Infiniti Claims Variable-Compression Breakthrough

PARIS – Infiniti is set to unveil what it claims is the world’s first variable-compression-ratio engine at next month’s 2016 Paris auto show.

The premium sub-brand of Japanese automaker Nissan says its VC-T (Variable Compression-Turbocharged) 4-cyl. turbocharged gasoline motor is production-ready after more than 20 years in development.

“VC-T technology is a step change for Infiniti,” Infiniti President Roland Krueger says in a statement: “It is a revolutionary next step in optimizing the efficiency of the internal-combustion engine. This technological breakthrough delivers the power of a high-performance 2.0L turbo gasoline engine with a high level of efficiency at the same time.”

The technology overcomes the turbocharger’s weak point of not always running at peak boost because it is driven by exhaust-gas pressure. Compression ratios have to be set low to cope with the huge pressure loads at high revs while fuel and optimum power is wasted by not having a higher compression ratio at low engine speeds.

The automaker claims its VC-T engine technology seamlessly can raise or lower the height the pistons reach in their combustion chambers. In this way, the displacement of the engine changes and the compression ratio can vary between 8:1 and 14:1 depending on required performance or fuel efficiency. Its engine-management system automatically applies the optimum ratio, depending on demands made by the driver.

Infiniti claims the technology delivers significantly reduced fuel consumption and emissions, greatly reduced noise and vibration levels and also is lighter and more compact than comparable conventional engines.

German automaker Porsche was reported to have patented its own variable-compression-ratio engine early last year. Its system put the piston on an eccentric mount adjusted by control rods which swivel the piston up or down on the crankshaft connecting rod depending on oil pressure and so controlling the compression ratio.

Infiniti will present more information on its VC-T engine at a Sept. 29 news conference at the Paris show.