Quote:
Originally Posted by merccom
not really, while variable valve timeing is useful one of the main aspects of the atkinson cycle engine is extremely high static compression which no amount of valve timing is going to change (the prius engine runs 13.5/1 static compression)
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I'm shaving a point pretty fine here, but I'm inclined to agree with Ecky. The central feature of the Atkinson cycle engine is the asymmetry of compression and expansion strokes. (The precise compression ratio number is less important in characterizing the cycle.) If the intake valve closes late enough to have significant blow back into the intake manifold (as described by Honda) then I think that qualifies as Atkinson cycle. In the Honda the effective compression ratio would be perhaps 8:1 while the expansion ratio would be 10.5:1.
Further supporting this interpretation is the fact that Honda says that manual throttle control would be effectively impossible, because the effect is so dramatic: the driver is applying very little throttle via the pedal, but the engine's throttle is near wide open. In most variable valve timing schemes manual throttle control is possible.
Finally, the Chevy Tahoe Hybrid engine
is described as Atkinson cycle, with a geometric compression ratio of only 10.8.