Internal Combustion Engine

The 2.5 liter variable compression engine uses the Atkinson cycle for its operation. Sometimes referred to as the five-stroke cycle, it uses a normal intake stroke but at the start of the compression stroke, the intake valve stays open. This allows a backflow stroke of air from the cylinder into the intake manifold which decreases manifold vacuum that requires energy to overcome. Although the intake valve stays open in the compression stroke, it closes early enough to produce sufficient cylinder pressure for combustion. The Atkinson cycle engine is designed to operate in a smaller RPM band than a conventional engine, and it runs mainly at the most efficient RPM range for the maximum fuel economy. The Atkinson cycle is up to 10% more efficient than a conventional four-stroke gasoline engine, but it has reduced low engine RPM torque. The engine is mechanically linked to the electronically controlled CVT by the crankshaft and transaxle input shaft. The engine primarily provides torque to the output shafts, charges the high voltage traction battery using the generator motor.