Enthuza Car

Mazda MX-5 Miata FAQ

Performance and Competition

Last updated: 30 June, 2010

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I'm interested in autocrossing my Miata, where can I get help?

Try the autocross mailing list. To join, send mail to autox-request@team.net. This is a large and busy list, and it is available in direct mail or daily digest form. Remember to include your name, home state/providence/country, and tell them you drive a Miata.

Also take a look ad Doug Quara's Autocross Tips with a list of allowable modifications compiled by Kate Hughes.

The Miata is classified in the B-Stock class of the Sports Car Club of America Solo II (Autocross) rules.  Miatas dominated the field at the 1994 Solo II championships in Salina, Kansas with Bob Klinger of Colorado Springs claiming the national championship. Eight of the top ten cars were Miatas. Note that most popular performance modifications to the Miata are not legal in the SCCA "stock" category.

Also, most dealers of performance parts and accessories are familiar with autocross and will be more than happy to give you advice (and sell you parts) to make you Miata quicker on the autocross track.

How can I improve the performance of my Miata?

Also see Jyri Virkki's page on Miata Turbocharging and Supercharging.

K&N makes a reusable air filter for the Miata that some vendors claim can improve your engine performance by as much as 2hp. In any case, investing in the reusable filter is probably cheaper for you in the long run than buying paper filters. This filter is the same for all Miatas (1.6 and 1.8L engines through 1995).

In the 1990-1993 1.6L DOHC engine, Bumping the timing from the stock 10 degree setting to 14 degrees has been found to increase HP and torque a tiny bit. Some people who have made this adjustment find that they must use higher octane fuel to prevent the car from pinging. Some people don't notice any difference. Some people complain that this modification makes their car run rough, kill, or just generally unacceptable. It's cheap to try, and if you know what you are doing, it's hard to hurt anything. Settings as high as 18 degrees have been tried with a substantial horsepower gain, although premium fuel was required to eliminate pinging. (This didn't work with oxygenated fuel.) See Miata Magazine Fall 1995 issue for details.) Note that you must connect two terminals in the diagnostic connector to properly check/set the Miata timing. The crank angle sensor is located between the cam cover and the firewall on the passenger side of the car. Check your factory service manual for detailed information on checking and setting spark timing. This is not legal to do in Stock class autocrossing.

There are noticeable horsepower gains that can be made by replacing the stock intake and exhaust components with higher flow parts. These items are available from many Miata vendors.

There are also many higher performance (and cost) options that exist for the Miata including nitrous oxide kits, superchargers, turbo chargers, and even complete engine/driveline replacements.

Can I put a V6/V8/Rotary engine in my Miata?

With enough modifications, generally anything can be done. Check out the Engine Conversions section of our Forum.

What size/brand tires should I use for Autocrossing?

Probably the most popular tires for Autocrossing the Miata are the BF Goodrich Comp T/A R1 (Autocross) and the Yokohama A008RSII (Autocross) Tires. Both are available in 205/55/14 and 185/60/14. Expert autocrossers feel that the 205/55/14 offers a slight advantage over the 185/60/14, but the larger size tire is more expensive. If cost is of no concern, and/or you need every hundredth of a second go with the 205/55/14. Otherwise, get the 185/60/14 and spend the money you save on practice. Many people have mentioned that the 205/55/14 will last a lot longer than a similar 185/60/14.

Are the 'R' wheels the lightest? / What is the weight of the wheels on the...?

See the table of wheel weights.

What other cars have wheels with Miata-compatible bolt patterns?

See the table

What kind of alignment settings should I use?

Miq Millman has compiled an alignment section that explores this subject.

Also see Lanny's Alignment Page

Several net.people have recombined the following alignment for autocross without compromising tire wear on the street.

~.7 degrees negative camber front, 0 toe
~1.0-1.2 degrees negative camber rear, 0 toe.

We have noticed no unusual tire wear with this alignment, and the car does feel a lot better than it did with the stock alignment. The car does wander a bit on the interstate, and it wants to follow grooves in grooved pavement more, but nothing We'd consider dangerous or excessive. This should simply be considered a starting point, the right alignment for you has to take into account the style of driving you do, the type and size of wheels, tires, and other suspension parts, and your personal preferences as to how the car should feel. Please be careful when altering your alignment, extreme settings can make your car difficult, or even dangerous to drive on the street.

At what RPM should I shift? Will I damage the engine?

You can't damage the engine by accelerating to too high an RPM. The Miata engine is designed with a rev limiter that shuts off the fuel delivery when the engine reaches approximately 7200 RPM. Go ahead and try it some time - you won't do any damage and its a good idea to know what happens so you won't be surprised if it happens by accident.

The Miata engine is also designed to give the highest horsepower in the 5000 to 6000 RPM range. If you're looking for free horses, just make all of your shifts above 5000 RPM. You'll have more fun doing it.

Also see the Miata Forum FAQ

My suspension 'clunks' when I autocross.

It is very common for the control arms to rattle back and forth in their mounts if the eccentric bolts are not *very* tight. They need to be torqued to about 150-180 ft/lbs to keep this symptom from happening, especially if  your control arm bushings are worn out.

Most alignment shops only hand tighten them to about 70-80 ft/lbs. Whenever we get an alignment, we always drive the car home very carefully and then put the car up on ramps and tighten the bolts further with a breaker bar we made (be careful not to move them and mess up your new alignment). If we don't do this then the clank appears on the first hard corner and the nice alignment we just got will be off. (Thanks to Randy Stocker for this tip.)

Editor's Note: Factory spec for alignment bolts is 69-83ft/lb in the front, and 54-70ft/lb in the rear. Use this suggestion at your own risk.

What aftermarket seats fit the Miata without modification?

The Miata has a very narrow seat tunnel and should area. The key to fitting aftermarket seats is the width of the seat and the shoulders. The tunnel can support a 19.5" width and the shoulder area can support about just under 20". (YMMV, always measure.). Seats reported to fit are: Sparco Rev, Sparco Racing, Momo T-Frame, Corbeau ForzaI , Cobra Sebring, MazdaSpeed, OMP (?),

The problem with most aftermarket seats is they they are intended for racing and will not have the ability to recline. The deap seat well also makes it difficult to get in and out. Mazdaspeed sells a reclining seat but they are about $1300/pair.We  have heard of someone using the 1st gen Integra seats with success. We personally like the Miata seat for daily driving - especially with the addtion of an aftermarket lumbar support or a towel stuffed behind the cushion.

Anybody got any that use existing holes?

Many manufacturers have generic brackets you can adapt.

Is it practical to put the seat in for events and then out again for daily use?

Yes, it is only 4 bolts to take the seat out.

Are they at all adjustable?

If they are adjustable then they are not race seats. True race seats are not allowed to have a recline function. The addition of the OEM sliders does give you some fore/aft movement but it is more limited then the factory adjustment since the seat are typically rigid at the thigh area.

What is the best tire pressure?

The owner's manual calls for 26psi of tire pressure. This is your starting point and is generally considered a good balance between ride comfort, handling, and road noise. However, it is not necessarily the "best" pressure, depending on what you are trying to do. A bit more pressure may be desired for higher performance situations where less sidewall flex might be needed. Too much or too little pressure will give uneven treadwear.

Do not use the pressure indicated on your tire's sidewall. This is typically the maximum rated pressure for the tire - it has no relationship to the "best" pressure.

Only you can determine the best tire pressure for you. Use the 26psi starting point, and use a gauge that gives you a consistent reading. (It doesn't necessarily have to be an accurate gauge, but it must be consistent. To aid consistency, always measure the pressure when the tires are cold.) Raise the pressure 1 or 2 psi at a time and re-evaluate the performance. If you like the change, keep it. If not, go back to the previous. If you can't tell the difference, then it doesn't matter. Don't let someone else tell you that you're wrong. There really is no wrong pressure. You just need to be able to feel the performance differences.

To get an idea of what other people like,  see this Miata Forum thread



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