Artigo 1

Mazda Miata

The Miata Development Story

By Norman H. Garret II in the book “Mazda Miata – Performance Handbook – 1998”

You almost had to be there to believe it. Mazda in the mid-1980s was riding high. Sales of RX-7s were topping 60,000 units per year. The 626 and 323 models were selling like mad. The trucks had a popular niche carved out for themselves. The yen was strong against the dollar. Mazda was running like an athlete-and looking to expand its position as the No. 3 Japanese automaker. Since 70 percent of its sales came from the North American market, the Hiroshima-based company decided to open a design studio in America, to staff it with some clever Americans, and hopefully to create some U.S.-specific automobiles.

One of the first ideas was to recreate the MGB. It had only been three years since that car had disappeared from the U.S. marketplace in 1980. In that final year, MG had sold 40,000 Bs, even though by that time it was heavy and outdated. The Triumph Spitfire was discontinued during the same period, and soon there were no British sports cars left in the U.S. market. It was ironic to the product planners at Mazda that the very cars that created the affordable sports car niche in this country were now extinct-and that this seemed to leave a wide opening for someone else.

Bob Hall at Mazda Research and Development (R~D) first understood that if MG could sell 40,000 lightweight sports cars in America per year, Mazda could easily sell that many. Mazda was one of the few manufacturers that knew how to make a profit on just 40,000 units, and Mazda had a proud front-engine, rearwheel-drive history to work from. Thus, the Miata concept was born, initially referred to as the P729 project.

The initial design phase went pretty quickly-basic layouts and shapes were decided upon within 12 months. Since there were no direct competitors (other than the upcoming midengined Toyota MR2 and Pontiac Fiero), a small Mazda sports car could be designed without constraints other than cost and market position. The RX-7 was moving upscale, leaving a nice little corner of the market for the Miata to have for itself. Thus, Mazda was free to optimize the Miata for the passionate few, rather than compromise its design for the mass-market appeal. Each design team member was a confirmed sports car nut. Among them, some 76 different sports cars had been owned, ranging from Austin-Healey Bugeye Sprites to Lamborghini Countachs. Designing a small sports car was simply a matter of each member suggesting his favorite feature of his favorite sports cars: a curvy hood; a short shifter with great feel; a twin-overhead-cam, four-cylinder engine (the rotary would have had the wrong character); a frontengine, rear-drive layout; and a convertible top, for sure. Item by item, examples of the best were brought to the table and studied for inclusion into the P729 project.

The soft top was modeled after the finest on the market, the Fiat 124 Spider's. The shifter was targeted to be the mix of a Jag E-type's "snick-snick" combined with the smoothness of a used BMW 7 series. The engine styling was inspired by the Alfa Romeo four-cylinders of the 1950s and 1960s. The exhaust note was tuned to mimic the MGB. And on and on. Without the need to carefully place the Miata in the marketplace, the P729 project designers had free rein to make each feature of the car fit the sports car ideal.

The styling was to be both classic and modern. Mazda wanted to evoke as much of the classic-car emotion as possible, but realized that some younger owners would be seeing the Miata as a totally new idea. Mazda designed the car so it would look two years old when it was introduced, and still look two years old when a decade had gone by. Tom Matano, the studio head, knew exactly how to accomplish this critical task. Aside from being one of the most skilled designers on the planet, he understood the process, both politically and mechanically, to get the Miata to where it needed to be. Without him the Miata would be a very different car, and probably a less appealing one, if it were to exist at all.

The goals were simple to define, but difficult to follow through with. In practice, designing a lightweight sports car for the U.S. market in today's regulated automotive world is a great feat, especially because of government-mandated or market-demanded necessities such as 30-mile-per-hour crash tests, 50,000-mile emission warranties, 36-month bumper-to bumper component warranties, and so on. Fortunately, Mazda put enough engineering might behind the task and kept the cost-cutters at bay while staying true to the project's underlying goal. The Miata's package is a study in engineering density. In a large sport car, such as a Corvette, packaging all the necessary hardware is difficult enough. Trying to do the same in a sports car with a smaller chassis throws compromises at the designers right and left. Fuel tanks, catalytic converters, spare tires, heating and air conditioning systems, and others all become very difficult to fit into a small package. Keeping the "sports car" soul alive is sometimes impossible (for examples of failure, look at the latest Ford Capri or the Honda Del Sol).

The end result of the Mazda's efforts on the Miata package was a lightweight sports car (2,182 pounds) with a willing engine (116 horsepower) that had a perfect frontto-rear 50/50 weight balance when the driver was in place, had rear-wheel drive, and a simple convertible top, that sold for $13,500 when it was introduced in July 1989 as a 1990 model.

Since that time, more than 450,000 Miatas have been sold worldwide-nearly half in the United States alone. It has spawned the world's largest single-model car club and has set dass lap records at nearly every race track around the globe.

While many owners simply buy their Miatas for Sunday drives, most use them for daily commutes and weekend racing or touring. The cars have proven to be nearly bulletproof, with no single item showing up as a catastrophic weak spot.

As a sports car, it's been an unqualified hit-and as a basis for further modification, it's nearly unparalleled in today's market. From springs and sway bars to turbochargers and superchargers, just about anything that could be added to a car is available for the Miata to personalize and customize it from stock.

After the Miata had been on the market for nine years, Mazda updated the line with a new car for model year 1999. The core principles still apply: lightweight, affordable, well engineered, fun. The formula will play itself all over again as the sports car market flocks to its favorite poster child: the Mazda Miata.

Miata Engineering Details

To appreciate the Miata fully, you have to go beyond the stylish exterior and peer beneath the surface. While the shape is certainly pleasant to look at, the engineers were sworn to the ideal that the car should drive as well as it looked.

There was a phrase posted on the wall of the engineering department that told the story of how the Miata was to feel on the road: "Oneness between horse and rider." To create this "oneness," some critical decisions needed to be made up front. Mazda was committed to reducing the weight in all of its cars and had made great advances in the science of building lightweight automobiles. At this time, Mazda's R~D budget was greater than that of Porsche, Mercedes, and BMW combined, so some heavy artillery was aimed at all the many engineering challenges that stood between the blank drawing board the P729 project engineers started with and the ideal sports car the Miata would become.

The first challenge came from the chassis department: A convertible has to be strong to prevent unwanted vibration. The Miata was one of the first cars to use computer modeling for the entire structure, resulting in a much lighter and stronger body-chassis assembly than that of any previous convertible. Strength was put in just the right places (front and rear bulkheads, door sills, and so on) to create a firm foundation for the suspension to work from. To reduce the final weight further, the project engineers liberally used plastics and aluminum. One of the largest front body panels, the hood, has an aluminum skin for light weight (just as many British sports cars did, including the MGA). To further reduce weight at the extremities, plastics were used in the bumper cores.

When it came time to choose the suspension design, a classical approach was tried. Up to that time the Japanese auto industry had been on a patent binge, creating more and more complicated systems to solve problems. This trend was reversed on the Miata, as Mazda went to the old school of double-wishbone suspensions both front and rear. These had been the choice of great sports cars for years and would provide the optimum camber patterns during cornering.

Then the decision was made to rigidly connect the engine-transmission assembly to the rear differential. This brought a few different benefits: The typical drivetrain windup and release during on-off throttle maneuvers would be greatly reduced, the total powertrain structure would be much more rigid, and the assembly time could be reduced. This type of torque-tube powertrain structure was previously the province of considerably more expensive sports cars, such as the Ferrari Daytona, the Porsche 928, and even the C4 (and now C5) Corvette.

The engine itself started life as a standard 1.6-liter fourcylinder used in the Mazda 323, but it received a number of improvements, thanks to the capable hot-rodders in Mazda's engine department. (Remember, these were the guys that got the rotary engine to work.) The rotating masses (crankshaft, rods, pistons) were lightened to improve throttle response. The compression ratio was raised to 9.4:1 for more power across the rpm range. A windage tray was added to the aluminum oil sump to reduce drag on the crankshaft from frothing oil. The four-valve cylinder head was ported for optimum horsepower and torque, and the camshafts were aggressively shaped to maximize flow at high rpm (and, on the 1.8-liter engine, they were made hollow for lower weight). As a result, the Miata 1.6-liter engine created 116 horsepower at 6,500 rpm and 110 pounds-feet of torque at 5,500 rpm-that's 72.5 horsepower per liter, pretty respectable for a factory production effort. As a historical, nonemission legal comparison, an MGB at its best made 50.2 horsepower per liter; an Alfa Romeo 2000 2.0L four-cylinder DOHC engine produced 61.0 horsepower per liter (19731 988); and a 1 963 Jaguar XKE engine (DOHC 3.8L) produced 70.1 horsepower per liter.

Multiport fuel injection was used to maximize power and decrease emissions, rather than a less-expensive throttle-body injection system. Carefully designed intake-tract resonance chambers were used to accentuate low-end torque. A tubular, low-restriction stainless-steel exhaust header was created, and the downstream system was treated to a high-flow catalytic converter and a well-tuned muffler. In fact, great care was taken with the exhaust note so that the Miata could be instantly recognized as a classic sports car.

The engine tuning followed a scheme to maximize power while giving an ever-increasing sense of acceleration. This makes the Miata fun to drive and gives the driver the impression of more power than is actually there. The rate of acceleration has a subtle increase to it, leading to a "sinking into the seat" feeling as you go up the rev range in a particular gear. This acceleration-of-acceleration is called "jerk" in engineering terms, and is used in the Miata to make it all the more entertaining. To quote David E. Davis of Automobile magazine, "I have never driven a Miata and come away wishing for more power, but every time I drive a Z3, I find myself hankering for additional horsepower." The two cars have similar power outputs (although the Z3 is 400 pounds heavier), but the torque and gear ratios of the Miata are matched to optimize driving pleasure.

In the overall picture, the Miata drivetrain has a definite Alfa Romeo influence in engine theory, even down to the cam-cover styling. But at the core of the system is a rock-solid piece of Japanese engineering that's proven itself well over the last nine years. Even after nearly a decade of heavy racing campaigns, the Miata is regarded as a long-lived machine. Owners regularly pass the 200,000-mile mark, and racers go season upon season without a major failure.

In the rest of the drivetrain, the gearshift is of special note. The goal was to have the smallest shift pattern and lowest shift effort possible. The end result is the most acclaimed shift mechanism in today's market. Mated to the gearshift is a close-ratio transmission that's well matched to the engine's torque curve. At the back end, a limited-slip differential using viscous couplings was optional for superior traction during sharp cornering and acceleration. Later, a Torsen differential was made available starting with the 1994 model year. These are the state-of-the-art limited slip differentials that use a complicated gear set to equalize rear-wheel torque and provide smoother and stronger power transmission than typical clutch-pack or viscous clutch differentials.

As the starting point of a project sports car, the Miata is unmatched in reliability, tuneability, and the availability of factory and aftermarket parts. With just a little care and money, any Miata can be made into the sports car of your dreams, be it a weekend racer or a super-hot street car. You're only limited by your budget and your imagination.

Stock Performance Values

Right off the showroom floor, the Mlata is a great performer. Cornering, road feel, overall handling, and even acceleration are all excellent for the small sports car niche it falls into (or has reinvented). Here's a summary of how a stock Miata can perform, both in its 1.6-liter (1989-1993) and 1.8-liter (1994-on) forms:

Miata 1.6 liter:

Acceleration, 0-60 miles per hour: 9.1 seconds

1/4-mile acceleration time: 17.0 seconds at 81 miles per hour Top speed: 112 miles per hour

Braking, 60-0 miles per hour: 137 feet Cornering force: 0.87 G on standard tires

Slalom speed (Road ~t Track magazine): 62.4 mi es per hour Weight: 2,182 pounds

Weight distribution /with driver in carj, frnnt/rear: 50/50

Miata 1.8 liter:

Acceieration, 0-60 miles per hour: 8.4 seeonds

retorna para pagina anterior