The world’s first variable compression ratio engine is here, in a production car. That car is the 2019 Infiniti QX50, debuting this week at the Los Angeles Auto Show. The midsize crossover has seen a refresh that has brought it an all-new platform together with new driver assist features, but it’s the engine that’s the centerpiece here.
Nearly everything is continuously variable under the hood of the QX50 – not only the new shift-by-wire XTRONIC CVT. The new VC-Turbo gasoline engine is able to change its compression ratio from 8:1 to 14:1, or anything in between depending of the driving situation; whether there is need for top-end power or turbodiesel-like torque from low revs, or optimized fuel economy. The pistons’ reach is continuously adjusted by an electric “Harmonic Drive” motor, which controls a multi-link system, affecting the top-dead-center of the pistons and changing the compression. The engine can also switch between efficiency-maximizing Atkinson cycle and regular combustion cycle, on the go – and there’s both multipoint injection and gasoline direct injection employed.
The result is 268 horsepower at 5,600 rpm and 280 pound-feet of torque at 4,400 rpm; good figures for a 2.0-liter four-cylinder gasoline engine with a single-scroll turbocharger. Infiniti says that the FWD version’s fuel economy of 27 miles per gallon combined is 35-percent better than the previous-generation V6 engine; in AWD guise, it reaches 26 mpg, which is a 30-percent improvement. The new engine is pretty much all-aluminum, but the vaguely magical-sounding “transformative multi-link components” behind the variable compression system are made from high-carbon steel alloy.
The engine’s multi-link system also enables it to do away with any balancing shafts, and Infiniti compares its smoothness to a V6 rather than a regular four-cylinder. In addition to the aforementioned tech, the VC-Turbo engine has the world’s first active engine mount vibration damping system to smoothen its operation even further.
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