Infiniti has revealed the world’s first, production-ready variable compression ratio engine, which will make its public debut at the 2016 Paris Motor Show. The new VC-T (Variable Compression-Turbocharged) unit is a 2.0 litre four-cylinder petrol engine, which is expected to go on sale in 2018, making Infiniti the first carmaker in the world to sell an engine with the technology.

Infiniti’s VC-T technology allows the engine to raise or lower the height the pistons reach, allowing for the engine’s displacement of the engine to change, and the compression ratio to vary seamlessly between 8:1 (for high performance) and 14:1 (for high efficiency).

This is accomplished through a mechanical actuator arm that is connected to the piston’s conrods through a slot in the side of the engine block, which controlled via the engine’s control logic that determines the optimum ratio to be applied depending on the driving demands.

The actuator arm is operated by an electric motor fitted on the outside of the engine block, and pushes a lever-type link that joins the conrods, which themselves are made in two halves. This effectively changes the length of the conrods, where a higher compression ratio is achieved with a longer length, and vice versa.

Infiniti VC-T tech diagram

Furthermore, the engine has two parallel fuel injection systems, one direct and one into the intake manifold, and can switch between the standard combustion and fuel-saving Atkinson combustion cycles. The engine has been in development for more than 20 years, since 1998, and can benefit from hybridisation for an estimated further 10% improvement in fuel economy.

The all-new engine serves as a replacement for Infiniti’s 3.5 litre V6, and is expected to be used on the new QX50, followed by the Q30 and QX30 in the future.

In terms of power, the VC-T unit develops around 270 hp and 390 Nm of torque, and is claimed to be 27% more economical than an equivalent petrol engine without variable compression ratio technology. The Autocar report also says that the engine’s NVH levels are similar to a petrol V6, and is cheaper to build than a Euro 6-compatible diesel engine.