Subaru’s box of tricks: the boxer engine explained
- 1st September 2020, 9:00am
Incidentally, that first boxer engine from Subaru was rated at 977cc and developed a mere 55bhp, a far cry from today’s sophisticated, powerful engines.One of the beauties of a boxer engine is its balance. Because it’s a symmetrical layout with a north-south crankshaft, the driveline is able to extend from the front of the engine right through to the rear wheels. In addition, the weight distribution either side of that straight line is symmetrical, a feature that enables the engine to benefit from this balance effect. Over the past 65 years, Subaru have had numerous opportunities to change to a more conventional engine layout design, but have stuck with the boxer all this time. One of the principal reasons is the engine’s balance and light weight. It’s also compact, is mechanically simple, strong and rigid. If you look at a Subaru engine you’ll notice that the crankshaft webs are very thin because the flat-four is so well balanced. Compare a Subaru engine to a conventional in-line crankshaft and you’ll notice the large cast-iron balancing webs found on other engines. The flat-four engine benefits from better volumetric efficiency. There’s equal-length intake manifolds and a crossflow cylinder head design which helps the engine’s breathing. An incidental but important feature of the design is that it allows the engine to sit low in the engine bay, offering optimum handling, as opposed to other sorts of engines which sit very high in the chassis. Chassis balance is also a plus-point as the engine doesn’t overhang the front axle. It’s strong, too. Subaru engines commonly go for 200,000 kilometres or more without being touched, thanks to the initial design. Structurally, the boxer engine has a rigid cylinder block where the crankshaft is sandwiched between the left and right crankcases with their own cylinder head on each bank. As far as the cylinder heads are concerned, there are four valves per cylinder in a crossflow format, inclined at 30 degrees. This helps to keep the combustion chambers a compact size; there is also a single camshaft and roller rockers. Turbocharged or non-turbocharged, Subaru’s now-familiar boxer engine has developed an enviable record right around the world for power, reliability and strength. On top of that, there’s that distinctive boxer beat from the exhaust that never fails to send a shiver of excitement down the spine. For road use or competition, Subaru’s famous engine looks like punching on for a long time to come. https://www.youtube.com/watch?v=8BWEcXe6NU0&feature=emb_logo https://www.youtube.com/watch?v=0qD_orR3uNM
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