Mazda Car Engines: Used & Reconditioned Mazda Engines, MX5, Cosmo, Rotary Pickup, Roadpacer
They all derive from the first Wankel experiments in the early 1960s. Over the years, displacement has been increased (somewhat), and turbocharging has been added to great effect. Mazda is the family car engine that made Mazda famous, Reconditioned, Used or Secondhand they can be found at Engines and Gearboxes.
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In auto racing, the displacement of a Wankel engine is usually doubled for classing purposes. For Japanese tax purposes, the displacement of Wankel engines is defined as the equivalent of 1.5 times the nominal displacement. So the 1.3 L 13B engines count as just under 2.0 L for these purposes.
Wankel engines can be classified by their rotor size in terms of width (diameter) and depth (thickness). These metrics function similarly to the bore and stroke measurements of a piston engine. Nearly all Mazda production Wankel engines share a single rotor diameter: 105 mm (4.1 in) with a 15 mm (0.6 in) crankshaft offset. The only engine to diverge from this formula was the rare 13A, which used a 120 mm (4.7 in) diameter and 17.5 mm (0.7 in) offset.
The Wankel rotary engine
It’s a type of internal combustion engine, invented by German engineer Felix Wankel, which uses a rotor instead of reciprocating pistons.
This design delivers smooth high-rpm power from a compact, lightweight engine. In the Wankel engine, the four strokes of a typical Otto cycle occur in the space between a rotor, which is roughly triangular, and the inside of a housing. In the basic single-rotor Wankel engine, the oval-like epitrochoid-shaped housing surrounds a three-sided rotor (similar to a Reuleaux triangle, a three-pointed curve of constant width, but with the middle of each side a bit more flattened). The central drive shaft, also called an eccentric shaft or E-shaft, passes through the center of the rotor and is supported by bearings. The rotor both rotates around an offset lobe (crank) on the E-shaft and makes orbital revolutions around the central shaft. Seals at the corners of the rotor seal against the periphery of the housing, dividing it into three moving combustion chambers. Fixed gears mounted on each side of the housing engage with ring gears attached to the rotor to ensure the proper orientation as the rotor moves.
As the rotor rotates and orbitally revolves, each side of the rotor gets closer and farther from the wall of the housing, compressing and expanding the combustion chamber similarly to the strokes of a piston in a reciprocating engine. The power vector of the combustion stage goes through the center of the offset lobe.
While a four-stroke piston engine makes one combustion stroke per cylinder for every two rotations of the crankshaft (that is, one half power stroke per crankshaft rotation per cylinder), each combustion chamber in the Wankel generates one combustion stroke per each driveshaft rotation, i.e. one power stroke per rotor orbital revolution and three power strokes per rotor rotation. Thus, power output of a Wankel engine is generally higher than that of a four-stroke piston engine of similar engine displacement in a similar state of tune and higher than that of a four-stroke piston engine of similar physical dimensions and weight. Wankel engines also generally have a much higher redline than a reciprocating engine of similar size since the strokes are completed with a rotary motion as opposed to a reciprocating engine which must use connecting rods and a crankshaft to convert reciprocating motion into rotary motion.
National agencies that tax automobiles according to displacement and regulatory bodies in automobile racing variously consider the Wankel engine to be equivalent to a four-stroke engine of 1.5 to 2 times the displacement; some racing regulatory agencies view it as offering such a pronounced advantage that they ban it altogether. After Mazda won the 24 hours of Le Mans in 1991 with their 787B car powered by a 4-rotor Wankel engine, the FIA (Federation Internationale de l’Automobile) decided to ban rotary-engine cars from racing in that league.
The most extensive automotive use of the Wankel engine has been by the Japanese company Mazda.
After years of development, Mazda’s first Wankel engined car was the 1967 Mazda Cosmo. Mazda later abandoned the Wankel in most of their automotive designs, but continued using it in their RX-7 sports car until August of 2002. In 2003, Mazda introduced the RENESIS engine with the new RX-8. The RENESIS engine relocated the ports for exhaust and intake from the periphery of the rotary housing to the sides, allowing for larger overall ports, better airflow, and further power gains. The RENESIS is capable of delivering 250 hp from its minute 1.3 L displacement at better fuel economy, reliability, and environmental friendliness than any other Mazda rotary engine in history.
Mazda Wankel rotary timeline:
R100 | RX-2 | RX-3 | RX-4 | RX-5 | Luce | RX-7 | RX-8 | 6PI | Cosmo | Rotary Pickup | Roadpacer | Savanna | Capella | Familia | Proceed.