Transmissions always transmit engine power to driving wheels and adjust
output to motoring conditions. But todays performance must also be fuel-efficient
and environmentally responsible. Suzukis SECVT does all that, and more.
The Burgman 650, Suzuki's largest-displacement-engine scooter, is the worlds first two-wheel vehicle to feature the Suzuki Electrically-controlled Continuously Variable Transmission (SECVT). "We knew from the start that this pioneering big scooter must satisfy customer demand for environmental friendliness," said Shinobu Tsutsumikoshi, who led the SECVT's prototype development in Motorcycle Engineering Design Dept. III. "So we refined the already-efficient CVT system even further through integrated electronic control of both engine and transmission."
"Unlike the conventional centrifugal CVT using a rubber belt, the SECVT adjusts the CVT ratio by varying the drive-pulley diameter with an electric actuator motor," relates Kazutoshi Ohashi who led development of the SECVT control systems in Group I, Miyakoda R&D Centre. "The SECVT controller calculates the target engine revolution based on the vehicle speed and throttle position, and automatically adjusts the CVT ratio. Unlike conventional systems that adjust the CVT ratio only to the engine revolution, the SECVT's calculation is made with the throttle position the rider's acceleration choice also taken into consideration. That optimizes the CVT ratio for actual riding conditions."
Tsutsumikoshi and Ohashi have worked together for years, as a team integrating the brain (control systems) and the body (mechanical structure) with each other, explains Tsutsumikoshi.
As for the body, the SECVTs innovative high-performance Dry Hybrid Composite Belt consists of 204 pieces of H-shaped high-strength aluminium blocks which are embedded with a pair of heat-resistant rubber tension members and covered with resin. The exceptional durability enables the belt to be run dry without the power loss characteristic of an oil bath, yet it also keeps the SECVT system lightweight and compact.
The brain of this beauty , the SECVT, gives the Burgman 650 two fully automatic modes. The Normal mode delivers the optimum CVT ratio for minimum fuel consumption, and the Power mode enables higher CVT ratios for a sportier ride. Our SECVT tailors the setting to the riders style, said Tsutsumikoshi, but the system really delivers on hilly winding roads. Enhanced engine braking contributes to stable downhill runs, and the direct acceleration feel gives you the sheer pleasure of a sporty ride. As a result, this automatic-transmission scooter surprises and thrills with a faster, more pleasurable ride than a manual-transmission motorcycle.
Easy to operate, comfortable, practical traditional scooter attributes enhanced in the Burgman 650 by the pleasure of cruising, thanks primarily to the compact SECVT, a smart brain in a tough body.