Honda Revolutionizes 4-Stroke Engine Design

In 1978, one year after Honda announced its intention to return to WGP the NR (New Racing) development team was established, and full scale development of the new machine began. Honda had three stated goals for their return to racing. First, to showcase Honda technology by winning races. Second, to create revolutionary technology. And third, to bring up a new generation of engineers and designers inspired with the racing spirit. The development team members were all young and full of new ideas.

"We wanted to create a machine that epitomized the ultimate in advanced technology," says President Fukui. "An engine that would shock the world. At the time, 2-strokes dominated racing, and both 2-strokes and 4-strokes were limited to 500cc and four cylinders." Conventional wisdom was that a 4-stroke simply couldn't compete under these regulations. But with Honda's reputation for building 4-strokes, the development team was determined to show the world what they could do. The battle to revolutionize 4-stroke technology had begun!

1979 NR500(0X) Engine

1979 NR500(0X) Engine

1979 NR500(0X) Engine

1979 NR500(0X) Engine

1980 NR500(1X) Engine & Frame

Imagination and Unconventional Ideas Create a Revolutionary V4 Engine

In simplest terms, in order for a 4-stroke to compete with a 2-stroke under the existing regulations it would have to spin at twice the rpm. Thus, a valve train that could survive at ultra-high rpm would have to be invented, and intake efficiency would have to be dramatically increased. To meet these seemingly impossible conditions the engineers came up with a breakthrough idea. They would double the number of valves per cylinder from the usual four, to eight. To ensure high combustion efficiency, they developed oval pistons. Of course, oval piston rings and other new technologies also had to be created, and extensive tests were needed. Six months after this preliminary design work, development of the actual engine began and the first drawings of the revolutionary oval-piston engine were created. Featuring a 100° V-angle, the liquid-cooled DOHC Four was designated the OX engine. The engine used a reduced number of crank journals to reduce frictional loss for high power output. An opposed piston layout reduced primary crankshaft vibration. A slim and very compact design contributed to mass centralization, resulting in very responsive handling. By freeing themselves from the conventional wisdom that 'pistons should be round,' Honda's engineers were able to create a unique and revolutionary V4 engine.

1981 NR500(2X) Cylinder head

1981 NR500(2X) Cylinder head


1981 NR500(2X) Cylinder head

1981 NR500(2X) Piston

1981 NR500(2X) Piston


1981 NR500(2X) Piston

1981 NR500(2X) Engine

1981 NR500(2X) Engine


1981 NR500(2X) Engine

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