Promises to Keep: 2006 Mazda Miata MX-5

Promises to Keep: 2006 Mazda Miata MX-5
Overhead Front Drivers Side View

The basic layout-a front/midship engine location driving the rear wheels-continues. The engine, transmission, and differential are linked by an aluminum beam and a stiff driveshaft to sharpen throttle response. As previewed by the 2003 Tokyo show Ibuki concept, the engine itself has been moved rearward by 5.3 inches to reduce the yaw inertia and achieve near 50/50 front-to-rear weight distribution. Naturally, all-independent suspension returns, with control arms at the front and a multilink setup at the rear. (It's amusing to consider the indignant outcry that would result if Mazda got cheap and went with a live rear axle.) As before, a light but stiff unibody forms the foundation for the Miata's natural, nimble dynamic character. Per Miata tradition, engineers paid particular attention to harmonizing steering, suspension, braking, engine, and transmission responses into a coherent whole. The front track was increased by three inches, and available footwear has grown to seventeen inches in diameter. Underhood, the strut-tower brace now is triangulated, linking up to the fire wall for additional torsional stiffness. The front frame rails, the roll-bar structure, the A-pillars, and the underfloor and rocker panels are composed of ultrahigh-strength steel, while the center spine, the frame rails near the fire wall, the rear wheel wells, the rear fire wall, and the door openings use high-strength steel. The result is a unibody that is 22 percent stiffer in bending and 47 percent stiffer in torsion compared with the current MX-5.

Interior View Steering Wheel

The first two MX-5 generations were Coke-bottle-shaped, but the new car, when viewed from above, forms more of an oval, with narrower front and rear sections but extended shoulders, an architecture that also was previewed by the Ibuki. In real terms, this results in more hip, shoulder, and elbow room, as the new car is about an inch and a half longer and wider and half an inch taller, with a wheelbase that is 2.6 inches longer. Bigger usually means heavier, but R&D chief Joe Bakaj promises that the new roadster is "within 22 pounds of the current car," which weighs about 2440 pounds. Any opportunities to trim excess avoirdupois, no matter how minute, were seized, including using aluminum for the hood, trunk lid, various suspension components, and rear brake calipers, plus composite plastics for the intake manifold and camshaft cover. The power steering pump and the air-conditioning compressor are mounted directly to the aluminum engine block, saving the need for seven pounds' worth of separate brackets. A hollow tube in place of a solid rod for the front anti-roll bar saves another five pounds. And so on. So painstaking were Mazda engineers' efforts to save weight that drivers and passengers might feel obliged to go on a crash diet before driving the MX-5, lest they negate all the clever weight-loss engineering with their own bloated bodies.

If you were hoping for a rotary in the new roadster, you will be disappointed, but we think Mazda is wise to reserve that idiosyncratic, gas-guzzling, oil-consuming engine for the RX-8. Instead, we get a new 2.0-liter, DOHC four-cylinder in place of the previous 1.8-liter engine, a choice of five-speed or six-speed manual transmissions, and the option of a six-speed automatic with steering-wheel-mounted paddles. With a 10.8:1 compression ratio, variable intake valve timing, electronic throttle control, and a high, flat torque curve, this unit produces 170 hp-the same as the upcoming Pontiac Solstice-at 6700 rpm and 136 lb-ft of torque at 5000 rpm, compared with 142 hp at 7000 rpm and 125 lb-ft at 5000 rpm in the current car. The engine is slanted 10 degrees to accommodate a large, dual-mode intake manifold. Powertrain engineer Tetsuo Fujitomi boasts that the new engine will, above all, be livelier and more linear, with "constant acceleration feel and powerful, torqueful, smooth response." As before, MX-5 engineers carefully tuned the engine and exhaust for optimal sound characteristics, concentrating on smoothness at lower rpm and rising to a more resonant, sporty song as the engine races to its 6700-rpm redline.

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