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1990 Mazda Miata Turbo - The Funky "Minimonster"

It Might Be A Girl's Car But This One Blasts 10s On Street Tires

Robert Choo
Sep 1, 2001
Photographer: Gary Castillo
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Turp_0109_01_z+1990_mazda_miata_turbo+front_right Photo 1/14   |   10.98 @ 125 mph

The funky purple Miata that's plastered on these pages is owned by Ric Stephens. Remember his name now, since you will be hearing a lot of it in the future. We first spotted Stephens (obviously hard to miss with a purple Miata), at the Lone Star Nationals, competing in the Street Class. As he pulled up to the line, we thought nothing much of the Mazda other than thinking to ourselves "this must be a joke, right?" A Miata trying to compete in a class dominated by Supra twin-turbos and RX-7 twin-turbos, no-way? Well, the Miata sure showed us. As the lights flashed green, the roadster left with a fury, squatting hard off the line and laying down two dark strips of molten rubber on the asphalt. Our jaws dropped in amazement as the clock down the 1320 clicked on, 11.48 at 122 mph. Stephens would later better that time with a 10.98 at 125.59 mph during exhibition rounds. We later caught up with Stephens for a Q&A session and, of course, a date with the camera.

Turp_0109_03_z+1990_mazda_miata_turbo+garrett_turbo Photo 2/14   |   Main power production comes by the way of a turbocharger.com T4/T3 hybrid hairdryer that is capable of producing 25-plus psi.

As Stephens popped the hood of the Miata, we were expecting to see a rotary powerplant under the bonnet. But to our surprise, the Minimonster was still powered the factory four-cylinder Miata engine. Stephens told us the engine was completely stock with the exception of some mild port and polish work performed by No Limit Motorsports. Other than that, the engine is a bone-stock 1.8-liter engine found in 1994-up Miatas. We asked, bone-stock? He answered with authority, "that's right bone-stock." He also added that the block has never been apart, stock rods, stock pistons, stock crank, stock cams, stock valves, stock springs, stock everything... and the power of a turbo.

As the conversation continued, we found out Stephens was no stranger to import performance. He has owned three second-gen RX-7s (two turbo and one non-turbo), an '84 626 turbo, '88 MX-6 turbo and '88 Mazda 323 GTX. He originally started, like many of us, competing at the street races with his '88 MX-6 turbo, which did very well, he added. He would soon have the urge to go faster, seeing the limitation of the front-drive MX-6 and seeking a more professional image, he sat down with his prime fabricator at the time Corky Bell to discuss a game plan. In order to pursue his racing interests, he would have to sell his most prized possession, the MX-6 to his good friend in order to come up with the money needed to build a race vehicle. Two weeks later, Stephens would purchase a 1990 Mazda Miata for $3,000 (don't ask us, we still can't figure out why a Miata for a racecar). With the keys to his newly acquired Miata in hand, Stephens headed to Corky Bell's office to put their gameplan in motion. The two brainstormed and came to the conclusion that the factory 1.6-liter engine would have to be replaced with the larger 1.8-liter displacement Miata engine. Stephens combed the local junkyards and found a complete 1.8-liter engine for $750. Wasting no time at all, the 1.6-liter engine was yanked out and the new 1.8-liter found its way into the engine bay.

After the engine was installed, a custom Corky Bell turbo kit was fabricated for the Miata. The turbo kit is a one-off custom kit that Stephens designed himself using custom parts. The cast turbo manifold is a Corky Bell unit, which has been reworked by Stephens to achieve better flow characteristics. Mounted to the manifold is a custom turbocharger.com T4/T3 hybrid hairdryer capable of producing more than 25 psi of atmospheric pressure. An HKS EVC IV boost controller and Corky Bell wastegate handle boost control duties. From the turbo, spent gases are expelled from the turbo housing via a custom Thunder Fabrication 3-inch downpipe exiting through a 3-inch Ultra Flow canister. On the compressor side, boost pressure is routed through 2 1/2-inch mild-steel I/C piping to a custom Corky Bell front-mount intercooler. After ample chilling, the charge air is then force fed into the port-matched intake manifold.

Turp_0109_08_z+1990_mazda_miata_turbo+hks_bov Photo 8/14   |   To prevent boost pressure from falling between gears, an HKS blow-off valve releases back-pedaling pressure to prevent it from slowing down the turbo.

Once the charge air enters the combustion chamber, 550cc squirters from RC Engineering inject high-octane juice to the mix. Ensuring all injectors receive their fair share of juice, a high-flow in-tank pump transfers fuel from the tank to a custom Vishnu high-flow fuel rail. Factory bumpsticks orchestrate valvetrain operation. The 9.0:1 compression factory cast pistons then further compress the mixture in the chamber. As the compression stroke nears the end of its cycle, the NGK plugs ignite the mixture, causing a violent explosion to send the piston downward onto its power stroke.

Wanting to extract the full power potential from the turbo engine, Stephens realized the best method was to employ a complete stand-alone engine control unit. Wanting to use the direct-fire coil set-up originally found on the Miata, Stephens called upon Electromotive for a complete engine management system. Since Stephens was a novice when it comes to the Electromotive system, Fred at Electromotive recommended a TEC-II unit capable of controlling fuel and ignition maps. The unit also comes equipped with the high-energy direct-fire coil set-up that Stephens was searching for. Having never installed a TEC system before, Fred and fellow TEC and Miata owner Barry Birdwell helped Stephens through the installation phases. Once running, Birdwell gave Stephens a crash course in tuning, which was crucial in keeping the factory engine alive. With Birdwell's tips and help, Stephens was able to extract 399.4 hp and 375 lbs-ft of torque at 25 psi of boost pressure-all this from an internally stock factory 1.8-liter engine! Novice or not, 400 to the wheels is getting it done!

Stephens knew that making power out of the Miata was going to be the easy part, getting it to the ground through D.O.T.-approved drag radials would be a totally different story. Transferring the power from the crankshaft to the transmission is a factory 1.8-liter flywheel, which he chose for the larger surface area (215mm vs. 200mm 1.6-liter flywheel) to contain the harsh torque of clutch engagement. The clutch Stephens selected was an ACT unit using the company's Extreme pressure plate with a six-puck race disc. Knowing the factory driveline was the weak link, Stephens upgraded the factory driveshaft, rear-end and drive axles. Providing the tire patch are a pair of 225/50-15 BFGoodrich D.O.T. drag radials mounted on lightweight Enkei aluminum. Suspension travel was addressed with Tokico five-way adjustable Illumina shocks tag-teamed with stock springs allowing Stephens to set up the suspension to meet track conditions.

Although the Mazda is capable of clicking off 10-second e.t.s, Stephens noted that the Miata was built on a strict budget and remains fully streetable in its 10-second trim. Stephens spent $15,000 on his race Miata over a period of two years. Some might think this a lot of money, but the price tag also includes the car's purchase price. We know of some people who spend that much on just the engine and turbo combo alone. When we last spoke to Stephens, he said the stock engine is on its last leg and that he is going to build the engine for more power and totally redesign the turbo system. If you are looking for Miata power, you might want to check out his Web site at www.racingmazda.com. Street Class racers beware, because this Minimonster is on a rampage and you're in its path.

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Sources

BFGoodrich
877-788-8899
www.bfgoodrichtires.com
RC Engineering
Torrance, CA 90501
310-320-2273
http://www.rceng.com
Electromotive
Manassas, VA 20110
703-331-0100
http://www.electromotive-inc.com
Advanced Clutch Technology (ACT)
Lancaster, CA 93535
Enkei Wheels
Roanoke, TX 76262
817-490-5600
http://www.enkei.com
By Robert Choo
118 Articles

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