Subaru Legacy Review

You may have seen the advertisements for the Subaru Legacy Sports Tourer and Outback with the tag line, ‘It’s here’ - the world’s first boxer diesel-engined passenger car. But what is all the fuss about?

It’s all about symmetry, smoothness and economy but I’ll start with an explanation of the so-called ‘Boxer’ engine. It is also known as a horizontally opposed cylinder engine, which is a bit of a mouthful but provides something of a clue as to how it works. Whereas, in the more common layout, the pistons move up and down inside upright cylinders, in a boxer engine they are positioned sideways, working off a single crankshaft in between. The name ‘boxer, came about because of the action of each pair of pistons, moving simultaneously, mimic the punching actions of a boxer.

To see it in action is a thing of beauty as the sideways movement and synchronisation of the pistons is much smoother than in a more conventional engine and almost hypnotic. It also means that a balance shaft or counterweight on the crankshaft is not needed to counteract the weight of the reciprocating parts, making it lighter and less complicated.

So, this form of petrol engine is inherently smooth, efficient and relatively quiet but in developing the diesel version, Subaru has taken it a step further. Initially, the boxer diesel will only be used in cars bound for the European market and particularly the UK where 40 per cent of cars sold are diesels. So, it made sense to join in and gain a share in the market.

The result is a 2.0-litre, 4-cylinder unit, which is lightweight, compact and strong. Furthermore, the engine and transmission are mounted low, in a line and kept within the wheelbase for more efficient working, a low centre of gravity and better dynamics on the road.

In order to make the most of the new engine, there had to be a few modifications. For instance, the 5-speed manual gearbox has higher ratios to cope with the extra torque and lower engine speeds; the front springs have been tweaked to suit and the power steering is now electric, which helps to increase the fuel economy.

Long gone are the days when diesel-engined cars were slow, lumpy, for want of a better word, and just plain smelly. This common-rail, direct injection unit has a variable nozzle turbocharger, an inter cooler, a particulate filter, catalytic converters and exhaust gas re circulation, which allows it to meet Euro4 emission standards.