Alright, details of my car are as follows:
89 GX
2.25" straight pipe to a magnaflow muffler from mani back
JIC SF1 coilovers
Koyo Rad
16x8 Sportmax 002 wheels - 205/50/16 Falken ZE-512's

And that is pretty much it so far. Now from what I've looked into, my car should fall into the E class if it were stock, as its not turbo, but I've been put in CSP, which throws me against all of those Miatas, which isnt fun! Should I be in ESP? Or is that not even a class?

 

That sounds like CSP. Unless you don't have a limited slip, then you would be eligible for STS2, which is full of CRX Si's.

Yeah, the prepped miatas are good. Good luck.

 

If you still have a catalytic converter and an open diff, you will be in STS2. You will be in CSP if you are running no cat and LSD.

 

CSP if you don't have all your emissions controls (Cat, ACV, etc.), or have the S4 clutch type limited slip.

The wheels are too large for STS2, they only allow up to 7.5" wide.

 

Alright, thanks for clearing that all up. I have a straight pipe, so no cat, and still have an open diff.

 

Well, you can put a cat in there and change to smaller wheels if you want to race in STS2. Do you still have the stock emission stuff?

 

Nope, you would be SM2 with the replacement radiator. Sorry for the bad news. You thought the Miatas were tough try 700hp Corvettes, the Porsche contingent, three rotor RX-7s, and many other fast oddities.

I doubt anyone locally would care but I thought I would point it out.

 

I figured a larger radiator would be ok, since it doesn't give any advantage for autocross and it adds weight, but I guess not. They are not specifically mentioned until the Prepared section, then they say any water radiator is OK...

This is in the Stock section:

Alternate components which are normally expendable and
considered replacement parts (e.g., engine and wheel bearings,
seals, gaskets, filters, belts, bolts, bulbs, batteries, brake rotors,
clutch discs, pressure plates, suspension bushings, drivetrain
mounts, etc.) may be used provided they are essentially identical to
the standard parts (e.g. have the same type, size, hardness, weight,
material etc.), are used in the same location, and provide no
performance benefit.

I had figured that would be ok. When my radiator needs replacing I wanted to get a better one. I think if it fits like stock and everything bolts right up to it normally nobody will complain. Unless you win every race...

In general, at the local level I don't think they'd mind the extra half inch of wheel, especially with the tires being all-season 205s. With those tires, you're just out for fun anyway.

A Street Tire class for CSP may be the most fun if they do that.

 

Pretty much with SCCA rules unless it says you can do something...you can't. It is a slippery slope. If they say you can change radiators then someone would go out and buy a $10000 titanium, carbon fiber, gold (someone would try it if it would help them win Nationals) radiator.
I know I would love to change to a larger radiator in ASP but that is just the way it is.

 

That is true, but they also specifically state that the changes can't provide any performance benefit. This prevents small titanium radiators. They do also say that it has to be the same size and material.

I replaced the plastic and aluminum radiator on my Miata with a copper one (+ 10 lbs w/ water) for an auto transmission car. This is the standard aftermarket replacement. This adds capacity and weight and is not stock for my MT car.
I would say this should be legal since that's all they have (I think) in the aftermarket. I'm not sure if this is actually legal or not.