QUOTE:- I have to say that I was exceptionally disappointed when I learned that the Atkinson-Cycle engines used by both Toyota and Ford (Escape Hybrid) were not true Atkinson-Cycle in that they still have 4 distinct cycles and it takes two full revolutions of the crankshaft to complete one power cycle.
The True Atkinson Cycle engine takes 1 full revolution to accomplish all 4 strokes via it's linkage and intermediate shaft (a marvelous design).

The Engines we are dealing with here are (for all intents and purposes) standard Otto Cycle 4 stroke engines that have a special valve timing mechanism (VVT). I truly have no idea at this point how either Toyota or Ford can claim Atkinson-Cycle engine..


Probably the "modified" Atkinson-Cycle (I think this is what I've heard this design called), engine that Toyota produce has the advantage of simplicity and less moving parts to wear out.

I assume it would be possible to boost the output of the engine by closing the intake valves sooner thus upping the effective compression ratio on the combustion stroke to the maximum that premium fuel could tolerate? I'm not suggesting anyone try this it's just a hypothetical question.