309
The BMW 309 was a development of the 303. A replacement for the 3/20, the 309 was a 303 with a four-cylinder engine developed from the M78 six-cylinder engine used in the 303. The 309's engine had the bore increased from 56 mm to 58 mm which, with a stroke of 80 mm, gave a capacity of 845 cc and maximum power of 16.5 kW at 4000 rpm.
In addition to the body styles offered with the 303, the 309 was also available as a tourer.
With the same body as the 303, the 309 offered the same amount of room at a lower cost and a lower tax rating based on its smaller engine. The 309 was manufactured from 1934 to 1936, with a total of 6,000 made.
Six-cylinder successors: 315, 319, and 329
The 315 replaced the 303 in 1934. The 315 differed from the 303 mainly with its larger engine, with increases in both the bore, to 58 mm from 56 mm, and the stroke, to 94 mm from 80 mm.
The 319 were introduced in 1935. Produced alongside the 315, the 319 differed from it mainly by its new, larger engine with a bore of 65 mm, and a stroke of 96 mm, resulting in a displacement of 1911 cc. This resulted in an increase in power to 34 kW at 3750 rpm. The kerb weight of the 319 was 850 kg, and the fuel capacity was 40 L.
Upon the introduction of the BMW 326 in 1936, the 315 and 319 were no longer BMW's largest cars.
The 315 and 319 were discontinued in 1937. A total of 9,765 BMW 315s were built, including two-door saloon cars, touring cars, convertibles, sport convertibles, and 315/1 roadsters. A total of 6,646 BMW 319s of all types were built by the end of production in 1937.
The 329 replaced the 319 in early 1937. The 329 was basically a 319 with the front bodywork and fenders from the BMW 326. The 329 was available only as a convertible, with either two or four doors. The 329 was replaced by the 326-based BMW 320 later in 1937.
315/1 and 319/1 roadsters
The BMW 315/1 was a sports car based on the 315 saloon. It used the same chassis as the 315 saloon and had an engine of the same displacement. However, with compression ratio increased to 6.8:1 from 5.6:1 in the saloon, and with the use of three Solex carburetors, power increased to 30 kW at 4300 rpm, while the roadster bodywork reduced kerb weight to 750 kg.
The BMW 319/1 was a 1.9-litre version of the 315/1 introduced alongside the 319 in 1935. The dimensions of the 319's engine with the performance modification of the 315/1's engine resulted in 41 kW at 4000 rpm in the 319/1 roadster.
Production of the 315/1 and 319/1 roadsters ended in 1936, with 242 of the 315/1 roadsters and 102 of the 319/1s built. The 315/1 and 319/1 were replaced by the BMW 328, which was based on an all-new tubular steel ladder frame, but used the steering gear and suspension of the 319/1.
