Japanese carmaker Subaru, known for its 4WD vehicles and the horizontally opposed Boxer engine family, has come out with a new Boxer diesel engine

Subaru has come up with the world's first Boxer diesel engine. A symmetrical AWD drivetrain layout, which mounts the horizontally opposed engine and transmission longitudinally, coupled with the AWD system, the Boxer diesel engine produces a powerful torque output of 350Nm at 1800rpm while complying with European EURO 4 regulations - it produces 148 g of CO2 per km.

Shown at the Geneva Motor Show the Boxer diesel would very soon power both, the Legacy and the Outback. Both the cars receive the diesel engine as part of the 2008 model line-up for the European market even as the Japanese carmaker is planning to make this engine one of the major driving forces within the European market. Expected to be made available in a wider range of vehicles in future models, the design of the horizontally-opposed engine is said to have a myriad of benefits. One of the most common is its compact design, which allows the center of gravity to be lower in the host vehicle. Additionally, since the boxer's pistons cancel out much of the vibration, the rotational balance is second to none.

Advantages like reduced vibration, low centre of gravity and high rigidity are said to be the main reasons mentioned by Satoshi Maeda, general manager of engine design department of Fuji Heavy Industries, for developing the Subaru Boxer Diesel engine. Maeda is also known to have expressed that there is yet another reason - the sporty feel. The bore pitch has been decreased and the left and right blocks holding the crankshaft provide a highly rigid design, which has also allowed use of an aluminium alloy cylinder block for weight saving. The result is the light weight diesel engine in the 2.0-litre class with an power output of 110 kW at 3600 rpm.

The movements of the horizontally-opposed pistons work in unison to effectively cancel out the second harmonic vibration, vibration with twice the frequencies as engine revolution, which human beings feel uncomfortable with. The layout results in minimal vibrations and rules out the need to employ a balancer shaft found in many conventional straight and V-type engine layouts. The crankshaft is short and highly rigid, minimising the vibrational noise characteristic of many ordinary diesel engines. The balance of the horizontally-opposed engine layout leads to low rotational inertia and friction within the engine itself. The result is exceptional accelerator response.

For Subaru, which sold 22 per cent less vehicles in 2007 than in 2006, the Boxer diesel will usher a welcome changes. It will also hike the appeal of Subaru vehicles bringing a larger audience under the brand focus.