-Ball wanted a Spec Miata I build this setup based on the RAC. It's a little light but its close. In the actual class only things like toe, tire pressuer and camber are allowed to be changed. The ARBs, shocks, springs and gear ratios are fixed.

its making way too much power, its way too light, and the car handles aweful

its pretty far from a spec miata, sorry

Ok you are right. I did mess up on the set some. I based in it the weight of an SM2 miata making the HP of the MX-5 Cup cars. I have been working on the set some more and I am getting alittle closer.

The best I can do using the RAC to get correct suspension geomity and close tire size is a ready to run weight of 2459lbs(50%fuel + passanger) & 140hp. I am modeling it on my 94 miata, so the spring rates, shocks, ride hight, camber, toe, gear ratios and final drive all match what I am driving on a daily basis. The diff is a tough one though as mine has the torsen, so I need to do a little more research and find out if its a one-way or two-way locking diff and find out what the values are for it.

At this point it is starting to handel like my car, it does push a bit in the corners if you enter too fast but also has a bit of power off or braking induced over steer, just like mine when removing the rear ARB. It is not quite as steerable with the throttle as mine but I think the diff and tire pressures are the cause of that. It does react correctly to curbs with just a slight pull in the direction of the curb.

And that XRG N-Miata is no where close to what mine feels like. Perhaps its modeled on a bone stock miata with worn out shocks...

Quote from Gimpster :

I have been working on the set some more and I am getting alittle closer.

I'll give you first one a whirl in an hour or so.

Look forward to trying any improvements you might have done also

A spec server would be really a cool idea the more I think about it...

glad to see you're still working on it

I'm really excited about the set. My dad owns a 2001 miata and it's a blast to drive. Its got the factory sport suspension package and z rated tires and the torsen diff. I think thats about all thats not stock, and yet it still handles like a gokart.

I did some reading on torsen diffs, and not sure if you'll be able to simulate it with the clutch pack or a viscous diff. I'd say best bet is either open or clutch pack with very low preload, power, and no coast.

" When a Torsen differential is employed, the slower-moving wheel always receives more torque than the faster-moving wheel. The Torsen T-2R RaceMaster is the only Torsen to have a preload clutch. So even if a wheel is airborne torque is applied to the other side. If one wheel were raised in the air, the regular Torsens would act like an open differential and no torque would be transferred to the other wheel."

Its an interesting diff. how it works. It sounds like it has no preload at all.

"When attempting to turn with a torque sensitive differential, the outer wheel will need to rotate more quickly relative to the differential, and the inner wheel will rotate more slowly than the differential. Friction in the differential will oppose motion, and that will work to slow the faster side and 'speed up' the slower/inner side. This leads to asymmetric torque distributions in drive wheels, matching the TBR. Cornering in this manner will reduce the torque applied to the outer tire, leading to possibly greater cornering power, unless the inner wheel is overpowered (which is easier to do than with an open differential). When the inner tire (which has less traction due to weight transfer from lateral acceleration) is overpowered, it angularly accelerates up to the outer wheel speed (small percent wheel spin) and the differential locks, and if the traction difference does not exceed the TBR, the outer wheel will then have a higher torque applied to it. If the traction difference exceeds the TBR, the outer tire gets the tractive torque of the inner wheel multiplied by the TBR, and the remaining applied torque to the differential contributes to wheel spin up."

Nice ride gimpster. NB wheels look nice on an NA. Wish I still kept mine....

Quote from Gimpster :

And that XRG N-Miata is no where close to what mine feels like. Perhaps its modeled on a bone stock miata with worn out shocks...

Hmm did some research on SCCA Spec Miata Class and built a set based on the 90-93 Miata spec using the xrg (it has the same F/R wieght ratio is a little heavier with the same HP but gives similar acceleration and top speed to rl miata)

It's just a rough one for the moment and alot is subjective... would like your opinion though gimpster, would be a fun set for a spec serries how it is I think

I tried out the xrg and I must say it was a real genius move to use the RAC

The xrg just doesn't feel sporty and light...it kinda feels like a truck.

Maybe if it had road supers it would be better, but I'm constantly wrestling the thing around the track...I just don't think you'll get the same feel as a miata.

I did some tweaks to the setup that gimpster posted. I took away a lot more power and loosened the diff way up trying to match the torsen. If you get the inside tire in the air it spins freely, but the car will still spin both if you get em in a slide. Judging by the 1/4 mile times I think the power/weight ratio I have going is pretty good.

The car feels right. Its darty and quick, but understeers if you don't slow down enough. Our miata you have to at least tap the brakes before turn in otherwise you'll understeer. You need to get some weight on the front tires. The car seems to mimic this.

I just did 10 minutes around FE_club and had a blast. I got down to 50.27 as my PB. The car is a real momentum machine. You've gotta keep the pace up otherwise the whole lap is ruined. I think you could have some real fun, tight racing with this setup. Its the best feeling RAC setup I've ever driven :P

Spanks here is the one i hae been tweaking with. The diff you will have to adjust to your liking because there is no way to make it work right given the options in lfs. I will give yours atry tomarrow as it too late here now and I get up very early.

My real car also understears if you cary too much speed in to a corner, but I can also very easily brake it loose with just a touch of brake, alittle flick or some power-over. It's a bit stiffer, lower, and twitchy then a stock one with a street alighment. Mine has some seroius camber, and rear toe in, front toe out.

I did the math and this thing uses the corrent spring rates for my FMsprings, I can't find the info on the shocks though. Gears and final are correct, but this thing does have way more torque.

This is close to how mine would feel if I took the rear ARB off which has been recomend to me for autocrossing and track days. Mine is a bit more tail happy with a stiff rear ARB. The original owner was a drifter I think.

genraly setups give me 2/5 sec's a lap depending on the track

with the right set i can get around 1/2 sec's away from the WR

but the best set dosent allways suit every driver i know personaly i like a weighty steering and a lose back end on turn in but not exit

Quote from spanks :

The xrg just doesn't feel sporty and light...

After trying yours and gimpsters latest rac spec miata sets I have to agree the xrg isn't a patch on them.

Have definately fullen in love with the feel of these cars

Have tweaked gimpsters set a little more... I definately think it's possible to come up with a nice handliing car for some fun ontrack races, looking forward to it