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beautifullyengineered:

BMW S14 - DTM Version

Excerpts regarding this engine from the article “25 years ago a champion in touring car racing, the E30 M3 was born.” Full article is here.

“…Four cylinders meant less weight and high torque, an ideal platform for a sports engine in the projected displacement class. Naturally enough, the series four-cylinder engine was much too tame for a sports engine. A comprehensive power boost was called for in order to turn the plucky daily workhorse into an athletic and sporty power unit. The BMW design engineers increased the displacement to 2.3 liters and applied a formulation that had already achieved significant successes over a period of many years: four-valve engineering. There was also another reason for the decision to opt for a four-cylinder engine and not adopt the six-cylinder engine introduced in the BMW 3 Series. The longer crankshaft in the big engine started to vibrate much earlier than the shorter four-cylinder shaft. The design engineers therefore designed the crankshaft drive of the BMW M3 with sufficient torsional stability to achieve 10,000 revolutions a minute and more. By comparison with the four-cylinder engine installed in the series vehicles, this represented an increase of more than 60 percent.

Paul Rosche recalls: “We started work immediately. One advantage was that the big six-cylinder engine originally had the same cylinder gap as the four-cylinder engine. We therefore cut two combustion chambers off the four-cylinder head of the M88 and bolted a panel over the hole on the rear side.” This meant that the new four-cylinder engine had a second forebear. The six-cylinder engine that had initially created a sensation in the M1 and had meanwhile transformed the M635CSi into one of the fastest coupés in the world. Paul Rosche: “Whether you believe it or not – we had created an outstanding four-cylinder engine for the 3 Series within the space of two weeks. Under the development name S14, this engine was to generate headlines in sport and in volume production over the years to come….

…A World Touring Car Championship was held for the first time in 1987. And that was exactly what the M3 had been built for. But not quite in the guise in which it was seen on the streets. Instead of 200 hp, the 2.3 litre engine delivered up to 300 hp at 8,200 rpm in the racing version. This put it on a par with the BMW M635CSi….”