Subaru has developed a new Boxer engine that will start appearing in its cars from early next year, kciking off with the 2011 Forester
The new horizontally-opposed four-cylinder petrol engine will be available in 2.0 and 2.5 litre capacities, and reportedly improves fuel efficiency by 10%.
This third generation engine is the first major overhaul of the signature boxer powerplant in 21 years, replacing the motor that first appeared in the first Legacy in 1989.
Fuel efficiency comes by way of a more compact combustion chamber and a longer piston stroke.
Tumble generated valves in the intake ports and an exhaust gas recirculation cooler also aid efficiency.
Subaru has also included an active valve control system on both intake and exhaust valves, allowing valve timing to be advanced or delayed for maximum engine performance in output, fuel efficiency, and exhaust emission.
The use of lightweight moving parts, such as pistons and connecting rods, and an efficient and compact oil pump, provides about a 30% reduction in friction loss.