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Why select the horizontally opposed engine? (2)

Friday, 3 Aug 2012

Based on the required conditions for passenger vehicles that were presented by Shinroku Momose, the engine design department proposed three engine types, namely the transversely mounted in-line four-cylinder engine, the longitudinally mounted V-type four-cylinder engine, and the transversely mounted horizontally opposed four-cylinder engine.

“It was because the drive shafts could be equal length and also made longer. In FWD development at that time, the greatest problem was the drive shaft joints. Excellent joints were subsequently completed just before launch of the Subaru 1000, however, in order to avoid placing load on the joints, it was necessary to extend the drive shafts and make them equal length. However, this was difficult to achieve with the transversely mounted in-line four-cylinder engine.”

Development of the horizontally opposed engine was thus commenced, and the first engine to be designed was an 800 cc 36 HP engine, and based on this a 796 cc, 41 HP prototype was manufactured. This was subsequently upsized to a 923 cc, 46 HP model then a 977 cc, 47 HP model, and finally the EA-52 Engine 977 cc, 55 HP model was developed for mass production.

Aluminum was adopted as the material for the crank case and cylinder head in order to reduce weight. At that time, aluminum was 14 times more expensive than iron; moreover, because this wasn’t a typical in-line four-cylinder engine, all machine tools had to be specially ordered. Every time something cropped up, there was a discussion over whether the horizontally opposed four-cylinder engine was really the best choice. Even so, the engine development team built an aluminum horizontally opposed engine based on the steadfast belief that “a good product will always sell.”

As a result, the EA52 engine turned out to be 15 percent lighter than conventional in-line four-cylinder engines. At that time, in development of common mass production vehicles, engine and car body performance was pursued, but this was the first time that an effort to improve driving was made through reducing the engine weight. This was very unusual, but this most important weight reduction was thoroughly conducted in the Subaru 1000.

(The above contents were edited using extracts from Cartopia Vol. 314 and Vol. 382).