Mazda's commercialization of the Miller-cycle engine, an invention dating back to the 1940s, got more Japanese media attention than any single advance in fuel conservation. The engine generates 1.5 times the torque of a traditional engine of the same displacement, while improving fuel efficiency 10 to 15%. In the Miller cycle, the compression stroke is shortened to attain a small compression ratio with a large expansion ratio. The engine achieves both low compression ratios and high expansion ratios by delaying the close-timing of the intake valves. To compensate for the decreased amount of intake air, caused by the delay of the closing intake valves, a Lysholm compressor pushes a large volume of compressed air into the cylinder with a screw-type rotor mechanism. Mazda's KJ-ZEM Miller-cycle engine is a 24-valve V6 DOHC model with a bore of 80.3 mm, stroke of 74.2 mm, displacement of 2,254 cc, actual compression ratio of 8.0, maximum torque of 30.0 kg-m/3,500 rpm, power output of 220 ps/5,500 rpm, and high expansion ratio of 10. The Lysholm compressor sits in the V-bank between the cylinder blocks and is driven by a V-belt. Rotors take air in and compress it by a factor of two. A 1.5 X increase in air volume goes to the combustion chamber even if a portion returns to the inlet manifold because of the delayed closing of the inlet valves.
Mazda employed a hydrogen rotary engine on its HR-X2 concept vehicle that contains several improvements compared to commercially available versions. Most interesting is the improved torque in the low-to-mid rpm range. Mazda changed the point of hydrogen injection from the side of the rotor housing to the top of the housing. This shortens the distance between the hydrogen-intake valve and the rotor housing. During intake, hydrogen enters the chamber from a different port than air.
The HR-X2 is an updated version of the hydrogen powered HR-X introduced at the last Tokyo show two years ago. Besides the improved rotary engine, the HR-X2 boasts of a cell-type metal-hydride fuel tank. To store large quantities of hydrogen, it takes advantage of the fact that hydrogen passes easily between the relatively widely spaced atoms of metals. Metal hydride absorbs hydrogen when cooled, and releases it when heated. To release hydrogen, warm water is drawn into the tank to provide a heat source. Even if the tank is unintentionally broken, the release of hydrogen naturally cools the metal hydride to prevent any further loss.
The vehicle is also billed as 100% recyclable. Mazda designed the car based on the possible use of liquid-crystal polymer fiber reinforced plastic, which is said to retain strength after recycling, thus allowing it to be used repeatedly. (The version on display, however, was not actually built with this advanced plastic.) Vehicle structure promotes easy detachment of the upper body from the metal under the chassis. Door panel openings have been enlarged to make it easier to remove functional parts such as the regulator and motor. Seat cushions are the press-and-fit type for easy detachment. For the sake of easy disassembly, headlights mount directly under the windshield, and meters and switches in the instrument panel are integrated with the headlights and turn signals.
The EVX is an electric vehicle designed by Honda. It uses a recyclable lead acid battery and solar panels covering the roof. Electricity to be used by headlights, audio, and ventilation systems comes from an auxiliary battery. To reduce electricity use, headlights have discharge tubes and rear lamps are LEDs. Mileage between charges is said to be 150 km, at maximum speeds of 130 km/h. Nissan AP-X
The four-door AP-X is a concept car designed to show Nissan's philosophy for future sedans. It uses infra-red scanners to detect pedestrians or animals on the road at night, flashing an instrument-panel warning if anything shows up. Radar cuts through rain or fog to measure distances to preceding or following vehicles. The car bleeps a warning if the gap narrows too much.
Honda's Future Safety Research vehicle automatically reduces speed for sharp corners and uses bumper-mounted cameras to transmit images to a dashboard display. The tiny front cameras are positioned so the driver can see around corners in urban traffic. Honda did not explain why cameras are better than nose-mounted mirrors, however. Critics call this a perfect example of how car makers are preoccupied with exhibiting technological prowess but unsure how to benefit drivers or themselves with it.
Other features on the vehicle include a rear message board to transmit driver intentions to other cars, a strobe light in the door pillar to make an open door more visible to vehicles approaching from the rear, and a specially designed hood to reduce front impact loads.