Subaru is sticking to its almost trademark horizontally opposed or ‘boxer’ engine for its future lineup of cars, improving on the design, making it more refined and fuel efficient with each generation. The third and latest generation of the engine--the first major redesign in 21 years--has now been revealed and is scheduled to debut in the 2011 Forester towards the end of the year before filtering across to other models in the automaker’s lineup.

The engine is almost entirely new, starting from the basic structure, yet it maintains all the advantages of the horizontally-opposed layout: lightweight, compact, low center of gravity, and superior vibration balance.

Peak output stands at 146 horsepower and 145 pound-feet of torque.

The key difference between the new engine and previous designs is the environmental factor; it is roughly 10 percent more fuel efficient than the four-cylinder unit it replaces in Subaru’s lineup. Improved fuel efficiency has been achieved through optimization of intake port configuration and the addition of partitions inside ports, the use of TGV (Tumble Generated Valve), and the use of an EGR (Exhaust Gas Recirculation) cooler. Furthermore, Subaru has designed the new engine with consideration of the technology’s expandability and potential capability to receive further upgrades meeting future environmental measures.

The engine displaces either 2.0- or 2.5-liters and can be matched with either a manual or continuously variable transmission. Production will take place at Subaru’s new Gunma Oizumi plant in Japan.