Hi I'd like to know what some good cars are that have the Atkins-cycle modified Otto engine as well as a few questions about this engine. I'm amazed at the cleverness of simply changing the timing of the intake valve to change a regular gasoline engine (otto cycle) into a atkins cycle engine. It seems like a very minor change, and I'm wondering why this wasn't popularized decades and decades earlier. I believe Toyota was the first to mass market this technology, in their Prius hybrid cars. First, a brief three sentence review just for those who haven't wiki'ed modern Atkins-cycle modified gasoline engines: the idea is that far greater efficiencies can be achieved if you allow some intake air to backwash out of the cylinder back into the manifold early in the compression stroke, by leaving intake valves open just a bit longer at the very beginning of the compression stroke (right after the intake stroke). The effect is, that with less air taken in, the expansion/power stroke becomes longer than the effective intake stroke, and you get a lower pressure at the point where the power stroke is finished and the exhaust valves open--meaning that the waste energy at the end of the cycle is reduced. The method of reducing intake air (and corresponding fuel) with this valve timing method is much superior to the ubiquitous throttling off the intake air with the throttle plate, which was the method for about a century of automobile engines. In typical city driving, the engine spends so much time in minimal engine efficiency conditions where the throttle plate is choking the engine off air to near the point where the engine is doing zero net work (just overcoming friction to keep spinning). (Direct injection has improved idle condition consumption greatly, but my regular injection ~2l four-cylinder consumes almost a third a gallon per hour at 800 rpm idle--in driving conditions where I'm following traffic at constant speed with standby power, say at 2400 rpm, that's ~1 gallon per hour for producing no work! You're basically running somewhat of a vacuum pump not an angine; my manifold pressure is at about a third an atmosphere in idle conditions.) So, given this, why didn't this modification arrive decades earlier?? I hear one argument is that the horsepower is reduced, since less intake air+fuel per cycle is burned. However, wouldn't it be possible to make the engine be capable of switching on and off between otto and atkins cycle? It would seem you could use some type of adjustable cam to pick what ratio of ottoishness or atkinsishness are appropriate for the conditions, or alternatively, just some clutch system in the cams that would switch on and off between otto and atkins intake valve timing. Is this technology dependent on direct injection technology, or does it work well enough with standard fuel injection; i.e., is it a problem if you let fuel-air mix backwash rather than just air. For all model cars that I've browsed, the engine only seems to be available in hybrid models. Are there any non hybrid cars (or at least hybrid-lite) that use the Atkins cycle? Finally, what are your recc's for medium sized, or larger compact, models. The ford fusion seems pretty decent, as well as various toyotas, but I'm wondering what other brands are out there.