All Mazda Wankel “rotary” engines are essentially a single family – 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. This is the engine family that made Mazda famous.
In auto racing and 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.
Mazda’s first prototype Wankel was the 40A, a single-rotor engine very much like the NSU KKM400. Although never produced in volume, the 40A was a valuable testbed for Mazda engineers, and quickly demonstrated two serious challenges to the feasibility of the design: “chatter marks” in the housing and heavy oil consumption. The chatter marks, nicknamed “devil’s fingernails”, were caused by improper sealing at the apex of the rotor. The oil consumption problem was addressed with heat-resistant rubber oil seals at the sides of the rotors. This early engine had a rotor diameter of 90 mm (3.5 in), an offset of 14 mm (0.6 in), and a depth of 59 mm (2.3 in).
The very first Mazda Cosmo prototype used a 798 cc L8A two-rotor Wankel. The engine and car were both shown at the 1963 Tokyo Motor Show. Hollow cast iron apex seals reduced vibration and thus chatter marks. It used dry-sump lubrication. Rotor diameter was up from the 40A to 98 mm (3.9 in), but depth dropped to 56 mm (2.2 in).
One-, three-, and four-rotor derivatives of the L8A were also created for experimentation..
The 10A series was Mazda’s first production Wankel, appearing in 1965. It was a two-rotor design, with each displacing 491 cc for a total of 982 cc. These engine featured the mainstream rotor dimensions with a 60 mm (2.4 in) depth.
The rotor housing was made of sand-cast aluminum plated with chrome, while the aluminum sides were sprayed with molten carbon steel for strength. Cast iron was used for the rotors themselves, and their eccentric shafts were of expensive chrome-molybdenum steel. The addition of aluminum/carbon apex seals addressed the chatter mark problem.
The first 10A engine was the 0810, used in the Series I Cosmo from May, 1965 through July, 1968. These cars, and their revolutionary engine, were often called L10A models. Gross output was 110 hp (82 kW) at 7000 RPM and 130 Nm (96 ft.lbf) at 3500 RPM, but both numbers were probably optimistic.
The 10A featured twin side intake ports per rotor, each fed by a one of four carburetor barrels. Only one port per rotor was used under low loads for added fuel economy. A single peripheral exhaust port routed hot gas through the coolest parts of the housing, and engine coolant flowed axially rather than the radial flow used by NSU. A bit of oil was mixed with the intake charge for lubrication.
The 0810 was modified for the racing Cosmos used at Nürburgring. These engines had both side- and peripheral-located intake ports switched with a butterfly valve for low- and high-RPM use (respectively).
1965-1968 Mazda Cosmo Series I/L10A
The improved 0813 engine appeared in July, 1968 in the Series II/L10B Cosmo. Its construction was very similar to the 0810, but the ports and carburetion were revised to produce 128 hp (96 kW) at 7000 RPM and 140 Nm (103 ft.lbf) at 5000 RPM. Again, these were Japanese net output figures.
1968-1972 Mazda Cosmo Series II/L10B
The 10A was substantially revised for wide-scale production in the R100/Familia Rotary. Many changes were made in an effort to reduce production costs. These included the use of cast iron in the housing sides, less-expensive molded (instead of sand-cast) aluminum for the housings, and chrome-steel for the eccentric shafts. The port arrangement remained the same, but exhaust was no longer routed around the housing.
Japanese-spec gross output of the 0820 was 100 hp (75 kW) at 7000 RPM and 98 ft.lbf (133 Nm) at 3500 RPM. The use of less-expensive components raised the weight of the engine from 224 lb (102 kg) to 268 lb (122 kg).
1968-1973 Mazda R100/Familia Rotary
The final member of the 10A family was the 1971 0866. This variant featured a cast-iron thermal reactor to reduce exhaust emissions and re-tuned exhaust ports. The die-cast rotor housing was now coated with a new process: The new Transplant Coating Process (TCP) featured sprayed-on steel which is then coated with chrome. Gross output was 105 hp (78 kW) at 7000 RPM and 135 Nm (99.5 ft.lbf) at 3500 RPM.
1972-1974 Mazda RX-3 (Japan-spec)
The 13A was designed especially for front wheel drive applications. It had two 655 cc rotors for a total of 1310 cc. This was the only production Mazda Wankel with different rotor dimensions: Diameter was 120 mm (4.7 in) and offset was 17.5 mm (0.7 in), but depth remained the same as the 10A at 60 mm (2.4 in). Another major difference from the previous engines was the integrated water-cooled oil cooler.
The 13A was used only in the 1969-1972 R130 Luce, where it produced 126 hp (94 kW) and 126 ft.lbf (172 Nm). This was the end of the line for this engine design: The next Luce was rear wheel drive and Mazda never again made a front wheel drive rotary vehicle.
1970-1972 Mazda R130 Luce
The 12A was a “bored-out” version of the 10A – the rotor diameter was the same, but the depth was increased by 10 mm (0.4 in) to 70 mm (2.8 in). Each of its two rotors displaced 573 cc for a total of 1146 cc. The 12A series was produced for 15 years, from May 1970 through 1985. In 1974, a 12A became the first engine built outside of western Europe or the U.S to finish the 24 hours of Le Mans.
In 1974, a new process was used to harden the rotor housing. The Sheet-metal Insert Process (SIP) used a sheet of steel much like a conventional piston engine cylinder liner with a chrome plated surface. The side housing coating was also changed to eliminate the troublesome sprayed metal. The new “REST” process created such a strong housing, the old carbon seals could be abandoned in favor of conventional cast iron.
Early 12A engines also feature a thermal reactor, similar to the 0866 10A, and some use an exhaust port insert to reduce exhaust noise. A lean-burn version was introduced in 1979 (in Japan) and 1980 (in America) which substituted a more-conventional catalytic converter for this “afterburner”. A major modification of the 12A architecture was the 6PI which featured variable induction ports.
1970-1972 Mazda R100
1970-1974 Mazda RX-2, 130 hp (97 kW) and 115 ft.lbf (156 Nm)
1972-1974 Mazda RX-3 (Japan), 110 hp (82 kW) and 100 ft.lbf (135 Nm)
1972-1974 Mazda RX-4
1972-1980 Mazda Luce
1978-1979 Mazda RX-7, 100 hp (75 kW)
1979-1985 Mazda RX-7 (Japan)
1980-1985 Mazda RX-7 (USA)
1981-1985 Mazda Luce
1981-1985 Mazda Cosmo
The ultimate 12A engine was the turbocharged and fuel injected engine used in the Japan-spec Cosmo, Luce, and RX-7. It featured “semi-direct injection” into both rotors at once, a technique that was much more successful than it would appear. A passive knock sensor was used to eliminate detonation, and later models featured a specially-designed “impact turbo” which was tweaked for the unique exhaust signature of the Wankel engine. Output was 132 hp (98 kW) at 6000 RPM and 186 Nm (137 ft.lbf) at 4000 RPM.
1983-1985 Mazda Cosmo
1983-1985 Mazda Luce
1984-1985 Mazda RX-7
The improved 12B was quietly introduced in 1974. It featured dual distributors like the original 10A.
1974-1978 Mazda RX-2
1974-1978 Mazda RX-3
The 13B is the most widely-produced engine. It was the basis for all future Mazda wankel engines, and was produced for almost 30 years. The 13B is no relation to the 13A. Instead, it is a lengthened version of the 12A, having 80 mm (3.1 in) thick rotors. It had the largest displacement yet at 654 cc, for a total of 1308 cc.
In the United States, the 13B was available from 1974 through 1978 and was then retired until the 1983 RX-7 GSL-SE. It was retired again in 1996 with the cancellation of the RX-7. The engine was continually used in Japan from 1972’s Mazda Luce/RX-4 through 2002’s RX-7.
The 13B was designed with both high performance and low emissions in mind. Early vehicles using this engine used the AP name, which signified these two characteristics.
1972-1980 Mazda Cosmo AP
1974-1977 Mazda Rotary Pickup
1975-1977 Mazda Roadpacer
1974-1978 Mazda RX-4
A tuned intake manifold was used in a Wankel engine for the first time with the 13B-DEI. The so-called Dynamic Effect Intake featured a two-level intake box which derived a supercharger-like effect from the Helmholtz resonance of the opening and closing intake ports. The DEI engine also featured Bosch L-Jetronic fuel injection. Output was much improved at 135 hp (101 kW) and 133 ft.lbf (180 Nm).
1981-1985 Mazda Luce
1981-1989 Mazda Cosmo
1984-1985 Mazda RX-7 GSL-SE
Like the 12A-6PI, the second-generation RX-7 bowed with a variable-intake system. Dubbed VDEI, the engine features both the 6PI and DEI systems, as well as dual-injector electronic fuel injection. Total output is up to 146 hp (109 kW) at 6500 RPM and 138 ft.lbf (187 Nm) at 3500 RPM.
1986-1988 Mazda RX-7, 146 hp (108 kW)
1989-1991 Mazda RX-7, 160 hp (119 kW) 13B-Turbo
The 13B-DEI was turbocharged in 1986. It features the newer dual-injector fuel injection of the 6PI engine, but lacks that engine’s eponymous variable intake system. The twin-scroll turbocharger is fed with a two-stage valve to reduce turbo lag. Output is way up at 189 hp (141 kW) at 6500 RPM and 183 ft.lbf (248 Nm) at 3500 RPM.
1986-1989 Mazda Luce
1987-1989 Mazda RX-7 Turbo-II, 189 hp (141 kW)
1990-1991 Mazda RX-7 Turbo-II, 200 hp (149 kW)
A twin-turbocharged version of the 13B, the 13B-REW, became famous for its high output and low weight. The turbos were arranged sequentially, with a smaller unit providing low pressure and the larger one activated at higher RPM. Output eventually reached, and may have exceeded, Japan’s “maximum” of 276 hp (206 kW).
1990-1995 Eunos Cosmo
1993-1997 Mazda RX-7, 255 hp (190 kW)
1998-2002 Mazda RX-7, 276 hp (206 kW)
Eunos Cosmo engine at the Mazda MuseumIn Le Mans racing, the first three-rotor engine used in the 757 was named the 13G. It was renamed 20B after Mazda’s naming convention for the 767 in November of 1987. The three-rotor 20B-REW was only used in the 1990-1996 Eunos Cosmo. It was a twin-turbo setup and was based on the 13B-RE engine found in the standard model Cosmo. It displaced 1962 cc (three 654 cc rotors) and used .7 bar of turbo pressure to produce 295 hp (220 kW) and 289 ft.lbf (392 Nm).
The first Mazda four-rotor engine was the 13J used in the 1988 767 Le Mans prototypes. It was closely related to the 13G used previously and the later 26B.
The most prominant 4-rotor engine from Mazda was used exclusively for various Mazda-built GT cars (including the 767 and 787B) in replacement of the older 13J. In 1991 this engine in a 787B became the first from outside the U.S. or Western Europe to win the 24 hours of Le Mans race. It displaced 2622 cc and built 700 hp (522 kW) at 9000RPM. The engine design originates as two 13B’s melded together with continually variable geometry intakes. The 26B’s engine block can be purchased at retail from Mazdaspeed, but no internal parts are available to the general public.
The Renesis was an evolution of the 13B and first appeared (in production) in the 2004 Mazda RX-8. The Renesis 13B is very different from all previous Mazda production Wankels (except the 10A) in one major respect: The exhaust ports are now on the side rather than the periphery of the rotor housing. This eliminates the exhaust overlap problem, improving power and reducing emissions. The naturally aspirated Renesis produces an amazing 238 hp (178 kW) – compare this to 255 hp (190 kW) for the twin turbocharged 13B in the Mazda RX-7.
The Renesis engine won International Engine of the Year and Best New Engine awards 2003. It also holds the “2.5 to 3 liter” size award for 2003 and 2004, where it is considered a 2.6 L engine. Finally, it was on the Ward’s 10 Best Engines list for 2004 and 2005.