Infiniti Touts Low-Cost Alternative to Diesels

Nissan Motor Co.’s Infiniti arm says turbocharged 4-cylinder gasoline engines outfitted with its new variable compression technology can equal the fuel efficiency of a diesel engine at a much lower cost.

The carmaker will launch the technology next year with a turbocharged 2.0-liter engine in the 2018 QX50 crossover/SUV. The VC-T (variable compression-turbo) engine is expected to be 27% more fuel efficient than the naturally aspirated 3.5-liter V-6 it replaces, while generating comparable power and torque (268 hp and 248 lb-ft) levels. Other benefits include improved noise and vibration characteristics and reduced weight.

Tailpipe emissions also promise to be “significantly” lower and won’t require the expensive aftertreatment systems of diesels. Describing the system as the “ultimate gasoline engine,” Infiniti product development chief Kinichi Tanuma says variable compression engines could eventually replace small diesel mills.

By adjusting piston height within the cylinder based on real-time driving inputs, VC-T can vary an engine’s compression ratio between 8:1 (for high performance) and 14:1 (for high efficiency). This eliminates the typical tradeoffs made with conventional piston setups that maintain a constant compression ratio. The VC-T’s low-end capability also enables higher turbo boost pressure without engine knock or the risk of detonation.

Nissan says it has more than 300 patents and pending patents related to the technology, which has been in development for about 20 years. The technology can be scaled to other sizes of 4-cylinder engines but isn’t practical for V-6 or V-8 engines, according to the carmaker.