The engine in the TCH is a derivative of the Atkinson Cycle engine. Well - That's what Toyota calls it. What I think it really is - is either a modified Atkinson Cycle or a Miller Cycle engine minus the supercharger.

http://en.wikipedia.org/wiki/Atkinson_Cycle

http://modifiedatkinsoncycleengine.blogspot.com/

http://en.wikipedia.org/wiki/Miller_cycle

In the Modified Atkinson / Miller Cycle engine, the intake valve is held open during part of the compression stroke. At lower RPM, this release of part of the intake charge reduces the effective compression of the engine. At higher RPM or under boost, the volume of lost intake charge is reduced and the effective compression ratio is raised considerably.
The higher compression is only a detriment in the lower RPM band under high loading. In the upper RPM where the loading is lighter, the detonation (or early detonation) can be controlled via Knock Sensor, Timing and fuel calibration.

Doncha just love engines??? I do...

Regards - Randy




If there's one thing I've learned in online forums its this:
Never argue with an idiot, they'll drag you down to their level and beat you with experience!