For the new roadster model to fully exploit the popular two-litre class, the 319 engine originally designed by Rudolf Schleicher was bored out by a millimetre to give a displacement capacity of 1971 cc. Furthermore, hemispherical combustion chambers and sticking valves arranged in V-position were essential for enhancing performance in a high-powered engine. This led to the construction of a new aluminium cylinder head with vertical inlet ports for triple Solex downdraught carburettors.

Financial constraints, however, meant that the far from ideal valve operation using a camshaft positioned underneath had to be retained. Developing the sophisticated new cylinder head had already taken a huge bite out of the tight budget. In an attempt nevertheless to preserve the advantages of an overhead-type engine, a rather unorthodox solution was found, one considered by some experts as entirely unworkable. With the help of intermediate transverse pushrods, the exhaust valves were also controlled via the rocker shaft of the intake valves. Visually the result was more or less indistinguishable from a DOHC power unit, which led to some confusion in the motoring press.

Though not entirely new, this technical solution sparked off controversial discussion. But the BMW constructors were ultimately vindicated by the engine's success. This power unit, which freely delivered 80 bhp, allied to the lightweight chassis developed by Fritz Fielder and the 328's almost graceful, open bodywork proved a virtually unbeatable combination. The BMstylists had indeed wrought an extraordinary achievement with their bodywork design for the new roadster model. At first sight the 328 displayed a clear kinship with its 319/1 forerunner: the low-slung basic design with its flowing wings seemed to have been retained. On closer inspection, however, the 328 revealed a completely new body. The bonnet was considerably longer and hinted at the power contained in the six-cylinder beneath, while the car as a whole had a much more stretched and also more pounded profile. One highly fashionable feature were its headlamps, which were sunk into the cowling and, together with the covered rear wheels, reflected the design's enhanced aerodynamics. The cockpit, tailored around the driver and co-driver and bristling with switches and attractive instruments, exuded elegance and racing flair at the same time. No frills or frippery distracted from the essential purpose of the BMW 328: functionality reigned supreme.

Even as a prototype the BMW 328 Roadster was to gain its first important victory. Ernst Henne, the famous motorcycle world record holder, drove the new BMW home to a supreme win at the Eifelrennen at the Nurburgring on 14 June 1936. Almost two-and-a-half minutes elapsed before the runner-up, a turbocharged Alfa Romeo, crossed the finishing line. Private buyers had to wait until spring of 1937 before taking delivery of the first batch of BMW 328's. Priced at 7,400 reichsmarks, the BMW 328 was not exactly a bargain basement offer: one of Opel's popular six-cylinder saloons could be had for less than half that sum, and even the BMW 326 saloon came almost 2,000 reichsmarks cheaper. But with a top speed of just over 150 km/h (93 mph) and lively acceleration, the BMW 328 ranked among the truly fast cars in the land and soon came to be the dream car of the seriously sporty motorist. But you could just as easily snuggle into the 328 Roadster and take a spin around the countryside, or indeed go on holiday with it: it had very persuasive touring qualities and was far from being exclusively a sports machine.

Meanwhile the 328 Roadsters had become so dominant while their engines had been systematically tuned to deliver a great deal more than the original 80 bhp, that BMW was able to set its sights on overall victory in all classes at international race events. The lightweight BMW 328's were now pitting their strength against bolides which frequently drew twice as much output from three or four-litre engines. BMW countered this raw power with lighter and more streamlined bodywork.