Honda NR 500

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Takazumi Katayama's machine from 1980
Honda oval piston engine 500 cc

The Honda NR 500 from 1979 was a racing motorcycle from the Japanese motorcycle manufacturer Honda , which was powered for the first time by an internal combustion engine with oval pistons.

History and technology

The motorcycle world championship in the class up to 500 cc has been dominated by racing motorcycles with two-stroke engines since 1975 . Honda, principally more fond of the four-stroke engine , tried to compensate for its superiority (twice as many working cycles per unit of time with the same displacement) with innovative technology. As early as February 1978, development began on a four-stroke racing engine called "NR" (new racing). The regulations of the motorcycle world championship only provided for a displacement and cylinder limitation (four); Honda assumed that the filling and thus the performance could be increased by more valves per combustion chamber . The targets envisaged a maximum speed of 23,000 rpm and an output of 130  hp (96  kW ). This was to be achieved by an oval cylinder that had space for 8 valves and was provided with two connecting rods per piston for mass balancing . The oval or arena piston engine , with its superelliptical piston shape (the piston length was 134.3 mm, the width 41 mm and the stroke 24 mm) and the ring tension of the piston rings, posed challenges for the engineers.

The water-cooled four-cylinder - V-type engine with a 100-degree angle had its trial run in July 1979, the engine produced 100 horsepower (74 kW) at 16,000 / min. Honda signed Mick Grant and Takazumi Katayama for the current 1979 season ; the first race took place at the Grand Prix of Great Britain in Silverstone . Grant crashed in the first corner and Katayama dropped out with a technical defect. In addition to the slightly higher weight, the stronger engine braking effect had a negative effect on the lap times. The motorcycle was revised for the 1980 season ; In addition to the responsiveness of the engine, durability has been improved and the frame has been converted to 18-inch tires. Katayama managed to get 12th place in the German Grand Prix on the Nürburgring - Nordschleife . For the 1981 season , the engine was revised again (bank angle 90 degrees) and the output increased to 135 hp (99 kW) at 19,000 rpm. Despite the use of titanium and magnesium , there was an additional weight. The lack of power - 10 hp (7 kW) less than the two-stroke competition from Suzuki or Yamaha  - contributed to the fact that Honda discontinued the project that year and relied on two-stroke technology in the premier class: the Honda NS 500 , with the Freddie Spencer became world champion in 1983 .

Nevertheless, Honda continued to develop the oval piston engine and, in 1987, tried again with the Honda NR 750 at the Le Mans 24-hour motorcycle race . In 1991 Honda presented a limited and commercially available production motorcycle with an oval piston engine, the Honda NR 750 , to the press.

Remarks

  1. ↑ Stefan Zima differentiates in his book Unusual Motors (Vogel-Verlag, Würzburg, 3rd edition 2010, ISBN 978-3- 8343-3140-3) between oval pistons and the arena-shaped pistons of the Honda NR; accordingly, the arena cross-sectional shape corresponds approximately to a centrally cut circle, the semicircles being drawn out and connected in a straight line; In the article Superellipse this corresponds roughly to the green case n = 5 in the drawing. Oval pistons (shape: ellipse with axis lengths 76.5 mm and 99.95 mm) were tested at VW in a diesel test engine with 2.3 L displacement (Auto, Motor and Sport 14, 1990).

Web links

Commons : Honda NR 500  - Collection of pictures, videos and audio files

Individual evidence

  1. ↑ honda.com 1979 Grand Prix, page 3.
  2. ↑ honda.com 1979 Grand Prix, page 5.
  3. ↑ Stefan Zima, Reinhold Ficht: Unusual engines . 3rd edition, Vogel-Buchverlag, Würzburg 2010, ISBN 978-3-8343-3140-3 , p. 90.
  4. ↑ honda.com 1979 Grand Prix, page 7.