I have noticed several articles in recent car magazines referencing Nissan's VCR (variable compression ratio) engines. The VCR engines are planned with turbos to compensate for the lack of low-end torque. On the surface the technology sounds a lot like the Atkinson cycle used in most hybrid systems. Also, an Atkinson engine with supercharger is referred to as a Miller cycle engine (Mazda Millenia). Would a turbo Atkinson be referred to as a Miller cycle?

FWIW, seen several other articles reference other manufacturers utilizing "variable compression ratio" engines, without the "VCR" acronym. It is unclear if VCR is a trademarked Nissan logo or soon to be synonymous with Atkinson (or pseudo-Atkinson) like VTEC is with variable valve timing.

http://www.nissan-global.com/EN/TECH...N/DETAILS/VCR/

 

Yes. What I don't know is if an Atkinson, high expansion system could be combined with a compression ignition system. What this would do is further reduce the exhaust gas temperature and improve thermodynamic efficiency. There would be an increase in engine weight.

Bob Wilson

 

Although this VCR design has some of the characteristics and advantages of the Atkinson cycle, I think it deserves it's own name because it is using a modification of piston motion rather than a modification of the valve timing. In fact, it appears one could combine some degree of Atkinson valve timing adjustment with this engine and perhaps get even greater benefits in a hybrid. It's a really interesting concept.