The telephone commutation to improving fuel efficiency lies inwards raising an engine’s thermal efficiency. This tin endure done past times increasing the expansion ratio. The expansion ratio is the sum of operate the engine does each fourth dimension the air-fuel mixture inwards the cylinders detonates. However, inwards conventional engines the expansion ratio is the same every bit the compression ratio, too thence increasing the expansion ratio volition besides heighten the compression ratio. This is a work because a high compression ratio causes abnormal combustion, or knocking.
The answer is the Miller-cycle engine. By delaying the closure of the intake valves, compression truly begins business office means through the compression stroke, which results inwards a reduced compression ratio. At the same time, changing the cast of the piston crown decreases the combustion bedroom minimum volume, resulting inwards a larger expansion ratio. In this means nosotros tin decrease the compression ratio too field increasing the expansion ratio. In other words, the Miller-cycle engine has a higher expansion ratio than compression ratio.
Mazda’s naturally-aspirated MZR 1.3L Miller-cycle engine delays the closure of the intake valves to amend the thermal efficiency (high expansion ratio). Sequential-valve timing (S-VT) is besides employed to optimize intake valve timing too ensure sufficient torque for cruising too accelerating. Furthermore, the engine is mated to a continuously variable transmission (CVT) for a perfect blend of responsive acceleration, shine gear shifts too top-class fuel economy.