After two years of not having a true sports car the void was starting to eat at me. Trying to make family cars into sports cars is expensive and only so effective, so after the Accord I had pretty much decided that for the best driving experiences one needed to delegate tasks. The A4 is a brilliant luxury sports sedan lacking only the right parts before it becomes a real GT car, so that role has been filled. But then I needed a real sports car, one with driving pleasure and precision as its primary intention. This is that car, a 1992 Mazda Miata. Super light weight. Double wishbone suspension front and rear. Fantastic steering. The best transmission of all time. A zippy, flexible, tunable engine. Easily upgradeable brakes. These attributes blend together as a seamless package that make for purely blissful driving anywhere but the freeway (where the Audi shines).
Forging Reliability
As with any used car repairs are in the forefront but with any luck modifications will squeeze their way in as well. The aftermarket for this car has anything and everything you could possibly want for it. In order for modifications to actually improve the driving pleasure of a car, the basic systems need to be in good shape (obviously). Hopefully the previous owner of the car will have kept extensive records of what repairs have been done. The big three I always look for buying a used car are the timing belt/water pump, clutch, and tires/alignment. On the miata the convertible top also falls in the category although I wouldn't let it stop me if a good car had a bad top. Those together are the most expensive maintenance that will likely be needed. Even if the new tires or clutch suck that at least gives you some time to get good ones.
Repairs: Fix the broken stuff, fix leaks/seals, replace all of the fluids, replace all of the filters, fix any bad wheel bearings, do a thorough tune up, replace the timing belt if it is in question, put the timing to 14-15deg advance (and run 89 or 93 octane), replace obviously rusty bolts and screws. Fix or remove the A/C and power steering systems.
Obviously you do these as you're doing other modifications if the same parts have to come off. I.E. The rear main seal, and input shaft seals, the drive shaft seal, clutch line, shifter boots and bushings, and the clutch slave cylinder would be done along with a clutch and flywheel job.
Plans for a finished Miata:
wheels/Tires. You want the widest tires that will fit on your wheel. The stock wheels are super light but very small and few good tires will fit on them. 195 series tires are the widest that you can fit on the stock wheel. The best wheel size for a miata is generally considered to be 15x7". Much better tires are available for this size and larger 01+ brakes fit in some wheel models. Lightweight wheels are essential on the miata so ideally you would get something that weighs as much, or less than the stock wheels(12.5lbs).
Chassis bracing: The FM butterfly brace is the first and best brace you should add to your miata if you don't have underbody damage. If you're doing a clutch/flywheel, an exhaust and maybe engine mounts, do those first so that you don't have to take the brace off again. A shock tower bar will reduce cowl shake and also makes for an easy spot to mount a brake master cylinder brace. A rollbar works wonders and saves your head in a crash. The factory hardtop helps stiffen things up and improves aerodynamics. There are subframe braces for front and rear from the factory, the front you can make out of a flat, rigid, piece of metal or a pipe, the rear is available on 92+ cars and from the aftermarket.
Mounts: engine and diff mounts.(Mazda motorsport, MMR, and function 7 all make hard or solid mounts). For better throttle response and shifting.
Suspension: The lower ball joints, upper control arms, bushings, and alignment bolts should all be done at the same time. upper shock mounts (NB, fatcat, or FM), shocks, and springs should be done at the same time and ideally when you're doing the ball joints etc. Then be sure to do an alignment immediately. Anti-roll bars and links can be done independently. The tie rods should be replaced if they're old, also before the alignment. Buy tie rods for the 93Le edition if you are lowering your car, its longer shank will correct your steering geometry and reduce bump steer. This is by far the best money spent on a Miata after the butterfly brace and a good set of tires.
Brakes: 1.8 brakes (94-2000), the carriers and rotors, are an upgrade for the 90-93 1.6 cars. The calipers are the same. Its probably a good idea to replace those too though since any original calipers are going to be quite old now. The 2001+ sport brakes or a BBK are a better upgrade if you have the right 15"(?) or larger wheels. Braided stainless lines, sport pads, high temp brake fluid, and quality rotors should be done at the same time. I recommend Porterfield R4S, Ferodo DS2500, or Hawk HP+ pads. The Ferodos and Hawks WILL squeak. A master cylinder brace is just about mandatory on this car for good feedback and a solid pedal.
Drivetrain: The stock clutch is vague and weak at best though is does have a nice light pedal with wonderfully short travel. An aftermarket clutch will be a noticeable improvement in engagement feel, holding power and durability. A stainless braided clutch line will help the clutch pedal feel more crisp. The best drivetrain modification is a light weight flywheel. First and second gear will feel far more powerful and downshifting becomes pure joy. I recommend the ACT hd Street clutch and fidanza flywheel.
NA Power: A quality Intake, header, high flow catalytic converter, and exhaust are the baseline of non-turbo power. It's not big power for the money but it makes the engine breath better helping throttle response and possibly gas mileage. Other effective power mods are cleaning and or adding engine grounds, a thorough tune up(plugs, wires, fuel filter, timing bump to 14-15 deg advance, new o2 sensor, clean the throttle body, etc etc), heat shielding around the header and the intake. Proper ducting for the intake and a free flowing air filter(i prefer a dry paper filter for maximum filtration ie apex'i or AEM).
Forced induction power: A Turbo kit, proper fueling, standalone ecu or tuning, if 1.6 - get the stronger 1.8 rear differential. A 2.5" or larger exhaust and a stronger clutch. Heat shielding on anything close to the turbo, an intercooler(and sprayer), ideally a Garrett GT series turbo. A larger radiator and an oil cooler. Larger brakes for the 1.6 cars definitely and for the 1.8 cars probably.
Aerodynamics: A functional front splitter at least and maybe a rear wing for high speed stability if you're doing track days.
Interface: Functional racing/sport seats, pedals (for heel toe), and the shift knob of your choice. Get the hella e-code head light units for much improved night driving.
If you manage to get all of that done, and executed well, you'll have a brilliant, razor sharp, little sports car! I plan to on one of these cars lol!