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12A 1st Generation Street Performance Page

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    The OE 12A front disc brakes are pretty good on the '80+ cars. Forget the crummy wedge style brakes on the '79 cars. You can bolt on the '80 caliper and hanger, and the brake lines will even match, as the thread pitch is the same. '81+ cars have a differnt thread pitch than the earlier cars. The rear drums work pretty well, but these rear ends lack the limited slip differential of the '81+ GSL cars. These rears are bolt in items (you will need the parking brake cables, too). I can recommend the carbon/kevlar material Hawk HPS and Porterfield R4S, as well as the Axxis (the pad formerly known as Repco) Metalmaster pads for a little better fade resistance and more stopping power, but you must flush and bleed new fluid into your brakes often (at least once or twice per year). If you race, do it before each event. I like the Ford DOT 3 truck fluid, and if that's not available, I like the Castrol stuff.

    The GSL-SE has larger front and rear rotors, but requires considerable work to fit to a 12A car - but it is all essentially bolt in stuff. The '84/85 12A front rotors have larger inner bearings that they share with the GSL-SE. You will need the entire rear end, rotors and calipers to do the swap. Additionally, you will require the entire strut assembly, rotor, and caliper. You'll need the wheels also.Good luck on brake line adaptors if you fit these to early thread pitch cars.

    The later '84/5 lower valence panel has vents that work rather nicely for ducting air to the front brakes. Use a few feet of 3" hose and cut a way a litle of the plastic fender liner to duct air to the caliper area. This works if you spend time on a track.

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    Next to porting, there is no other power gain as cheap as a good exhaust. And you have to have the good exhaust to get good results with the porting. Rotary exhausts aren't cheap by any means. A rotary is also an incredibly noisy device, so expect a fair increase in noise if you plan to modify the system for performance. Also, cheap mufflers die fast when forced to deal with the extremely hot exhaust gas temperatures (>1600 degrees F).

    The OE manifolds on the '81+ cars are pretty decent. They have a high nickel content and are very durable, but combining the exhaust pulses that close to the port robs a little power at the expense of noise control. The early '79/80 thermal reactor ones stink and are incredibly heavy. A good header is well over $100 - let your wallet guide you. The complete Mindtrain systems are my favorite due to the non-use of the OE downpipe, but even a catback is about $400. The stock catalytic convertors seem to do most of the muffling in these systems, but are very restrictive and heavy. A high flow cat or a presilencer go a long way to improving performance. The precat is not really necessary with a modern hi flow monolithic cat, and will pass Federal emissions without it or hollowed out (they seem to self hollow out after so many miles anyway).

    The Mazdatrix/RB dual system is also a very nice setup and really wakes up the engine. They use a dual presilencer setup to control noise quite well.

    HAS Motorsports in Arizona makes a Spec RX7 mandrel bend race exhaust with a high flow convertor which works great if you adapt a Supertrapp or other easily repackable silencer to the end. It includes everything from the manifold back (except the muffler). With no muffler, you'll get about 93 db - too loud for the street.

    For you fabricators out there, you can make your own dual exhaust that will enhance your HP curve. Use 1 7/8" or 2" tubes from the dual outlet header all the way to the axle (about 113"), use a collector in front of the rear axle, and a Mindtrain or other huge tailipipe. Sure, it'll be loud, but your're going racing anyway, right? If you are using this as a streetcar, buy a couple silencer blanks from Mindtrain and use them as presilencers - one in each of the dual pipes. This makes a huge difference.

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    Sure, everyone wants a 13B. The Mazdatrix catalog very thoroughly outlines the parts needed to do the swap into the 12A car, so I won't reflect on it. The nicest of the 13B n/a motors is likely to be the '89.5-91. They have factory high compression rotors, a light flywheel and a larger throttlebody/revised dynamic chamber. The older four port ones are becoming quite rare.

    The 12A engines have minor differences which can be capitalized on to make for some neat performance increases without buying pricey competition rotors or light flywheels. The '79-82 cars have heavier engine rotors, the '79/80 cars have a 32lb, 215mm clutch flywheel, while the '81-2 have a 24 lb, 215mm clutch flywheel. The '83-85 cars have lighter rotors (by several ounces), but a 27 lb, 225mm clutch flywheel (and the stigma of the feeble water/oil cooler). If you choose to mix/match flywheels and rotors, the best bet is the '83-5 rotors and the '81/2 flywheel and front counterweight. These flywheels have a 215mm clutch as opposed to the 225mm later ones, so you will need to choose the correct pressure plate and disc. It is also essential to have the rotating assembly balanced (Roger Mandeville did mine - and this is my car's brush with greatness).

    Mazda Comp sells a rotor housing with factory large exhaust ports from the early 12As, but with a modern 12A casting surrounding it. No cheating if you are a racer! You won't fool veteran racers - the 12A Mazda has been around a long time and it will be quite obvious if you are cheating. Street porting works very well for a street driven car, but it really only works well with intake and exhaust mods. Attempts at more power should be taken in a system approach, not as a bolt on extravaganza. Keep this in mind. No sense having monster ports with a OE exhaust and carb.

    I do not very much like the OE Mazda water/oil coolers. The seemingly perpetual o-ring oil leakage and the marginal heat transfer capabilities make these things seem better off in the parts bin. They seem to work fine for a mostly stock engine, however, except for the darned o-ring leakage and the added complexity of coolant hoses (that like to rupture from oil soaking).

    The early '79-82 radiators are made to have the big air/oil cooler hanging below them, still within the shroud's influence. This is a nice bolt-on upgrade for a performance rotary. I have had good success with the oil cooler out in front of the later '83-5 radiator. You will have to fabricate oil lines, trim the radiator bracket, and fabricate brackets to hold the oil cooler to the radiator supports.

    Oil coolers - for you lunatics that overheat your oil, you can use two coolers in parallel, or an RX4 cooler in place of the single 12A one. The RX4 cooler has an extra row than the 12A cooler. The oil performs major cooling functions in the rotary, so a good heat shedding cooler is a necessity.

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    The OE Mazda electronic ignition is just fine for street use. The point ignitions on single distributor rotaries can be upgraded to the electronic ones quite easily by swapping the distributor and jumping the resistors. The ignitors do not need these. The stock Mazda coils are fine.

    I like NGK and Magnecor wires. They fit well, are relatively cheap, and work fine.

    The stock port 12A motors seem to like just a *little* bit of advance over the factory settings. Just a couple degrees. More than that invites disaster. Keep the lead/trail spread the same as factory (advance them as a whole, not individually).

    Spark plugs - all electronic ignition 12A cars should use the NGK BUR8EQ14 plug for lead and trail. I get these at the local Pep Boys for about $4 each. They don't last very long (5-10K), and the fact that they never get a nice cooling waft of air like a piston engine makes their job look pretty difficult. Be sure to use some anti-sieze on the plug threads or risk galling what can prove to be the world's most expensive plug threads. For my 12A racer, I use BUR9EQP plugs lead/trail (from the 3rd gen Rx7).

    More to come as I get around to it.

    Happy rotoring.....

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