Super Touring Light Miata (SCCA STL Class)
 

I’m toying with the idea of building an SCCA STL class car for season after next.

Here are the highlights of the class:
Weight with driver 2399 Updating and backdating between years is legal
Brakes - must use stock brakes
ABS – only from the car it was designed for.
Engine (N/A only)
11:1 Maximum Compression
No head porting
.425 maximum lift cams

Suspension – stock pickup points, shocks, swaybars, etc… are open
Wheels – 15 x 7 maximum
Tires are open
Differential is open as is rear end gearing

Thoughts:
Start with a 2002 chassis, Make sure it has sport brakes, 6 speed and ABS. I’m a fairly big fan of ABS – Is the 2002+ ABS that much better than the 1999-2001? I know a lot aren't. If I started with a 1999 chassis, it would be much cheaper to build it.
How easy would be to put a 1999 motor in a 2002 chassis?
Add an OS Giken differential, and play with gearing a bit, I’m thinking of starting with 4:3 and going from there.
Xida coilovers, ISC spherical bearings, etc...
Small 2” splitter by the rules and very small rear wing by the rules.
Engine I think should be a 1999-2001 with big cams, bored to 1849CC, flattop intake, COP, dry sump. Rebello believes they could get this to 225-235 hp – keep it under 8500 RPM to be reliable. They have several cam profiles for .425 lift
I’ve thought about the 2002+ motors, but not sure of all the differences, and also not sure the extra midrange torque would be helpful as the car would most likely spend almost no time under 5000 RPM.

Really looking for thoughts between the 1999 and 2002 chassis and engine combinations?

I've not kept up with SCCA rules in a few years, but wouldn't the update/backdate rule allow you to start with a 99 chassis then swap to sport brakes/02+ ABS/VVT motor/etc.?

I plan to run STL next year. In fact, just ordered some suspension today. :)
Looks like it will be more fun than ITS. Last I looked at rules, brakes were open. I've seen them with wilwoods.

I've also been told that the hot setup will be a 99 head with big cams. Apparently they can get better power up top on the 99 head due to better cam selection. There are interference concerns with the VVT head. The VVT head has been shown to make more torque down low, but you shouldn't be under 4-5k rpm at any point anyway.

IMO, 225-235 is very optimistic. That would have to be crank hp, and even then on a very friendly dyno.

Thats what it sounds like to me.

225 whp seems pretty optimistic for N/A 1.8. Even at 8.5k rpm.

I agree with Track, it would be extremely impressive to top the 200 number N/A. Emilios motor in crusher was severely built, and I think he was around 150 hp, though that was limited by his class. Also, miata2fast has a heavily built motor running itb's, and I don't think he's close to 200 either. I'm not 100% sure on any of the numbers I said, so don't hold me to it. Hopefully those two chime in on your build.

Good luck, car will be sick no matter what.

225whp n/a on stock ports isn't optimistic - it's impossible.

225-235bhp is ~190whp, which is probably doable with enough cam and revs.

yea, sorry whp is habit, thats why I said its a bit optimistic (in otherwords, I didn't mean to put the 'w' in).

Either way, I have still yet to see a dyno for more than ~180whp. Either way, go for it! I am not trying to discourage, just warn that the hp figure seemed a bit optimistic. Then again, those dynos probably didn't have the funding this would have.

It was 225-235 at the motor - Sorry for any confusion. I'm thinking 180-190 at the wheels. My motor now with 10:1 and a ported head is at 208hp on an engine dyno with a set of Integral stage 3 cams, no drysump. I think the drysump would add 5-6 hp, bigger cams should add a bit, 1 point more compression, but no ported head. Might be slightly optimistic, but maybe not. I know the FP/EP motors are pretty close to that.

The brakes are not allowed in STL. I have a set of the rules here. They are allowed in STU though.

G. Brakes
1. OEM brake systems must be used. Alternate OEM brakes rotors or
calipers from the same manufacturer will be considered.

I can't image trying to swap the ABS to an earlier car. Actually I can image it, but it would not be fun. I've put a Honda S2000 ABS system into a Mazda RX7, so I know I could, but I would rather buy the 2002 and swap the engine I think?

190whp and 2400lbs and they don't allow big brakes? Looks like they want a repeat of the T1 vette fiasco.

I think I noticed a difference betwen the 03 I had and my 99, but it might just be the EBD in the 03, I seem to be unable to dial in enough rear bias on the 99 (even with rear sport rotors).

There is a lot of FUD around VVT, especially in High comp, big Cam theoretical setups. It's not rocket science, it's just not that many to copy :)

Is the inteference (cam lobe to lifter pocket)less of a problem in the 99 head?
Or is the "interference issue" around the valve-piston clearance at max advance (which might be visited by mistake with poor VVT control).

Same manufacturer... wonder if you could get away with running some RX7 calipers or something? I've seen two Miatas now with them, both track cars. They built that set up long ago though, before there were willwood kits around.

We have built a STL Miata ran 2 events last year working out some bugs. Had a minor problem with a rod bearing and have the engine back out now. Going back together soon with different cams and should be even better.
We are going at this a little different than most are, we are running a 1.6 at 2132lbs

Your build sheet looks good except:
Flat top manifold isnt legal - Must be USDM part
Dry Sump Isnt legal

Just a couple things to look at before you spend money on stuff you cant have. Good luck with it and hope to see you at the track!

Here is a pic of our car, minus the aero parts in this pic...
https://www.miataturbo.net/attachmen...ine=1325515987

I get lot of customers ordering parts and getting set up advice for STL and STU cars these days. It seem there is a bit of money to be had if you do well.

Can someone with knowledge of the SCCA ST scene break down what contingencies/prize money is available and from whom?

I'm not crazy about the engine rules and 8" wheel max myself but it is a interesting engineering challenge going up against cars with a bunch more power.

From what I've read on the miata net the 01 come with bigger brake optional package which pre 00 do not have. Also o1 motors have the vvt...don't know if you'll keep that but that's an option. I don't know if there's any other performance changes between the nba/nbb models.

STL is a regional only class, so there are almost zero contingencies/prize money to speak of (as far as I know).

STU is a national class, it should have contingencies similar to other national classes. That is, Mazdaspeed contingincies of up to $500 for a win (if 4 starters). Also, Mazdaspeed pays $1000 for a division championship, up to $1200 for a June Sprints win. Hoosier, BFG, and Goodyear all have tire contingincies. Hoosiers is 2 free tires for a win (min. 3 starters in class), BFG gives 3 free tires for a win (min. 3 starters in class). Goodyear is 2 free tires for a win (min. 3 starters in class). Hawk and Cobalt also have a brake pad contingency of 1 axle set of pads for a win. Carbotech usually has a contingency program but it hasn't been listed.

So all in all for a National win with four starters (might be possible in STL/STU) you would get $500 cash, 2-3 free tires and a set of front or rear pads.

As I was writing this, I checked the SCCA website and it looks like for this year and onward STL is a national class. So all of the contingencies I listed for STU will apply. However, STL will run with STU at the runoffs, so no STL car would have a chance at the Runoffs... An STL car (or STU for that matter) running at a "Regional" race will not qualify for any of these contingencies, only at "National" races.

BTW entry fees for National races are on the order of $350 for a single and $500 for a double. So the entry fee will suck up most of the cash winnings from Mazdaspeed.

The lifter pocket is the same between the 99 head and the vvt head IIRC. It is not that big a deal to modify the lifter hole for the camshaft to clear however.

I would think that interference of valve and piston on a vvt motor would be an easy problem to solve. What might not be so easy is to keep the vvt working properly and from breaking other parts at such a high rpm.

If you have your heart set on running in the SCCA why not run in a prod class? There is no contingency money available in regional racing or tire contingency for that matter. At the national level, running up front can help offset cost of entry fees and tires.

As far as hp, 180 whp seems to be good for a 1.8 ep car, 150 is big for a limited prep f car. My car dynoed at 154 and 112#, with intergal 4 cams, 10:1 Pistons and the allowed porting and crank work. Tuned on 100 octane race gas.

Now I see the above post showing STU will be a national class.:facepalm: Plan on spending some bucks for an engine with nationally competitive power.

Our first STL Engine made 150whp and 120wtq and was limited to 7500rpm, it was a 1.6L

New engine is almost ready to go in...

On a 1.6 I would think 150-165 is possible, but difficult without the 99 head.

STU is going to be tough. A friend of mine is building an S2000 with about 300 Crank HP and revs to 10K RPM. To be competitive you would need boost, and even then I'm not sure.

STL is a national class as well, and with the limits the Miata should do fairly well. Weight is a concern of course at 2400lbs for a 1.8. EDENS approach to use a 1.6 at 2132 might be faster, hard to know. Easier for sure.

What are the rules for head porting in the class? Im guessing the wtq number is d/t compression ratio.