I have read GM is using the Atkinson cycle on the LE5 2.4 ecotec by holding the intake valve open during part of the compression stroke they are reducing part throttle fuel consumption. Also they are opening the throttle fully at the same time to reduce pumping losses (Quite ingenious) the result is effectively a lean burn cruise at WOT. My 2.2 ecotec is not VVT so no Atkinson cycle