STANFIELD, AZ – Shinichi Kiga cracks a smile as we lead-foot our Infiniti QX50 test mule down the back straightaway here at Nissan’s desert proving grounds.

Kiga, Nissan’s chief powertrain engineer-gasoline engine project group, has good reason to be pleased, considering what’s happening under the hood and how long he’s worked to bring it to fruition.

Running full bore, snapping off one aggressive redline shift after another, Infiniti’s 2.0L variable-compression turbocharged 4-cyl. – VC-Turbo, for short – is showing no signs of problems or strain, let alone catastrophic failure.

That’s remarkable given that, during operation, the engine is instantly and continuously varying the length of the stroke as much as 6 mm to change the compression ratio from 8:1 to 14:1, thereby achieving both remarkable power on demand and fuel efficiency in one tidy package.

The idea of the VC-Turbo isn’t new – Nissan had the idea as early as 1996 and engineers invented the Japanese automaker’s patented multilink device to make it work two years later. But until now no one has been able to put the concept into production.

All that changes in March when the ’19 QX50 premium midsize SUV rolls into U.S. dealerships powered by Kiga’s VC-Turbo engine, and the longtime powertrain engineer couldn’t be happier. Kiga has been immersed in development of the VC-Turbo in Yokohama for the past four years, joined two years ago by his U.S. counterpart, Christopher Day, senior manager-powertrain performance, who works here at the automaker’s Arizona Testing Center south of Phoenix.

In our test runs on both high-speed tracks and dynamic handling courses, the engine performs flawlessly, sending power to the wheels via a continuously variable transmission with D-Step Logic tuned to mimic an 8-speed automatic.

We observe the slightest hesitation in a wide-open throttle launch, but engine speed builds quickly to 2,000 rpm and then turbo boost kicks in to rocket the engine to its 6,000-rpm redline. Under full throttle, the engine holds near redline as it works through the gear ratios and speed builds past 100 mph (161 km/h).

At more modest speeds on the handling track, the engine provides ample power despite constantly varying speeds and throttle demands. We drive primarily in Sport mode, one of three options along with Eco and Standard that affect throttle response.

The engine sounds smooth and refined – almost V-6-like – with a distinct but understated exhaust note combined with pleasant throttle-matching blips on downshifts (in Sport mode). The engine recedes into the background while coasting and is barely audible at low speeds and while idling.

Anyone familiar with Infiniti’s power-packed V-6s, such as the 3.0L twin-turbo that earned a 2017 Wards 10 Best Engines accolade, will appreciate this engine’s capabilities and sophistication.