Quick Spin : Subaru New Engine Helps Smooth Out Most Rough Edges

In the years since Subaru last gave its workhorse flat four-cylinder engine a significant revision, an entire generation of customers has gone from pulling up their Huggies to donning college graduation gowns. More than two full decades have passed since the company's engineers seriously sat down to re-examine the engine's architecture, and in that time, there's been an explosion of automotive technology geared toward squeezing every last bit of energy out of a drop of gasoline. With fuel economy and emissions standards growing tighter by the day, the minds at Fuji Heavy Industries, Subaru's parent company, unveiled the third-generation of their boxer engine recently.

But at first blush, the new heir to the Pleiades throne looks to be little more than a carbon copy of its predecessor. Horsepower, torque and fuel economy figures are all within a shave of the old engine's numbers, and while the company's competitors are investing heavily in direct-injection systems, Subaru passed on this tech all together. Where was the improvement? Judging by the specs alone, we had to wonder why Subaru went through the trouble of building an entirely new facility just to produce what looked to be the same old beating heart we'd known and loved for years. We jumped behind the wheel of the 2011 Subaru Forester to find out just what had changed beneath the hood of its all-wheel-drive family hauler

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2011 Subaru debuts third-generation boxer four-cylinder engine

Fuji Heavy Industries, parent company of Subaru, has introduced the latest, third-generation boxer engine that will relieve the second-gen after 21 years of service. This is a brand new lump, not a rework, and FHI has built a factory just to produce it.

The New-generation Subaru Boxer engine

• The bore and stroke, the basic structure of this engine, have been reviewed to achieve a compact combustion chamber as well as a long stroke, which was difficult previously due to chassis mounting conditions in boxer gasoline engines. This allows high combustion efficiency, and generates a sufficient mid-low speed torque with improved fuel efficiency and practicality.
• 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.
• AVCS (Active Valve Control System) is used on both intake and exhaust valves. For the intake side in particular, an intermediate lock system allows valve timing to be advanced or delayed for precise control over intake and exhaust valve timing, allowing maximum engine performance in output, fuel efficiency, and exhaust emission.
• The use of lightweight primary moving parts, such as pistons and connecting rods, and a highly efficient and compact oil pump provides an approximately 30% reduction in friction loss and improves fuel efficiency and revolution response.
• Cooling has been optimized by using separate engine cooling circuitry for the block and the head, resulting in improvements in fuel efficiency and output characteristics.

FHI is fully committed to develop new products on the theme of integrating enjoyable and reliable driving with environmentally friendly solutions. This same theme applies to this new-generation boxer engine, which will be
positioned as a main engine and the starting point of its future power unit strategy. Starting with the 2011 Subaru Forester, the new engine will be deployed in other Subaru products in the future.

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