TOKYO -- Subaru said its next-generation, horizontally opposed engine will debut this year in the Forester and deliver a 10 percent improvement in fuel economy.
The four-cylinder engine, which will come in displacements of either 2.0 or 2.5 liters, is the first major overhaul of the brand's signature boxer power plant in 21 years, Subaru's Japanese parent company Fuji Heavy Industries Ltd. said.
Engineers bettered fuel efficiency 10 percent over the current generation of boxers, which were introduced in 1989, by tightening the bore of cylinders and stretching out the piston stroke.
They also changed the intake port configuration and introduced an active valve control system to deliver more precise control over intake and exhaust valve timing.
Adding to the performance are lighter pistons and connecting rods, and a more compact oil pump. Those help generate a 30 percent reduction in engine friction loss, Subaru said.
The new engine will be positioned as Subaru's main engine and be deployed in other models besides the Forester, the company said.
The four-cylinder unit will be built at the Subaru's new Oizumi plant in Gunma prefecture northwest of Tokyo. The factory was finished in January and began building the engine in July.
Subaru needs more-efficient drivetrain technologies to help it meet tougher fuel economy and emissions rules being introduced in Europe and the United States.
It has already said it will add a hybrid powertrain to an existing model in 2012. And it may introduce continuously variable transmissions throughout its lineup to boost fuel efficiency after inaugurating the technology in last year's redesigned Legacy.