Is Nissan's VCR just marketing for Atkinson?
 

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/

Re: Is Nissan's VCR just marketing for Atkinson?
 

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

Re: Is Nissan's VCR just marketing for Atkinson?
 

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.