Infiniti's next-generation compact crossover, previewed by the QX Sport Inspiration concept revealed at Beijing earlier this year, will likely be the first production vehicle to use variable compression ratio technology in an engine that will promise V6 power with diesel fuel economy.
We've heard promises of powerful-yet-efficient engines before from every manufacturer that has jumped on the turbocharging bandwagon in the last half-dozen years, but this news, which comes to us from the U.K.'s Autocar magazine, suggests this technology could be a real game-changer if it comes to fruition.
This is all pure speculation, and Autocar doesn't get into much detail about the variable compression ratio engine tech, but we did find a page at Nissan's global website (that was later removed) that describes it quite well. Essentially, VCR (for variable compression ratio) takes the kind of engineering that allows for variable valve timing and applies it to the crankshaft, which converts the back-and-forth motion of an engine's pistons into the rotational torque needed to make a car go.
Specifically, Nissan's system adds a link to the connecting rod which allows the rod to be bent slightly to decrease the compression ratio and extend to increase it.
Nissan's description says the system would enable high-compression operation in city driving, "to increase thermal efficiency," a fancy way of saying more of the energy created by the burning of fuel gets turned into power instead of heat. In simpler terms, this is the kind of thing that makes diesel engines more fuel efficient than gas burners.
In situations requiring more power, like quick acceleration or climbing hills, the engine would switch to a lower compression ratio and engage a turbocharger to pump a denser mixture of gasoline and air into the engine in order to boost output.
Mazda's modern "SkyActiv" engines have shown us that a high compression ratio in a gasoline-fuelled motor can generate good torque and fuel economy, even if those engines' performance isn't exactly revolutionary. But if Infiniti does bring VCR to a new production model by late next year or early 2018, as Autocar suggests might happen, it would likely be the first to market with a variable compression ratio engine.
Infiniti has two aging five-seat crossovers -- QX50 and QX70 -- in its lineup right now, and we don't know whether this new design would replace one or both of them, but along with the QX30 set to go on sale later this year, it will do much to freshen the brand's crossover lineup.
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