TOKYO - Some of the slickest powertrain technology at the Tokyo Motor Show wasn't in the glare of the klieg lights.
For example, no slinky models hovered over the low-cost fuel-injection systems shown by Honda Motor Co. and others for four-stroke, 50cc motor scooters. Yet the motorcycle industry's steady migration away from oil-burning two-stroke engines could do more to cut urban air pollution in scooter-dependent Asia than any single advance since the catalytic converter.
The parade of nifty powertrain technology carried over to the automotive halls, where several companies displayed their gizmos for making vehicles cleaner and more efficient.
Chevrolet Triax: Only those who climbed the stairs to a secluded platform above General Motors' stand found this unique gasoline-electric hybrid concept. The Triax powertrain was shown in three types: gasoline, gasoline-electric and pure electric. The gasoline version uses a turbocharged 1.0-liter double-overhead camshaft four-cylinder engine built by Suzuki Motor Corp. to return 35 mpg in the Japanese government's fuel economy test.
The hybrid teams the 100-hp Suzuki engine with a 50-hp electric flywheel motor sandwiched between the engine block and the Suzuki-built continuously variable transmission. When the vehicle stops, the engine shuts down, but the motor automatically decouples and continues to run accessories such as the air conditioning compressor.
The pure-electric AWD Triax featured a pair of GM's prototype third-generation electric drive units on each axle. Compared with the second-generation motors found in the EV-1 electric car, the 50-hp Gen III motors are lighter and more efficient. GM claims a range of 165 miles using nickel-metal-hydride batteries.
Mazda Renesis engine: Mazda Motor Corp.'s trademark rotary engine has undergone extensive surgery to attack its worst ills: high fuel consumption and poor emissions. Mazda moved the exhaust port in each chamber from the area swept by the tip of the triangular rotor to the area swept by the flat of the rotor.
Previously, both the intake and exhaust ports were exposed for a brief period during the rotor's revolution. This overlap allowed some unburned fuel to escape down the exhaust pipe and some exhaust gas to contaminate the mixture, increasing emissions and reducing power. The change also allowed engineers to enlarge the intake port by 30 percent, improving the engine's breathing.
Mazda has known about the fix for decades, but cited improved sealing and lubrication technology for making it possible only now.
Subaru flat six: The new engine that will debut in the 2001 Subaru Legacy Outback was hiding in the corner of Fuji Heavy Industries Ltd.'s stand. It is an all-new DOHC 3.0-liter six cylinder that makes 'over 200 horsepower,' Subaru says.
The horizontally opposed cylinders are arrayed like the company's current four-cylinder boxer engines, but the new six is only 0.8 of an inch longer than the current four. Subaru also showed a prototype four based on the new six that is 3.2 inches shorter than Subaru's current engine.
Daihatsu Storia: This Toyota Motor Corp. subsidiary known for its minicars staged a technological tour de force. Notable hardware included a 1.0-liter, two-stroke diesel engine with variable valve timing and a unique scavenging system.
A supercharger and variable-vane turbocharger work in series to keep intake pre-chambers flanking each cylinder pressurized. The air rushes in as the sinking piston exposes the chamber ports, then is compressed and mixed with fuel from the injector. Four titanium valves at the top of each cylinder release the exhaust gases.
Daihatsu says its Storia minicar equipped with the engine can return over 70 mpg. Daihatsu also showed a 16 kilowatt methanol-powered fuel cell squeezed into a four-seat minicar. It could offer a glimpse into Toyota's highly secretive fuel-cell program.
Nissan Extroid transmission: Instead of belt-driven pulleys, this CVT uses rollers to pass engine torque between two discs with surfaces curved to resemble one half of an hourglass. The rollers are turned by pistons in the transmission to ride higher or lower on the curved disc face, changing the speed ratio between the driving half of the hourglass and the driven half.
The idea is not new; GM built a prototype more than 70 years ago. Nissan's transmission for rear-drive cars uses electronic controls and two separate sets of discs and rollers to return a 10 percent fuel economy gain over a conventional four-speed automatic, the company claims.