The Mazda Wankel engines (a type of rotary combustion engine) are family of car engines derived from experiments in the early 1960s by Felix Wankel, a German engineer. Over the years, displacement has been increased and turbocharging has been added.
Wankel engines can be classified by their geometric size in terms of radius (rotor center to tip distance, also the median stator radius) and depth (rotor thickness), and offset (crank throw, eccentricity, also 1/4 the difference between stator's major and minor axes). These metrics function similarly to the bore and stroke measurements of a piston engine. Displacement is 3√3radius·offset·depth, multiplied with the number of rotors (note that this only counts a single face of each rotor as the entire rotor's displacement). Nearly all Mazda production Wankel engines share a single rotor radius, 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) rotor radius and 17.5 mm (0.7 in) crankshaft offset.
Mazda rotary engines have a reputation for being relatively small and powerful at the expense of poor fuel efficiency. They are starting to become popular with kit car builders, hot rodders and in light aircraft because of their light weight, compact size, and tuning potential stemming from their inherently high power to weight ratio[citation needed].
In auto racing, the displacement of a Wankel engine is usually doubled for classing purposes. For calculating taxes in Japan, the displacement of Wankel engines is defined as the equivalent of 1.5 times the nominal displacement, so the 1300 cc 13B engines are taxed as 1950 cc.
When Wankel engines became commonplace in motor sport events, this created the problem of accurate representation of each engine's displacement, for the benefit of competition. Rather than force the majority of participants (driving piston engine cars) to half their quoted displacement (likely resulting in confusion), most racing organizations simply decided to double the quoted displacement of Wankel engines.
The 13B is the most widely produced engine. It was the basis for all future Mazda Wankel engines, and was produced for over 30 years. The 13B has no relation to the 13A. Instead, it is a lengthened version of the 12A, having 80 mm (3.1 in) thick rotors. Each rotor had a displacement of 654 cc, for a total of 1308 cc displacement in the engine.
In the United States, the 13B was available from 1974 through 1978 and was then retired until the 1984 RX-7 GSL-SE. It disappeared from the US market again in 1995, when the last US-spec RX-7s were sold. The engine was continually used in Japan from 1972's Mazda Luce/RX-4 through 2002's RX-7.
AP
The 13B was designed with both high performance and low emissions in mind. Early vehicles using this engine used the AP name.
Applications:
1975–1980 Mazda Cosmo AP
1974–1977 Mazda Rotary Pickup
1975–1977 Mazda Roadpacer
1973–1978 Mazda RX-4
1975–1980 RX-5
13B-RESI
A tuned intake manifold was used in a Wankel engine for the first time with the 13B-RESI. RESI = Rotary Engine Super Injection. 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 RESI engine also featured Bosch L-Jetronic fuel injection. Output was much improved at 135 hp (101 kW) and 180 N·m (133 ft·lbf).
Applications:
1984–1985 Mazda HB Luce
1984–1985 Mazda HB Cosmo
1984–1985 Mazda FB RX-7 GSL-SE
13B-DEI
Like the 12A-SIP, the second-generation RX-7 bowed with a variable-intake system. Dubbed DEI, the engine features both the 6PI and DEI systems, as well as four-injector electronic fuel injection. Total output is up to 146 hp (109 kW) at 6500 rpm and 187 N·m (138 ft·lbf) at 3500 rpm.
The 13B-DEI was turbocharged in 1986. It features the newer four-injector fuel injection of the 6PI engine, but lacks that engine's eponymous variable intake system. In '86-'88 engines the twin-scroll turbocharger is fed using a two-stage mechanically actuated valve, however on '89-'91 engines a better turbo design was used with a divided manifold powering the twin-scroll configuration. For engines manufactured between '86-'88 output is rated at 185 hp (138 kW) at 6500 rpm and 248 N·m (183 ft·lbf) at 3500 rpm.
Applications:
1986–1988 Mazda FC3S S4 RX-7, 146 hp (108 kW)
1989–1991 Mazda FC3S S5 RX-7, 160 hp (119 kW)
Applications:
1986–1991 Mazda HC Luce Turbo-II, 185 hp (138 kW)
1986–1988 Mazda FC3S S4 Turbo RX-7 Turbo-II, 185 hp (138 kW)
1989–1991 Mazda FC3S S5 Turbo RX-7 Turbo-II, 200 hp (147 kW)
13B-REW
The 13B-REW was first series production twin sequential turbo systems to be offered for sale. Often mis-represented as a 13B-RE due to this symbol being cast into its upper manifold. The 13B-REW from the JC Cosmo series was endowed with the largest side ports of any later model rotary engine.
Compared to the twin turbos fitted to the 13B-REW on the FD RX-7, these sequential turbos received a large (HT-15) primary with a smaller (HT-10) secondary turbo. Injector sizes = 550cc PRI + SEC.
Approximately 5000 13B-REW optioned JC Cosmos were sold making this engine almost as hard to source as its rarer 20B-REW big-brother.[citation needed].
Applications:
1990–1995 Eunos Cosmo, 235 hp (176 kW; 238 PS)
A twin-turbocharged version of the 13B, the 13B-REW, became famous for its high output and low weight]. The twin Hitachi HT-12 turbos were operated sequentially, with the primary providing boost until 4,500 rpm, and the secondary coming online afterwards. Output eventually reached, and may have exceeded, Japan's unofficial maximum of 280 DIN hp (206 kW) for the final revision used in the series 8 Mazda RX-7.
Applications:
1992–1995 Mazda RX-7, 255 hp (190 kW)
1996–1998 Mazda RX-7, 265 hp (197 kW)
1999–2002 Mazda RX-7, 280 hp (206 kW)
