The Mazda RX-7
The Mazda RX-7 is a front-engine, rear-drive sports car manufactured and marketed by Mazda from 1978-2002 across three generations – all noted for using a compact, lightweight Wankel rotary engine.
The design was conceived by German engineer Felix Wankel. Wankel received his first patent for the engine in 1929. He began development in the early 1950s at NSU, completing a working prototype in 1957. NSU subsequently licensed the design to companies around the world, who have continually added improvements. The engines produced are of spark ignition, with compression ignition engines having only been built in research projects.
Mazda RX-7 Concept and Design
The Wankel engine has the advantages of compact design and low weight over the most commonly used internal combustion engine employing reciprocating pistons. These advantages have given rotary engine applications in a variety of vehicles and devices, including: automobiles, motorcycles, racing cars, aircraft, go-karts, jet skis, snowmobiles, chainsaws, and auxiliary power units. The power-to-weight ratio has reached over one horsepower per pound in certain engines.
History of the RX-7
In 1951, NSU Motorenwerke AG in Germany began development of the engine, with two models being built. The first, the DKM motor, was developed by Felix Wankel. The second, the KKM motor, developed by Hanns Dieter Paschke, was adopted as the basis of the modern Wankel engine.
The basis of the DKM type of motor was that both the rotor and the housing spun around on separate axes. The DKM motor reached higher revolutions per minute and was more naturally balanced. However, the engine needed to be stripped to change the spark plugs and contained more parts. The KKM engine was simpler, having a fixed housing.
The first working prototype, DKM 54, produced 21 hp (16 kW) and ran on February 1, 1957, at the NSU research and development department Versuchsabteilung TX.
The KKM 57 (the Wankel rotary engine, Kreiskolbenmotor) was constructed by NSU engineer Hanns Dieter Paschke in 1957 without the knowledge of Felix Wankel, who later remarked “you have turned my race horse into a plow mare