Mazda RX-7

In 1969 Mazda Project engineer Akio Uchiyama began work on a two-seater sports car. Internally it was called project X020A and eventually became known as RS-X. The idea was to share a chassis from a production saloon, thus saving on production costs and limiting the time-to-market. This project continued until 1973, when the oil crisis finally put an end to the car.

Around 1975 Sinpei Hanaoka, a Mazda board member and former banker, recommended that a rotary-engined sports car be developed. Soon after, Project X605 began. This was different from the prior attempt in that a new chassis was developed for the sole purpose of accommodating the rotary engine's compact dimensions. Akio was tasked with assisting Sumio Mochizuki, the Chief Project Engineer, in designing the chassis. Styling was handled by Yasuji Oda and Matasaburo Maeda. The creation of the rotary engine design was given to Kenichi Yamamoto.

The rotary engine was compact and small and helped in the 50/50 weight distribution resulting in exceptional handling. Instead of focusing on maximum horsepower, a fuel-efficient 12A version was opted chosen. The engine was placed in the front and designed to power the rear wheels. To reduce production costs, the suspension was borrowed from the production vehicles. The front had McPherson struts and coil springs, and the rear was a live axle with coil springs. The steering was a re-circulating ball. Disc brakes were placed in the front while the rear brakes were drums. The chassis was comprised of monocoque, which helped reduce weight while increasing structural rigidity. The rear window was originally a one-piece wraparound sheet but was replaced in favor of a cheaper and more reliable 3-piece design. During wind tunnel testing, it was revealed that the design had an excellent aerodynamic drag, equivalent to a Porsche 924. With the headlights exposed, the drag was reduced from 0.36 to 0.38 CD, similar to the Datsun 280Z.

Three transmissions were available; a three-speed automatic, four- and five-speed manual.

The 12A rotary engine, with the help of modifications, was able to produce five extra horsepower and three more pound-feet of torque. Fuel injection was attempted but did not work with the exhaust thermal reactor and would not have complied with United States safety and emission regulations. A characteristic of the engine is that it is very quiet. It is smooth and 'torqy' offering loads of performance.

The front seats were buckets with plaid designs and the rear was a bench seat. The instrument panel featured a 130 mph speedometer. The rev counter had dual purposes, first, it reported revolutions per minute and when the ignition was on but the engine had not yet started, it served as a voltmeter. This was later changed to separate gauges.

In 1977 the prototype was finished and a year later, in March 1978, the RX7's were being produced at the Ujina plant. The RX-7 was introduced to the members of the press at Hiroshima and later debuted to the United States in April 1978. The RX7, a.k.a. Project X605 was an immediate hit.

The Mazda RX7 was a practical sports car, highly competitive, and offered at a low price. Supply could not keep up with demand and many potential buyers were often offering more money above sticker price just to own one. There were initial quality problems, but all issues were quickly resolved. By 1980 nearly 140,000 examples had been produced. Using a 12A rotary engine displacing 1.2 liters, it was capable of producing around 105 horsepower. Zero to sixty was accomplished in ten seconds.

In 1984 a more powerful 1.3-liter rotary engine was introduced, the 13B. The 13B produced 135 horsepower and was placed in the 'special edition' cars called the GSL-SE. The GSL-SE were given disc brakes on all four corners and a Limited Slip Differential. The zero to sixty time improved to just under nine seconds.

The main complaint about the car was its steering. Many believed that the recirculation ball should be replaced with a rack-and-pinion unit which could better keep up with the car's excellent performance and offer superior handling. Besides this, the car was given excellent reviews by all automotive magazines.

The RX7 was eligible for class C racing in the United States. Under IMSA's classification, it was eligible for 2.5-liter racing. After its domination on the racing circuit, the IMSA re-classified the RX7 at a higher minimum weight limit which allowed it to run in the more competitive GTX class.

The RX7 production continued until 1986. As time progressed and as a byproduct of racing, the RX-7 had been much improved. However, the field of affordable sports cars was increasing, and the RX-7 was in need of a replacement.

The Second Generation RX7

Chief Project Engineer Akio Uchiyama had traveled to the United States to become better acquainted with the demands of the RX-7's largest market. His interviews and the comments and suggestions received from the owners and prospective owners influenced the design of the second series of the RX-7.

By June 1981, the project was started. Akio Uchiyama chose the name P747 to represent this task. Various designs were created, each targeting different markets. The designs were labeled 'Realistic Sports Car', 'Technologically Advanced Sports Car', and a 'Civilised Sports Car'. The designs ranged from a hard-core sports car to designs that offered plush amenities and hints at its sporty roots. The price of these potential cars was estimated to fall between $9000 through $13000, depending on the design chosen. In total, there were around twenty designs created, each representing different ideas of the next generation RX7. Two designs were chosen as 'favorites' and full-size clay models were developed and shown to consumers.

By February 1983, a design was chosen. Takashi Ono was tasked with designing and building the exterior of the vehicle. Most of the demands made by Ono were carried through but a few needed to be redesigned based on consumer reaction and to accommodate mechanical components. The resulting prototypes achieved a 0.29 CD of aerodynamic efficiency. This was the result of a low hood and a 63.5-degree angle windshield.

Jiro Maebayshi was tasked with designing the suspension. The resulting mechanics were borrowed from a truck suspension created by Takao Kijima. The front and rear suspensions were independent with the front incorporating McPherson struts. To make the car more maneuverable, four-wheel steering was experimented with but unfortunately, the results were not promising. Instead, a system was adopted that allowed a small degree of rear steer to be created by the rear suspension during cornering. The rear wheels would steer in the same direction as the front increasing stability at high speeds. At low speeds, the rear wheels would steer in the opposite direction of the front wheels. The system was dubbed the 'Dynamic Tracking System Suspension' and 'Triaxial Floating Hub'. The system did increase noise so to compensate the final drive system and rear suspension were mounted separately on the rear subframe. To reduce the noise caused by the subframe and the chassis, Rubber bushings were used. The rack-and-pinion steering and the updated suspension addressed the major pitfall of the first-generation RX-7.

The second generation came with options, such as brake sizes and wheels. Standard was 9.8-inch ventilated disc brakes with the 10.3-inch disc with single-piston floating iron calipers offered as optional equipment. The anti-lock braking system was not offered at the introduction of the vehicle but became available at a later date. The RX-7 could be purchased with a five-speed manual or a four-speed automatic transmission. A turbocharger system increased torque by nearly 30 percent.

A luxury version was offered, outfitted with cruise control, air conditioning, leather seats, power windows, and a security system.

The 13B engine had been introduced in the first generation RX-7. It produced 135 horsepower, and by reshaping the plenum, 11 extra horsepower was achieved. The plenum was curved again for the P747 to increase the power even further. Other modifications included the addition of a second fuel injection, a new rotor apex seal, a digitally controlled Bosch L-Jetronic, a larger air cleaner, and wider throttle intake and valves. Through these and other efforts, more horsepower and better fuel economy were achieved, and the engine became more durable. In the end, the engine produced nearly 150 horsepower and 138 foot-pounds of torque. This meant the vehicle could propel from zero to sixty in just eight seconds, and top speed was achieved at nearly 130 mph. The turbocharged 13B version was rated at 182 horsepower and 183 foot-pounds of torque. The fuel economy was nearly identical to the non-turbocharged version, 17 city, and 23 highway.

The interior was convenient, ergonomic, and modern. There were orange instrument needles, red lettering, an 8000 RPM tachometer, four auxiliary dials for oil pressure, battery charge, fuel level, and coolant temperature. The turbocharged versions had a boost gauge in place of the battery charge.

The RX-7 was offered in two-seater and 2+2 configurations, however, the rear seats were small and were best used for luggage rather than transporting extra passengers.

After the design and development of the prototype P747 and before official approval to begin mass development the P747 ran into a problem. The United States would enforce a tax on all vehicles that weighed over 2875 pounds and did not meet a 22 mpg combined city/highway rating. P747 was too heavy and did not meet the combined gas rating and nearing the point where the project would be discontinued. Upper management allowed one month to reduce the weight and to improve fuel economy.

Every designer and engineer began removing items, replacing others with a lighter material, and searching for ways to reduce the weight. The cast iron wheel hubs were replaced with alloy and the spare tire jack was replaced with an aluminum unit. The final drive cover was replaced with an aluminum material and the suspension arms became forged aluminum. The weight-saving measures continued and in the end, P747 weighed 2630 pounds, still a hundred pounds more than the first generation RX7 but it did include many mechanical and electrical improvements and features. The major downside to using the lightweight material was that it was more expensive than the steel that it replaced.

The name RX-7 was retained, although many believed that it would have been given the name RX-8, the next logical succession in the Mazda naming convention.

Introduced in 1986, it was immediately successful. Sales were strong and higher than any other year for the RX-7. The 13B 1.3-liter rotary engine producing 146 horsepower was standard as were the four-wheel disc brakes. The turbo version named the 'Turbo II' increased the horsepower to 182 horsepower. Zero to sixty was achieved in 6.8 seconds in the turbocharged version while the naturally aspirated engines achieved 60 mph in 7.7 seconds.
For 1987 sales slowed but this was expected. Improvements were added, defects were fixed, and the RX-7 continued to evolve. The luxury and turbo versions were outfitted with antilock brakes as standard equipment. A convertible option became available from the factory. The rear window was made of glass and had a defrost mechanism built in. In America, the Convertible option came with a naturally aspirated engine and a manual gearbox. Anything more and the car would have been too heavy, qualifying for the Gas Guzzler Tax. In other countries, the RX-7 Convertible could be purchased with the Turbo and other optional equipment.

Throughout the years, Mazda introduced various specialty versions to commemorate special occasions, offer an exclusive line-up, and improve sales. A Tenth Anniversary special edition honored the ten years of production for the RX-7.

By the close of the 1980's, the 13B naturally aspirated engine had been improved to produce 160 horsepower, the turbo version producing as high as 200 horsepower. The axle and gear ratios were improved to handle the increase in power. The gear shift mechanism was changed in favor of a shorter-throw unit. Steering was improved through the use of engine speed sensing instead of the prior speed-sensing steering.

In 1989 the Mazda Miata was introduced, revitalizing sales for the small, simple, two-seater sports car market. Many believe it stole sales away from the RX-7, which for 1990 saw sales slowing down. The RX-7 was still the choice for sports car performance while the Miata became the cheap sports car option.

By 1992 the production of the second-generation RX-7 had come to an end. 1990 was the final year for the GXL 2+2 hatchback. From 1991 onward, all Mazda RX-7's were two-seaters. Since the redesigned 1993 RX-7 model was introduced early, there were no official 1992 RX-7's.

The Third Generation RX7

Debuted in 1993, the third-generation Mazda RX-7 was available only as a two-door hatchback. Under the hood was a new twin-sequential turbocharged 13B-REW rotary engine producing an astonishing 255 horsepower. A five-speed manual and four-speed automatic were offered. On all four corners were Anti-Lock disc brakes. Safety was improved with the introduction of a driver-side airbag.

Weighing 190 pounds less than its predecessor and offering 50/50 weight distribution, the powerful and redesigned third-generation RX-7 was a performance machine.

The RX-7 was offered with two packages that could not be combined. The first was the R-1 designed for those searching for the ultimate performance from their RX-7. The package added body spoilers and dual oil coolers. The Touring Package was offered for those seeking luxury from their sports car. This package added leather seats, Bose speakers, steering wheel-mounted cruise control, and a power sunroof.

In 1994 safety was enhanced with the addition of a passenger-side airbag. Map pockets and a revised dashboard were also new for 1994. The performance package was now called the R-2. A new package was offered called the Popular Equipment package. This included a power sunroof, rear cargo cover, and leather seats.

Compared to the prior versions, the third-generation RX-7 was short-lived. Its performance, handling, low weight, and styling continued the legacy established by the first and second generations. The downfall for the third-generation RX-7 was its sticker price costing over $35,000 in 1995. 1995 would be the last year the RX-7 was produced. Ending a legacy and bringing to an end the production of the rotary engine, at least for a while. With the introduction of the Rx8, the rotary engine has been reintroduced. A new chapter is beginning.

By Daniel Vaughan | Sep 2007