American Honda Motor Co. Inc.Torrance, Calif.

Dec. 21, 2004
Multi Matic continuously variable transmission

To auto buffs, the automatic transmission has been a mixed bag. Sure there's convenience, but shifts aren't always smooth, gas consumption increases, and performance suffers. As a cure Honda has introduced a different route to the automatic-transmission experience, one providing convenience (and fun) without the sacrifices that car buffs have grudgingly accepted since the 1930s, when automatics entered the driving idiom. Honda's solution is the Multi Matic continuously variable transmission (CVT) that it designed for the 1996 Civic HX coupe. At the heart of the system is a unique metal drivebelt that connects two variable-ratio pulleys, which expand and contract, depending on load and engine speed. The CVT concept virtually eliminates all transmission gears and provides a uniquely smooth driving experience. Undaunted by the inability of others to successfully commercialize the CVT -- a Dutch firm tried as early as 1958 with a two-cylinder minicar -- Honda has developed a technically sophisticated design that can be teamed with a higher-output (115 hp) engine. Above all, Honda's Multi Matic CVT still provides the convenience -- but without the shifts, performance loss, or gas-consumption penalty of conventional automatics. The coupe with the new CVT is the only automatic-transmission-equipped vehicle ranked in the Environmental Protection Agency's (EPA) top-10 list of fuel-efficient models. In EPA measurements, the car, which comes with a 1.6-liter, 16-valve VTEC-E engine, gets 35 mpg in the city and 39 mpg on the highway. The VTEC-E system uses variable valve timing to improve low- and mid-range fuel efficiency without sacrificing high-rpm power. Regardless of the slope or condition of the road, the CVT allows the driver to experience smooth acceleration at all speeds without gear changes. Not only is the CVT smoother than traditional automatics with torque converters, there is less torque loss, says product-marketing manager Art Garner. "The design goal," he says, "is to provide the convenience of an automatic with the perform-ance and fuel economy of a manual transmission." Under heavy acceleration, the drive pulley widens, causing the elements on the steel drive belt to shift toward the pulley center. Meanwhile, the driven pulley becomes narrower, forcing the elements on the driven side to be pushed outward toward the outer diameter of the driven pulley. Changes in the pitch diameter produce the smooth, seamless gear-changing effect. By making the transmission pitch diameter on the input side smaller and the output side larger, the rotation speed is reduced, increasing the torque (low gear). If the input side diameter is made larger and the output side smaller, the torque decreases and speed increases (overdrive). Hydraulic pressure controls the pitch diameter of the pulleys.

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