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Higher center of gravity. 245/45-16 raises the car higher than a 225/45-15. No way around that.

Jim - I remember driving your car and I'm fairly certain it didn't have traction control. This is SM, and F1 style traction control is legal (available through many of the aftermarket ECUs). Theoretically it doesn't make the car faster, but even F1 uses it.

Scott

Donnie,

As Patrice said, if you want lots of power and grip you might as well go to D or E Mod. Most of the A, B, D & E Mod cars run 13 inch slicks on WIDE wheels (C Mod runs 13 inch slicks on NARROW wheels). The min weights are probably going to go up for 2006 but will still be tough to get down to in D Mod. However, think about whether you would use the car at "clean" sites where you can start runs with relatively clean tires or if it would be used primarily at dirty sites like L'burg and Sanford. Stuff sticks to hot (and even cold) slicks. But then I routinely see sustained G's in the 1.5 range and peaks in the 1.8 range

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Dick Rasmussen

FS 50 2018 Mustang GT

That's pretty much it. There are a couple of other issues involving proper wheel offset/spacing for large wheels but that goes back to stuff I've already mentioned.



My car had the best traction control-- my right foot. But seriously, I am aware of the possibilities but that doesn't always translate into reality. Getting a traction control system dialed in is not easy (even the F1 guys don't have it perfect) and more times than not, it will slow you down. It's something that would require *extensive* testing to get right but obviously that's part of the SM(2) game.

The good thing about Donnie's new car is that it already has ABS which is fairly rare on early Miatas. It has all the pieces in the car ready to measure wheel speed and it could be utilized in a TC system.

I think the big thing that keeps the "uber" SM(2) car from being built is not the absolute cost. Some of the national SM(2) guys have a *lot* of money tied up in their cars but they started with a car where it seemed "reasonable" to dump a bunch of money into. Lets face it, would you rather dump $50k into an M3, 3rd gen RX7, etc. or into a Starlet/Miata? Lipstick on a pig, anyone?

Enough bench racing...

Jim

Hey, I have a very fragile ego. I don't need someone to hop in my car and drive it 3 seconds faster than me. As long as I don't let you anywhere near my car, I can bask in the false sense that I'm actually a decent driver.

I think the more important thing is not whp, but wtq. I don't feel like I have any trouble putting down the power with ~210 whp. But I *only* have a 184 wtq peak, whereas I think your torque peak was ~230 wtq. Add to that the big difference with supercharger and turbocharger power delivery, with the turbocharger you have a surge of torque come on in the 3000 rpm range, with my car I start with ~140 wtq off idle and it gradually climbs to the 180 range at 5200 rpm and then gradually drops back to 160 at redline. The linear delivery is much easier to control. I had much more trouble putting down the power in the Mustang than I do in the Miata, but it made ~290 wtq. I believe I could have a ~280 whp supercharged Miata kinda like this and handle the the power even with a 225/50/15 tire reasonably well. The above dyno chart is from the maker of my intercooler and illustrates the ultimate potential of my system, of course it requires a built motor to handle the higher boost. Notice even with this kind of whp, the peak wtq is still only equal to what Jim had in his turbo car, which is the basis for my assumption that it still would be contollable on an autocross course since the torque delivery is more linear and easier to modulate. Now considering this is at least 310 crank hp in a Miata, at minimum SM2 weight you would have less than 7 lbs per hp. Thats better than a C5 Z06 and would be a shiteload of fun.

That's an excellent point Les! Finding the hp/tq balance is definitely key (at least without taking other measures).

My old turbo car did have a flat tq curve (~210 ft/lbs, actually) from 3300rpms --> redline but if you let it drop below ~3000rpms, you were in for a big tq rush. I can only remember 2 places where that ever really came into play and they were both very tight pivot cones (Dixie crossover and Danville taxiway). In those cases, you just had to be a little bit careful getting back in the gas. Well, maybe more than a bit careful!

I would say for national style courses, this would never be a factor. That's not to say you still didn't have too much tq but it was much more manageable.

I still tend to think that a 911 (or perhaps even a 914) would make a better base for an SM2 car since they can put a lot more power down without spinning the tires. I remember lining up behind Patrice on several occasions and watching him take off. Wow! If I launched that hard, all I got was wheel spin or even worse, wheel hop. It always felt like I was losing a 1/2 second to him just on the launch. Considering you can make BIG power with an N/A Porsche engine and thus lowering the weight limit to 1900lbs, it seems hard to beat. But that's a whole 'nother topic...

Jim

Jim is right, usually traction is not a problem on the 911 except maybe in the rain and on gritty surfaces. Even if I'm still having an open diff. on my car. For power I will see Saturday at the Dyno day, but I'm not expecting to see #, really higher than what Les Davis car as. But the possibility of making nice # is there.

Patrice

Yeah, I imagine having the engine over the rear drive wheels helps more than my Torsen LSD for traction and putting down power. I remember there was a guy running a turbo 911 in import drag racing at one time. He held the street tire record for quite some time and was famous for doing wheelies with 1000 hp and Toyo street tires.

I also should amend my comments above. I said I had "no" trouble putting the power down, but that is not really true. The first time out with boost in Sanford, the cars rear was stepping out alot. My S/C setup is not exactly like just having a bigger engine. Throttle tip-in has some issues. There is a boost bypass valve in the S/C that diverts the boost in low load situations and this valve has a split second response time from fully open to fully closed. Combine that with the fact that the S/C also has to refill/pressurize the intercooler. This requires an easing into the throttle after coasting or braking otherwise in a 0.2 second you go from 20 hg-in vaccum to 6+ psi. But, since getting used to that, I no longer feel that I have trouble putting the power down, and am ready for more.

Anyway Donnie, not that I'm looking forward to you coming along with a properly built SM2 Miata and whipping my butt, but it is undeniably alot of fun and I encourage your endeavor.

My car is not complete yet, but basically the culmination of several years of planning. I can absolutley say that I don't regret it at all. The car is by far the most fun I've ever had. Now, I just have to pay off that darn credit card and let it cool off a little before overheating it again with more go-fast goodies.

Donnie, take a close look at Dan Pedroza's SM2 Miata at Toledo That's about as well prepared as it gets. If you up the HP enough you'll really need to go to an RX7 rear end. (Ask Andy Hollis what happens to the early MX5 rears). All said and done the Miata can be made competitive in SM2 for Pro Solo, but have a hard time against the Vettes on the bigger tour/championship courses.
It would be cheaper and easier to build it into a competitive DP car, and somebody needs to run against Paula!

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SPIN or WIN!
there's no glory for going slow.

Alright, while it was fun to dream about, I'm not doing the SM2 car. I'm just going to part it out for my Spec Miata.

I'm not nearly a good enough driver yet, and adding something as complex as sorting a beast like *that* out to my already taxed brain is probably a recipe for disaster.

That said, I am planning to drive some faster stuff next year...I'd say chances are good I'll be running in whatever class the Cayman lands in since I have one of those on order. I'm fairly certain it'll be a SS car, so it probably won't be nationally competitive. But I'll probably bring it to some Tarheel events anyway.


--Donnie

The Cayman looks to be a really sweet car. I am not a huge fan of the open top thing (Miata, Boxster, etc) so the Cayman on paper looks to be a great car. I also think it looks a lot better than the Boxster and 911.

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Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Gonna AX one of these???? http://www.monacocoach.com/cayman/
You're right, don't expect it will be competitive in SS!

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SPIN or WIN!
there's no glory for going slow.

In the hands of the right driver, anything can be competitive locally.


--Donnie

I just wish Porsche had kept the Cayman to its early design goals. A lighter, stiffer Boxter that could be had with less euipment, and therefore cheaper.

But no had to go upscale and slot it between the Boxster and the 911. And doing so once again makes a car that is more capable, and faster, than the top of the line car. Much like the 944T's back in the day.

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