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Junkers for Asia

OPPOSED-PISTON ENGINE Increasingly lower costs, consumption, exhaust emissions and weight – these are the most important goals of manufacturers as they continue to develop the internal combustion engine. Employing the well-known opposed-piston principle but brand-new technology, IVM Automotive has built a two-cylinder engine which promises big reductions in all the above values.

CARBON-ALUMINUM PISTON

With a 25 percent lower mass and 300 percent higher temperature resistance than conventional pistons, the carbon-aluminum pistons are the ideal partners in the GKM 1200.

Hugo Junkers’ aircraft engines are to this day the most efficient diesel engines ever built. The creator of the

Junkers 52 (“Auntie Ju”), a flying legend, was the first to recognize the potential inherent in the opposed-piston principle – and this was at the end of the nineteenth century. With its pistons at opposite ends of a common crank- shaft, the one controlling the inlet of fresh air, the other the exhaust of the combustion gases, it’s the only two-stroke cycle that easily outperforms the present-day four-stroke cycle.

And so the specifications of the famed Junkers engines 205 and 207 of the 1930s are sensational even by the standards applied to today’s diesel engines. From 16.6 liters swept volume the JUMO 207, for example, generated 2,200 horsepower, i.e. 133 horsepower

from one liter – at only 3,300 revolutions per minute. Owing to its simple design, consisting of relatively few parts, it also had a unit mass of 309 grams per horsepower and consumed just 155 grams of fuel per horsepower

–advantages that still speak in favor of the opposed-piston principle today. However, it had one serious drawback: a high rate of wear of the exhaust-side pistons, which necessitat- ed short replacement intervals in the old air- craft engines and which renders the principle unsuitable for present-day car engines, pre- cisely because of the high demands on their longevity. This is not to even mention the high pollutant emissions.

JUNKERS REVISITED

Notwithstanding, in the late 1990s, IVM Automotive took up the idea again and improved it using the tools and knowledge of the present, to produce a one-cylinder engine which impressed the engineering world at the 2002 Aachen Colloquium. Together with Diesel -Air, the aircraft engine specialists from Dessau (Junkers’ hometown), IVM Automotive succeeded in completely overcoming the weaknesses of the old opposed-piston engine using advanced development, manufacturing and materials technology. In the meantime two two-cylinder working prototypes have been built of the so-called GKM 1200: each displaces about 1,200 cubic centimeters and develops 70 kW output with 250 Newton meters torque (illustration). The distinctive and decisive features of these joint develop-

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