Quote:
Originally Posted by Ken Fry
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. |
Ok I will concede that yall are correct. I will say that the situation is not optimum however. If you have an engine that has 10/1 static compression when the cams retard and you go atkinson your dynamic compression could be in the 7/1 range which certainly would be no good for fuel mileage.
Another line of thought I've been going down is maybe ruNning standard otto cycle but at 12 or 13 compression and using water injection to control detination under load while keeping the advantages of increased compression under part throttle.
Just want to reiterate that of course vehicle optimazation comes first. But after that is done what can be done to build a better engine