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Nissan to unveil breakthrough variable compression engine at Paris show

POSTED BY Nigel Andretti ON 16 August 2016

Infiniti four-cylinder turbocharged gasoline VC-T engine

NISSAN subsidiary, Infiniti, will introduce a production-ready variable compression ratio engine VC-T (Variable Compression-Turbocharged) at the 2016 Paris Motor Show (Mondial de l’Automobile) in September.

Infiniti said that the new four-cylinder turbocharged gasoline VC-T engine has been in development for more than 20 years. (Nissan was awarded a patent in 1995 on compression ratio control for an engine.)

The 2.0-litre, four-cylinder VC-T engine averages 27 percent better fuel economy than the 3.5-litre V6 engine it replaces, with comparable power and torque. Nissan also says the new engine matches diesel engines for torque.

How Infiniti's engine featuring the Nissan multi-link VCR technology works: The piston and crankshaft are connected by means of the upper and lower links. The lower link is also connected, via the control link, to the center of the eccentric journal of the control shaft. Rotation of the crankshaft causes the lower link to revolve around the center of the main crankshaft journal and to pivot around the center of the crankpin. The motions of the lower link are constrained by the control link. As a result of the revolving and pivoting motions of the lower link, the connection point of the lower and upper links traces a vertically long oval shape as the piston undergoes reciprocal motion. When the compression ratio is varied, an actuator changes the angle of the control shaft relative to the engine, which moves the central position of the eccentric journal. Moving the center of the eccentric journal upward tilts the lower link clockwise, thereby shifting the top dead center (TDC) and bottom dead center (BDC) positions of the piston downward simultaneously to lower the compression ratio. Conversely, moving the center of the eccentric journal downward raises the compression ratio..

How Infiniti’s engine featuring the Nissan multi-link VCR technology works: The piston and crankshaft are connected by means of the upper and lower links. The lower link is also connected, via the control link, to the center of the eccentric journal of the control shaft.
Rotation of the crankshaft causes the lower link to revolve around the center of the main crankshaft journal and to pivot around the center of the crankpin. The motions of the lower link are constrained by the control link. As a result of the revolving and pivoting motions of the lower link, the connection point of the lower and upper links traces a vertically long oval shape as the piston undergoes reciprocal motion.
When the compression ratio is varied, an actuator changes the angle of the control shaft relative to the engine, which moves the central position of the eccentric journal. Moving the center of the eccentric journal upward tilts the lower link clockwise, thereby shifting the top dead center (TDC) and bottom dead center (BDC) positions of the piston downward simultaneously to lower the compression ratio. Conversely, moving the center of the eccentric journal downward raises the compression ratio..

Infiniti engineer Kinichi Tanuma, a senior Nissan engineer working for Infiniti, says the technology could replace diesel motors.

“We think the VC-T engine could replace or become an alternative to some of today’s advanced diesel engines,” he says.

“Diesel engine is a hot topic globally. We believe this new engine of ours is an ultimate gasoline engine that could over time replace the (advanced) diesel engine of today.”

Infiniti’s VC-T engine technology seamlessly raises or lowers the height the pistons reach. As a consequence, the displacement of the engine changes and the compression ratio can vary anywhere between 8:1 (for high performance, with the turbo) and 14:1 (for high efficiency). The engine control logic automatically applies the optimum ratio, depending on what the driving situation demands.

“VC-T technology is a step change for Infiniti. 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 2.0-liter turbo gasoline engine with a high level of efficiency at the same time,” said Roland Krueger, president of Infiniti Motor Company.

“VC-T technology delivers multiple customer benefits including significantly reduced fuel consumption and emissions, greatly reduced noise and vibration levels; it is also lighter and more compact than comparable conventional engines.”

Infiniti will present more information on the VC-T engine at Mondial de l’Automobile on September 29 during its press conference.