Throttle steer a Miata? How does the diff affect this?

I have a 1990 Miata with Xidas and an open diff for my HPDE car. Someone let me take out their 1990 spec car and I absolutely fell in love with with it because it was so predictable and I could throttle steer with the car. You want a little more oversteer? Add a little throttle. I can't do that with mine. Every time I try to get mine to slide I have to do with it trail braking or tossing the car around. On occasion it'll catch me by surprise too. I want to make my car like that spec car and I'm trying to figure out what the special ingredient was or was it a culmination of a few things. The spec car was just a spec car from what the owner said. He bought it turn key and didnt have too many details.

Could it be the diff? If I swap in a torsen will it give me these characteristics or should I be looking at something else?

More details on my car:

Front camber is at -3.0, rear is at -2.5 and toe is at 0 all around. It has Xidas that are ~700/400 and a set of Flyin Miata sway bars - front set at soft and rear on medium. Running a 205/50/15 RT660 tire

What's your front camber at? If it is stock, that's going to make the car want to understeer. Adding more camber like the SM car most likely had will be the cheapest way to get most of the way there. 

The easy answer is yes the torsen diff will let you do that.

The bigger question is why you want power on oversteer......beyond you find it fun?

I teach people to throttle steer cars and the diff makes no difference to the technique. When you ease off the throttle a car tightens it's line. When you roll in more throttle the car takes a wider arc.

If your car is spinning the inside rear tire coming off corners then put the limited slip in it.

Back in the 90s I raced a Showroom Stock 1.6 Miata. You could make that car do anything a Spec Miata can...........the big difference is the Spec Miata will respond quicker.

I suspect the issue has more to do with alignment settings rather than the diff.

With all that said I'd put the limited slip in the car regardless as it should help the car exiting tight corners.

Also note that the 1990 Spec Miata probably didn't have a torsen.  IIRC, the rules (NASA ones, at least, not sure about SCCA) allow a 90-93 to run the stock VLSD or the Mazdaspeed clutch-type diff.

You want a little more oversteer? Add a little throttle.

Did you mean take away a little throttle?  Adding throttle usually creates understeer, at least until you get to the point of breaking the tires free.

I can see how the diff could have an effect. Tires only have so much total traction available, so if they're close to the limit on cornering and you ask them to deliver some forward acceleration as well, they're going to lose some cornering grip. An open diff will send the torque to the unloaded inner tire only, an LSD should send it to both - thus affecting the tire that is generating most of the cornering grip.

I have to admit I haven't really thought about this before. I agree with cyow5 that there may be a whole bunch of other setup questions in place. If you're running the usual Supermiata setup of lots of front camber and a big honkin' front sway bar, you're going to be biased a bit more towards understeer. SMs aren't allowed to run those massive front bars so it will have a different balance. Supermiata's numbers tend to assume more than stock power, which generally needs a bit more of an understeer bias to help put the power down.

Spec Miatas are a lot more finely honed than people think, a good one is spectacular.

In reply to cyow5 :

front camber is at -3.0