PHOENIX -- When the next-generation Infiniti QX50 crossover arrives next year it will be powered by a 2.0-liter turbocharged four-cylinder engine introducing a technology never seen before in a regular production vehicle: variable compression.
Under development at Nissan for 20 years, the Variable Compression – Turbo -- VC-T engine -- has a device that changes the distance the pistons travel in their cylinders by as much as 6 mm, or about a quarter of an inch.
It's an idea that automakers, such as Saab, and engine developers, including AVL, have tried to perfect over the years. The reason: Varying the compression ratio has the potential to offer dramatic improvements in power and efficiency.
Shinichi Kiga, Nissan's chief powertrain engineer, says Infiniti's VC-T engine is expected to deliver a combined city-highway U.S. EPA-rated fuel economy gain of 27 percent over the QX50s's outgoing 3.7-liter V-6. The VC-T engine is rated at 268 hp and 288 pound-feet of torque. Kiga says the 2019 QX50 will reach 97kph (60mph) almost one second faster than its four-cylinder competitors.
Infiniti last week allowed a few reporters to drive early pilot-build 2019 QX50s at the company's test trackhere. The VC-T's power and refinement were impressive. The technology works in such a manner to make it invisible to the driver. There are no buttons to press, no switches to turn and no strange noises, vibrations or sounds -- just smooth, abundant power and a pleasing, performance-tinged growl from under the hood.
How it works
The pistons in all of today's automotive internal combustion engines travel the same distance up and down in the cylinder, regardless of speed and vehicle load. The pistons are connected to rods that are mounted to the crankshaft. The engine's compression ratio is fixed and is determined by the amount of space above the pistons when they are at the top of their travel. The smaller the space above the pistons, the higher the compression ratio and the greater the engine's power output.