title: Wankel engine

text: In the Wankel engine, the four stages of an Otto cycle occur in the space between each face of a three-sided symmetrical rotor and the inside of a static oval-like epitrochoid-shaped outer housing. The triangular rotor with bow-shaped faces is similar in appearance to a Reuleaux triangle. The shape of the rotor between the fixed apexes is to minimize the volume of the geometric combustion chamber and maximize the compression ratio, respectively. The symmetric curve connecting two apices of the rotor is determined by the inner housing shape ensuring the rotor does not touch the housing at any angle of rotation.


title: Wankel engine

text: The central output shaft, called the "eccentric shaft" or "E-shaft", passes through the center of the housing being supported by fixed bearings. The rotor rides on eccentrics which is analogous to crankpins in piston engine, an integral part of the eccentric shaft, which is analogous to a crankshaft. The rotor rotates around the eccentric output shaft in a hula-hoop movement. Seals at the apices of the rotor seal against the periphery of the housing, dividing it into three moving combustion chambers. The rotation of the rotor on its own axis is caused and controlled by a pair of synchronizing gears A fixed gear mounted on one side of the rotor housing engages a ring gear attached to the rotor and ensures the rotor moves exactly one-third turn for each turn of the eccentric output shaft. The power output of the engine is not transmitted through the synchronizing gears. The rotor moves in its rotating motion guided by the gears and the eccentric output shaft, not being guided by the external chamber. The rotor does not make contact against the external engine housing. The force of expanded gas pressure on the rotor exerts pressure to the center of the eccentric part of the output shaft.


title: Wankel engine

text: The easiest way to visualize the action of the engine in the animation is to look not at the rotor itself, but at the cavity created between it and the housing. The Wankel engine is actually a variable-volume progressing-cavity system. Thus, the three cavities per housing all repeat the same cycle. Points A and B on the rotor and E-shaft turn at different speeds—point B circles three times as often as point A does, so that one full orbit of the rotor equates to three turns of the E-shaft.


title: Wankel engine

text: As the rotor rotates orbitally in a hula-hoop fashion, each side of the rotor is brought closer to and then away from the wall of the housing, compressing and expanding the combustion chamber. Analogous to a piston in a reciprocating piston engine. The power vector of the combustion stage goes through the center of the offset lobe.


title: Wankel engine

text: While a four-stroke piston engine completes 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 driveshaft rotation, i.e. one power stroke per rotor output shaft revolution and three power strokes per rotor rotation. Thus, the 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, giving a higher power to weight ratio. Wankel engines ideally can reach much higher engine revolutions than reciprocating engines of similar power output. This is due partly to the smoothness inherent in its circular motion, the lack of a mechanical valvetrain employing reciprocating poppet valves, and the rotor spinning at one-third of the speed of the output shaft.


title: Wankel engine

text: The eccentric output shafts do not have the stress-related contours of crankshafts. The maximum revolutions of a Wankel engine are limited by tooth load on the synchronizing gears. Hardened steel gears are used for extended operation above 7000 or 8000 rpm. In practice, Wankel engines in production automobiles are not operated at much higher output shaft speeds than reciprocating piston engines of similar output power, and cycle speeds (one-third of Wankel output shaft speed and one-half of four-stroke crankshaft speed) are similar to conventional engines; for example, the "12A" Wankel in the 1970 RX-2 produced peak power at 7,000 RPM (39 engine cycles per second), while the reciprocating piston engine in the same year of the same model family (Capella) produced peak power at 6,000 RPM (50 engine cycles per second). Mazda Wankel engines in auto racing are operated above 10,000 rpm, but so are four-stroke reciprocating piston engines of relatively small displacement per cylinder. In aircraft, they are used conservatively, up to 6500 or 7500 rpm, but as gas pressure participates in seal efficiency, racing a Wankel engine at high revolutions under no-load conditions can destroy the engine.


title: Wankel engine

text: Three lobes exist per rotor (because the rotor is completing only one-third rotation per one rotation of the output shaft, so only one power stroke occurs per working per output revolution, the other two lobes are simultaneously ejecting a spent charge and taking in a new one, rather than contributing to the power output of that revolution). Some racing series have banned the Wankel altogether, along with all other alternatives to the traditional reciprocating-piston, four-stroke design.


title: Wankel engine

text: In a Wankel rotary engine, the chamber volume formula_1 is equivalent to the product of the rotor surface formula_2 and the rotor path formula_3. The rotor surface formula_2 is given by the rotor tips' path across the rotor housing and determined by the generating radius formula_5, the rotor width formula_6, and the distance between the rotor tips and the rotor housing formula_7. Since the rotor has a trochoid ("triangualar") shape, sinus 60 degrees describes the interval at which the rotor tips get closest to the rotor housing. Therefore,


title: Wankel engine

text: In a Wankel rotary engine, the eccentric shaft needs to make three full rotations (1080°) per combustion chamber in order to complete all four cycles of a four cycle engine. Since a Wankel rotary engine has three combustion chambers, all four cycles of a four cycle engine are completed within one full rotation of the eccentric shaft (360°). This is different from a four cycle piston engine, which needs to make two full rotations per combustion chamber in order to complete all four cycles of a four cycle engine. Therefore, in a Wankel rotary engine, the chamber volume has to be doubled in order to obtain the displacement formula_13:


title: Wankel engine

text: with formula_15 being the number of rotors per engine. The Wankel rotary engine's displacement formula_13 is equivalent to a piston engine's displacement formula_13.


title: Wankel engine

text: NSU licensed the design to companies around the world, with many companies implementing continual improvements. In 1960, NSU and the US firm Curtiss-Wright, signed a joint agreement. NSU was to concentrate on low and medium-powered Wankel engine development, with Curtiss-Wright developing high-powered engines, including aircraft engines of which Curtiss-Wright had decades of experience designing and producing. Curtiss-Wright recruited Max Bentele to head their design team.


title: Wankel engine

text: Many manufacturers signed license agreements for development, attracted by the smoothness, quiet running, and reliability emanating from the uncomplicated design. Among them were Alfa Romeo, American Motors, Citroën, Ford, General Motors, Mazda, Mercedes-Benz, Nissan, Porsche, Rolls-Royce, Suzuki, and Toyota. In the United States in 1959, under license from NSU, Curtiss-Wright pioneered improvements in the basic engine design. In Britain, in the 1960s, Rolls Royce's Motor Car Division pioneered a two-stage diesel version of the Wankel engine.


title: Wankel engine

text: Deere & Company designed a version that was capable of using a variety of fuels. The design was proposed as the power source for United States Marine Corps combat vehicles and other equipment in the late 1980s.


title: Wankel engine

text: In 1961, the Soviet research organization of NATI, NAMI, and VNIImotoprom commenced development creating experimental engines with different technologies. Soviet automobile manufacturer AvtoVAZ also experimented in Wankel engine design without a license, introducing a limited number of engines in some cars.


title: Wankel engine

text: By mid-September 1967, even Wankel model engines became available through the German Graupner aeromodelling products firm, made for them by O.S. Engines of Japan.


title: Wankel engine

text: Despite much research and development throughout the world, only Mazda has produced Wankel engines in large quantities.


title: Wankel engine

text: Felix Wankel managed to overcome most of the problems that made previous attempts to perfect the rotary engines fail, by developing a configuration with vane seals having a tip radius equal to the amount of "oversize" of the rotor housing form, as compared to the theoretical epitrochoid, to minimize radial apex seal motion plus introducing a cylindrical gas-loaded apex pin which abutted all sealing elements to seal around the three planes at each rotor apex.


title: Wankel engine

text: In the early days, special, dedicated production machines had to be built for different housing dimensional arrangements. However, patented designs such as , G. J. Watt, 1974, for a "Wankel Engine Cylinder Generating Machine", , "Apparatus for machining and/or treatment of trochoidal surfaces" and , "Device for machining trochoidal inner walls", and others, solved the problem.


title: Wankel engine

text: Wankel engines have a problem not found in reciprocating piston four-stroke engines in that the block housing has intake, compression, combustion, and exhaust occurring at fixed locations around the housing. In contrast, reciprocating engines perform these four strokes in one chamber, so that extremes of "freezing" intake and "flaming" exhaust are averaged and shielded by a boundary layer from overheating working parts. The use of heat pipes in an air-cooled Wankel was proposed by the University of Florida to overcome this uneven heating of the block housing. Pre-heating of certain housing sections with exhaust gas improved performance and fuel economy, also reducing wear and emissions.


title: Wankel engine

text: The boundary layer shields and the oil film act as thermal insulation, leading to a low temperature of the lubricating film (approximate maximum on a water-cooled Wankel engine. This gives a more constant surface temperature. The temperature around the spark plug is about the same as the temperature in the combustion chamber of a reciprocating engine. With circumferential or axial flow cooling, the temperature difference remains tolerable.


title: Wankel engine

text: Problems arose during research in the 1950s and 1960s. For a while, engineers were faced with what they called "chatter marks" and "devil's scratch" in the inner epitrochoid surface. They discovered that the cause was the apex seals reaching a resonating vibration, and the problem was solved by reducing the thickness and weight of the apex seals. Scratches disappeared after the introduction of more compatible materials for seals and housing coatings. Another early problem was the build-up of cracks in the stator surface near the plug hole, which was eliminated by installing the spark plugs in a separate metal insert/ copper sleeve in the housing, instead of a plug being screwed directly into the block housing. Toyota found that substituting a glow-plug for the leading site spark plug improved low rpm, part load, specific fuel consumption by 7%, and also emissions and idle. A later alternative solution to spark plug boss cooling was provided with a variable coolant velocity scheme for water-cooled rotaries, which has had widespread use, being patented by Curtiss-Wright, with the last-listed for better air-cooled engine spark plug boss cooling. These approaches did not require a high-conductivity copper insert, but did not preclude its use. Ford tested a Wankel engine with the plugs placed in the side plates, instead of the usual placement in the housing working surface (, 1978).


title: Wankel engine

text: Increasing the displacement and power of a Wankel engine by adding more rotors to a basic design is simple, with a limitation in the number of rotors, because power output is channeled through the last rotor shaft, with all the stresses of the whole engine present at that point. For engines with more than two rotors, coupling two bi-rotor sets by a serrate coupling (such as a Hirth joint) between the two rotor sets has been tested successfully.


title: Wankel engine

text: Research in the United Kingdom under the SPARCS (Self-Pressurising-Air Rotor Cooling System) project, found that idle stability and economy were obtained by supplying an ignitable mix to only one rotor in a multi-rotor engine in a forced-air cooled rotor, similar to the Norton air-cooled designs.


title: Wankel engine

text: The Wankel engine's drawbacks of inadequate lubrication and cooling in ambient temperatures, short engine lifespan, high emissions, and low fuel efficiencies were tackled by Norton Wankel rotary engine specialist David Garside, who developed three patented systems in 2016.


title: Wankel engine

text: SPARCS and Compact-SPARCS provide superior heat rejection and efficient thermal balancing to optimize lubrication. A problem with Wankel engines is that the engine housing has permanently cool and hot surfaces when running. It also generates excessive heat inside the engine which broke down older lubricating oil quickly. The SPARCS system reduces this wide differential in heat temperatures in the metal of the engine housing, and also cools the rotor from inside the body of the engine. This results in reduced engine wear prolonging engine life. As described in Unmanned Systems Technology Magazine, "SPARCS uses a sealed rotor cooling circuit consisting of a circulating centrifugal fan and a heat exchanger to reject the heat. This is self-pressurized by capturing the blow-by past the rotor side gas seals from the working chambers."


title: Wankel engine

text: CREEV is an ‘exhaust reactor’, containing a shaft & rotor inside, of a different shape to a Wankel rotor. The reactor, located in the exhaust stream outside of the engine's combustion chamber, consumes unburnt exhaust products without using a second ignition system before directing burnt gasses into the exhaust pipe. Horsepower is given to the reactors shaft. Lower emissions and improved fuel efficiency are achieved. All three patents are currently licensed to UK-based engineers, AIE (UK) Ltd.


title: Wankel engine

text: A peripheral intake port gives the highest mean effective pressure; however, side intake porting produces a more steady idle, because it helps to prevent blow-back of burned gases into the intake ducts which cause "misfirings", caused by alternating cycles where the mixture ignites and fails to ignite. Peripheral porting (PP) gives the best mean effective pressure throughout the rpm range, but PP was linked also to worse idle stability and part-load performance. Early work by Toyota led to the addition of a fresh air supply to the exhaust port, and proved also that a Reed-valve in the intake port or ducts improved the low rpm and partial load performance of Wankel engines, by preventing blow-back of exhaust gas into the intake port and ducts, and reducing the misfire-inducing high EGR, at the cost of a small loss of power at top rpm. David W. Garside, the developer of the Norton rotary engine, proposed that earlier opening of the intake port before the top dead center (TDC), and longer intake ducts, improved the low rpm torque and elasticity of Wankel engines. That is also described in Kenichi Yamamoto's books. Elasticity is also improved with a greater rotor eccentricity, analogous to a longer stroke in a reciprocating engine. Wankel engines operate better with a low-pressure exhaust system. Higher exhaust back pressure reduces mean effective pressure, more severely in peripheral intake port engines. The Mazda RX-8 Renesis engine improved performance by doubling the exhaust port area compared with earlier designs, and there have been studies of the effect of intake and exhaust piping configuration on the performance of Wankel engines.


title: Wankel engine

text: Unlike a piston engine, in which the cylinder is heated by the combustion process and then cooled by the incoming charge, Wankel rotor housings are constantly heated on one side and cooled on the other, leading to high local temperatures and unequal thermal expansion. While this places great demands on the materials used, the simplicity of the Wankel makes it easier to use alternative materials, such as exotic alloys and ceramics. With water cooling in a radial or axial flow direction, and the hot water from the hot bow heating the cold bow, the thermal expansion remains tolerable. Top engine temperature has been reduced to , with a maximum temperature difference between engine parts of by the use of heat pipes around the housing and in side plates as a cooling means.


title: Wankel engine

text: Among the alloys cited for Wankel housing use are A-132, Inconel 625, and 356 treated to T6 hardness. Several materials have been used for plating the housing working surface, Nikasil being one. Citroën, Mercedes-Benz, Ford, A P Grazen and others applied for patents in this field. For the apex seals, the choice of materials has evolved along with the experience gained, from carbon alloys, to steel, ferritic stainless, and other materials. The combination between housing plating and apex and side seals materials was determined experimentally, to obtain the best duration of both seals and housing cover. For the shaft, steel alloys with little deformation on load are preferred, the use of Maraging steel has been proposed for this.


title: Wankel engine

text: Leaded gasoline fuel was the predominant type available in the first years of the Wankel engine's development. Lead is a solid lubricant, and leaded gasoline is designed to reduce the wearing of seals and housings. The first engines had the oil supply calculated with consideration of gasoline's lubricating qualities. As leaded gasoline was being phased out, Wankel engines needed an increased mix of oil in the gasoline to provide lubrication to critical engine parts. Experienced users advise, even in engines with electronic fuel injection, adding at least 1% of oil directly to gasoline as a safety measure in case the pump supplying oil to combustion chamber-related parts failed or sucked in air. Lead tetraethyl (TEL) burns in the engine to form carbon dioxide, lead oxide, and water. Since the lead oxide would deposit in the combustion chamber, TEL is used together with ethyl bromide or ethylene chloride, which convert the lead oxide into lead bromide or lead chloride, which evaporate more easily. A SAE paper by David Garside extensively described Norton's choices of materials and cooling fins.


title: Wankel engine

text: Several approaches involving solid lubricants were tested, and even the addition of LiquiMoly (containing MoS), at the rate of per liter of fuel, is advised. Many engineers agree that the addition of oil to gasoline as in old two-stroke engines is a safer approach for engine reliability than an oil pump injecting into the intake system or directly to the parts requiring lubrication. A combined oil-in-fuel plus oil metering pump is always possible.


title: Wankel engine

text: Early engine designs had a high incidence of sealing loss, both between the rotor and the housing and also between the various pieces making up the housing. Also, in earlier model Wankel engines, carbon particles could become trapped between the seal and the casing, jamming the engine and requiring a partial rebuild. It was common for very early Mazda engines to require rebuilding after . Further sealing problems arose from the uneven thermal distribution within the housings causing distortion and loss of sealing and compression. This thermal distortion also caused uneven wear between the apex seal and the rotor housing, evident on higher mileage engines. The problem was exacerbated when the engine was stressed before reaching operating temperature. However, Mazda Wankel engines solved these initial problems. Current engines have nearly 100 seal-related parts.


title: Wankel engine

text: The problem of clearance for hot rotor apexes passing between the axially closer side housings in the cooler intake lobe areas was dealt with by using an axial rotor pilot radially inboard of the oils seals, plus improved inertia oil cooling of the rotor interior (C-W , C. Jones, 5/8/63, , M. Bentele, C. Jones. A.H. Raye. 7/2/62), and slightly "crowned" apex seals (different height in the center and in the extremes of seal).


title: Wankel engine

text: The shape of the Wankel combustion chamber is more resistant to preignition operating on lower-octane rating gasoline than a comparable piston engine. The combustion chamber shape may also lead to incomplete combustion of the air-fuel charge using gasoline fuel. This would result in a larger amount of unburned hydrocarbons released into the exhaust. The exhaust is, however, relatively low in NOx emissions, because combustion temperatures are lower than in other engines, and also because of exhaust gas recirculation (EGR) in early engines. Sir Harry Ricardo showed in the 1920s that for every 1% increase in the proportion of exhaust gas in the admission fuel mixture, there is a 7°C reduction in flame temperature. This allowed Mazda to meet the United States Clean Air Act of 1970 in 1973, with a simple and inexpensive "thermal reactor", which was an enlarged chamber in the exhaust manifold. By decreasing the air-fuel ratio, unburned hydrocarbons (HC) in the exhaust would support combustion in the thermal reactor. Piston-engine cars required expensive catalytic converters to deal with both unburned hydrocarbons and NOx emissions. This inexpensive solution increased fuel consumption.


title: Wankel engine

text: Sales of Wankel engine cars suffered because of the oil crisis of 1973 raising the price of gasoline leading to lower sales. Toyota discovered that the injection of air into the exhaust port zone improved fuel economy reducing emissions. The best results were obtained with holes in the side plates, however, in the exhaust duct, there was no noticeable influence. The use of a three-stage catalyst, with air supplied in the middle, as for two-stroke piston engines, also proved beneficial in meeting emissions regulations.


title: Wankel engine

text: Mazda improved the fuel efficiency of the thermal reactor system by 40% with the RX-7 introduction in 1978. However, Mazda eventually shifted to the catalytic converter system. According to Curtiss-Wright research, the factor that controls the amount of unburned hydrocarbon in the exhaust is the rotor surface temperature, with higher temperatures producing less hydrocarbon. Curtiss-Wright widened the rotor, keeping the rest of engine's architecture unchanged, thus reducing friction losses and increasing displacement and power output. The limiting factor for this widening was mechanical, especially shaft deflection at high rotative speeds. Quenching is the dominant source of hydrocarbon at high speeds, and leakage at low speeds.


title: Wankel engine

text: Curtiss-Wright produced the RC2-60 engine, which was comparable to a V8 engine in performance and fuel consumption. Unlike NSU, Curtiss-Wright had solved the rotor sealing issue in 1966 with seals lasting .


title: Wankel engine

text: Automobile Wankel engines are capable of high-speed operation. It was discovered that an early opening of the intake port, longer intake ducts, and a greater rotor eccentricity can increase torque at lower rpm. The shape and positioning of the recess in the rotor, which forms most of the combustion chamber, influences emissions and fuel economy. The results in terms of fuel economy and exhaust emissions varies depending on the shape of the combustion recess which is determined by the placement of spark plugs per chamber of an individual engine.


title: Wankel engine

text: Mazda's RX-8 car with the Renesis engine met California State fuel economy requirements, including California's low emissions vehicle (LEV) standards. This was achieved by a number of innovations. The exhaust ports, which in earlier Mazda rotaries were located in the rotor housings, were moved to the sides of the combustion chamber. This solved the problem of the earlier ash buildup in the engine, and thermal distortion problems of the side intake and exhaust ports. A scraper seal was added to the rotor sides, and some ceramic parts were used in the engine. This approach allowed Mazda to eliminate overlap between intake and exhaust port openings, while simultaneously increasing the exhaust port area. The side port trapped the unburned fuel in the chamber, decreased the oil consumption, and improved the combustion stability in the low-speed and light load range. The HC emissions from the side exhaust port rotary engine are 35–50% less than those from the peripheral exhaust port Wankel engine, because of near zero intake and exhaust port opening overlap. Peripheral ported rotary engines have a better mean effective pressure, especially at high rpm and with a rectangular-shaped intake port. However, the RX-8 was not improved to meet Euro 5 emission regulations and was discontinued in 2012.


title: Wankel engine

text: Mazda is still continuing the development of the next-generation of Wankel engines. The company is researching engine laser ignition, which eliminates conventional spark plugs, direct fuel injection, sparkless HCCI ignition and SPCCI ignition. These lead to greater rotor eccentricity (equating to a longer stroke in a reciprocating engine), with improved elasticity and low revolutions-per-minute torque. Research by T. Kohno proved that installing a glow-plug in the combustion chamber improved part load and low revolutions per minute fuel economy by 7%. These innovations promise to improve fuel consumption and emissions.


title: Wankel engine

text: To improve fuel efficiency further, Mazda looked at using the Wankel as a range-extender in series-hybrid cars, announcing a prototype, the Mazda2 EV, for press evaluation in November 2013. This configuration improves fuel efficiency and emissions. As a further advantage, running a Wankel engine at a constant speed gives greater engine life. Keeping to a near constant, or narrow band, of revolutions eliminates, or vastly reduces, many of the disadvantages of the Wankel engine. Mazda stated they will be introducing in early 2023 an electric Wankel hybrid, the MX-30 R-EV, with the engine turning only a generator.


title: Wankel engine

text: In 2015 a new system to reduce emissions and increase fuel efficiency with Wankel Engines was developed by UK-based engineers AIE (UK) Ltd, following a licensing agreement to utilize patents from Norton rotary engine creator, David Garside. The CREEV system (Compound Rotary Engine for Electric Vehicles) uses a secondary rotor to extract energy from the exhaust, consuming unburnt exhaust products while expansion occurs in the secondary rotor stage, thus reducing overall emissions and fuel costs by recouping exhaust energy that would otherwise be lost. By expanding the exhaust gas to near atmospheric pressure, Garside also ensured the engine exhaust would remain cooler and quieter. AIE (UK) Ltd is now utilizing this patent to develop hybrid power units for automobiles and unmanned aerial vehicles.


title: Wankel engine

text: Traditional spark plugs need to be indented into the walls of the combustion chamber to enable the apex of the rotor to sweep past. As the rotor's apex seals pass over the spark plug hole, a small amount of compressed charge can be lost from the charge chamber to the exhaust chamber, entailing fuel in the exhaust, reducing efficiency, and resulting in higher emissions. These points have been overcome by using laser ignition, eliminating traditional spark plugs, and removing the narrow slit in the motor housing so the rotor apex seals can fully sweep with no loss of compression from adjacent chambers. This concept has a precedent in the glow plug used by Toyota (SAE paper 790435), and the SAE paper 930680, by D. Hixon et al., on 'Catalytic Glow Plugs in the JDTI Stratified Charge Rotary Engine'. The laser plug can fire through the narrow slit. Laser plugs can also fire deep into the combustion chamber using multiple lasers. So, a higher compression ratio is permitted. Direct fuel injection, to which the Wankel engine is suited, combined with laser ignition in single or multiple laser plugs, has been shown to enhance the motor even further reducing the disadvantages.


title: Wankel engine

text: Homogeneous charge compression ignition (HCCI) involves the use of a pre-mixed lean air-fuel mixture being compressed to the point of auto-ignition, so electronic spark ignition is eliminated. Gasoline engines combine homogeneous charge (HC) with spark ignition (SI), abbreviated as HCSI. Diesel engines combine stratified charge (SC) with compression ignition (CI), abbreviated as SCCI. HCCI engines achieve gasoline engine-like emissions with compression ignition engine-like efficiency, and low levels of nitrogen oxide emissions (NO) without a catalytic converter. However, unburned hydrocarbon and carbon monoxide emissions still require treatment to conform with automotive emission regulations.


title: Wankel engine

text: Mazda has undertaken research on HCCI ignition for its SkyActiv-R rotary engine project, using research from its SkyActiv Generation 2 program. A constraint of rotary engines is the need to locate the spark plug outside the combustion chamber to enable the rotor to sweep past. Mazda confirmed that the problem had been solved in the SkyActiv-R project. Rotaries generally have high compression ratios, making them particularly suitable for the use of HCCI.


title: Wankel engine

text: SPCCI incorporates spark and compression ignition. A spark is always used, to control exactly when combustion occurs. Depending on the load, it may be only spark ignition, other times SPCCI.


title: Wankel engine

text: The spark ignites a small pulse of richer mixture injected into the combustion chamber. A fireball is created, acting like an air piston, and increasing the pressure and temperature. Compression-ignition of the very lean mixture occurs, with a rapid and even and complete burn leading to a more powerful cycle. The compression-ignition aspect makes the lean burn possible, improving engine efficiency by up to 20–30%. It gives a rotary the ability to switch from the ideal, stoichiometric, 14.7:1 air-to-fuel mixture of a conventional gasoline-burning engine to the lean-burn mixture of over 29.4:1. The engine is in the lean-burn mode about 80% of running time. The combustion timing is controlled by the flame from the spark plug.


title: Wankel engine

text: According to Mazda, SPCCI combines the advantages of both petrol and diesel engines and gives high efficiency across a wide range of rpms and engine loads. Combined with a supercharger the compression ignition delivers an increase in torque of 20–30%.


title: Wankel engine

text: Research has been undertaken into rotary compression ignition engines and the burning of diesel heavy fuel using spark ignition. The basic design parameters of the Wankel engine preclude obtaining a compression ratio higher than 15:1 or 17:1 in a practical engine. The Rolls-Royce and Yanmar compression-ignition approach was to use a two-stage unit, with one rotor acting as compressor, while combustion takes place in the other. Conversion of a standard 294-cc-chamber spark-ignition unit to use heavy fuel was described in SAE paper 930682, by L. Louthan.


title: Wankel engine

text: Compression-ignition engine research is being undertaken by Pratt & Whitney Rocketdyne, which was commissioned by DARPA to develop a compression-ignition Wankel engine for use in a prototype VTOL flying car called the "Transformer". The engine, based on an earlier concept involving an unmanned aerial vehicle called "Endurocore", powered by a Wankel diesel. plans to utilize Wankel rotors of varying sizes on a shared eccentric shaft to increase efficiency. The engine is claimed to be a 'full-compression, full-expansion, compression-ignition-cycle engine'. An October 28, 2010 patent by Pratt & Whitney Rocketdyne, describes a Wankel engine superficially similar to Rolls-Royce's earlier prototype, that required an external air compressor to achieve high enough compression for compression-ignition-cycle combustion. The design differs from Rolls-Royce's compression-ignition rotary, mainly by proposing an injector both in the exhaust passage between the combustor rotor and expansion rotor stages, and an injector in the expansion rotor's expansion chamber, for 'afterburning'.


title: Wankel engine

text: The British company Rotron, which specializes in unmanned aerial vehicle (UAV) applications of Wankel engines, has designed and built a unit to operate on heavy fuel for NATO purposes. The engines uses spark ignition. The prime innovation is flame propagation, ensuring the flame burns smoothly across the whole combustion chamber. The fuel is pre-heated to 98 degrees Celsius before it is injected into the combustion chamber. Four spark plugs are utilized, aligned in two pairs. Two spark plugs ignite the fuel charge at the front of the rotor as it moves into the combustion section of the housing. As the rotor moves the fuel charge, the second two fire a fraction of a second behind the first pair of plugs, igniting near the rear of the rotor at the back of the fuel charge. The drive shaft is water-cooled which also has a cooling effect on the internals of the rotor. Cooling water also flows around the external of the engine through a gap in the housing, thus reducing the heat of the engine from outside and inside eliminating hot spots.


title: Wankel engine

text: As a hydrogen/air fuel mixture is quicker to ignite with a faster burning rate than gasoline, an important issue of hydrogen internal combustion engines is to prevent pre-ignition and backfire. In a rotary engine, each cycle of the Otto cycle occurs in different chambers. Importantly, the intake chamber is separated from the combustion chamber, keeping the air/fuel mixture away from localized hot spots. Wankel engines also do not have hot exhaust valves, which eases adapting them to hydrogen operation. Another problem concerns the hydrogenate attack on the lubricating film in reciprocating engines. In a Wankel engine, the problem of a hydrogenate attack is circumvented by using ceramic apex seals.


title: Wankel engine

text: In a prototype Wankel engine fitted to a Mazda RX-8 to research hydrogen operation, Wakayama et al. found that hydrogen operation improved thermal efficiency by 23% over petrol fuel operation. However, the exhaust gas behaviour significantly worsened due to high NOx emissions caused by lean combustion, which meant that the vehicle failed to comply with Japan's SULEV emissions standard. In order to comply with emissions regulations, a supplementary stoichiometric mode had to be used, which lowered the thermal efficiency of the engine.


title: Wankel engine

text: Wankel engines are considerably lighter and simpler, containing far fewer moving parts than piston engines of equivalent power output. Valves or complex valve trains are eliminated by using simple ports cut into the walls of the rotor housing. Since the rotor rides directly on a large bearing on the output shaft, there are no connecting rods and no crankshaft. The elimination of reciprocating mass, and the elimination of the most highly stressed and failure-prone parts of piston engines, gives the Wankel engine high reliability, a smoother flow of power, and a high power-to-weight ratio.


title: Wankel engine

text: The surface-to-volume ratio in the moving combustion chamber is so complex that a direct comparison cannot be made between a reciprocating piston engine and a Wankel engine. The flow velocity and the heat losses are quite different. Surface temperature characteristics are completely different; the film of oil in the Wankel engine acts as insulation. Engines with a higher compression ratio have a worse surface-to-volume ratio. When comparing the power-to-weight ratio, physical size, or physical weight to a similar power output piston engine, the Wankel is superior.


title: Wankel engine

text: A four-stroke cylinder produces a power stroke only every other rotation of the crankshaft, with three strokes being pumping losses. This doubles the real surface-to-volume ratio for the four-stroke reciprocating piston engine and the displacement increases. The Wankel, therefore, has higher volumetric efficiency and lower pumping losses through the absence of choking valves. Because of the quasi-overlap of the power strokes, which produces a smoother engine, the Wankel engine is very quick to react to power increases, giving a quick delivery of power when the demand arises, especially at higher RPMs. This difference is more pronounced when compared to four-cylinder reciprocating engines and less pronounced when compared to higher cylinder counts.


title: Wankel engine

text: In addition to the removal of internal reciprocating stresses by the complete removal of reciprocating internal parts typically found in a piston engine, the Wankel engine is constructed with an iron rotor within a housing made of aluminium, which has a greater coefficient of thermal expansion. This ensures that even a severely overheated Wankel engine cannot seize.


title: Wankel engine

text: From the combustion chamber shape and features, the fuel octane requirements of Wankel engines are lower than in reciprocating piston engines. The maximum road octane number requirements were 82 for a peripheral-intake port Wankel engine, and less than 70 for a side-inlet port engine. From the point of view of oil refiners this may be an advantage in fuel production costs.


title: Wankel engine

text: Due to a 50% longer stroke duration than a reciprocating four-cycle engine, there is more time to complete the combustion. This leads to greater suitability for direct fuel injection and stratified charge operation.


title: Wankel engine

text: Wankel rotary engines mainly suffer from poor thermodynamics caused by the Wankel engine's design with its huge surface area and poor combustion chamber shape. As an effect of this, the Wankel engine has a slow, and incomplete combustion, which results in high fuel consumption and bad exhaust gas behaviour.


title: Wankel engine

text: In a Wankel rotary engine, fuel combustion is slow, because the combustion chamber is long, thin, and moving. Flame travel occurs almost exclusively in the direction of rotor movement, adding to the poor quenching of a fuel/air mixture, being the main source of unburnt hydrocarbons at high engine speeds. The trailing side of the combustion chamber naturally produces a "squeeze stream" that prevents the flame from reaching the chamber trailing edge combined with the poor quenching of a fuel/air mixture. Direct fuel injection, in which fuel is injected towards the leading edge of the combustion chamber, can minimize the amount of unburnt fuel in the exhaust.


title: Wankel engine

text: Although many of the disadvantages are the subject of ongoing research, the current disadvantages of the Wankel engine in production are the following:


title: Wankel engine

text: Although in two dimensions the seal system of a Wankel looks to be even simpler than that of a corresponding multi-cylinder piston engine, in three dimensions the opposite is true. As well as the rotor apex seals evident in the conceptual diagram, the rotor must also seal against the chamber ends.


title: Wankel engine

text: Piston rings in reciprocating engines are not perfect seals; each has a gap to allow for expansion. The sealing at the apexes of the Wankel rotor is less critical because leakage is between adjacent chambers on adjacent strokes of the cycle, rather than to the mainshaft case. Although sealing has improved over the years, the less-than-effective sealing of the Wankel, which is mostly due to lack of lubrication, remains a factor reducing its efficiency.


title: Wankel engine

text: The trailing side of the rotary engine's combustion chamber develops a squeeze stream that pushes back the flame front. With the conventional one or two-spark-plug system and homogenous mixture, this squeeze stream prevents the flame from propagating to the combustion chamber's trailing side in the mid and high-engine speed ranges. Kawasaki dealt with that problem in its US patent ; Toyota obtained a 7% economy improvement by placing a glow-plug in the leading side, and using Reed-Valves in intake ducts. In two-stroke engines, metal reeds last about 15,000 km while carbon fiber, around 8,000 km. This poor combustion in the trailing side of the chamber is one of the reasons why there is more carbon monoxide and unburned hydrocarbons in a Wankel's exhaust stream. A side-port exhaust, as is used in the Mazda Renesis, avoids port overlap, one of the causes of this, because the unburned mixture cannot escape. The Mazda 26B avoided this problem through the use of a three spark-plug ignition system.


title: Wankel engine

text: The first rotary-engined car for sale was the The 1964 NSU Rotary Spider. Rotary engines were continuously fitted in cars until 2012 when Mazda discontinued the RX-8. Mazda has announced the introduction of a rotary-engined hybrid electric car, the MX-30 R-EV for a 2023 introduction.


title: Wankel engine

text: Mazda and NSU signed a study contract to develop the Wankel engine in 1961 and competed to bring the first Wankel-powered automobile to the market. Although Mazda produced an experimental rotary that year, NSU was the first with a rotary automobile for sale, the sporty NSU Spider in 1964; Mazda countered with a display of two- and four-rotor rotary engines at that year's Tokyo Motor Show. In 1967, NSU began production of a rotary-engined luxury car, the Ro 80. NSU had not produced reliable apex seals on the rotor, though, unlike Mazda and Curtiss-Wright. NSU had problems with apex seals' wear, poor shaft lubrication, and poor fuel economy, leading to frequent engine failures, not solved until 1972, which led to large warranty costs curtailing further NSU rotary engine development. This premature release of the new rotary engine gave a poor reputation for all makes, and even when these issues were solved in the last engines produced by NSU in the second half of the '70s, sales did not recover. Audi, after the takeover of NSU, built, in 1979, a new KKM 871 engine with side intake ports, a 750-cc chamber, at 6,500rpm, and 220Nm (162 ft-lb) at 3,500rpm. The engine was installed in an Audi 100 hull named "Audi 200", but was not mass-produced.


title: Wankel engine

text: Mazda claimed to have solved the apex seal problem, operating test engines at high speed for 300 hours without failure. After years of development, Mazda's first rotary engine car was the 1967 Cosmo 110S. The company followed with a number of Wankel ("rotary" in the company's terminology) vehicles, including a bus and a pickup truck. Customers often cited the cars' smoothness of operation. However, Mazda chose a method to comply with hydrocarbon emission standards that, while less expensive to produce, increased fuel consumption. Unfortunately for Mazda, this was introduced immediately prior to a sharp rise in fuel prices.


title: Wankel engine

text: Mazda later abandoned the rotary in most of their automotive designs, continuing to use the engine in their sports car range only. The company normally used two-rotor designs. A more advanced twin-turbo three-rotor engine was fitted in the 1990 Eunos Cosmo sports car. In 2003, Mazda introduced the Renesis engine fitted in the RX-8. The Renesis engine relocated the ports for exhaust from the periphery of the rotary housing to the sides, allowing for larger overall ports, better airflow, and further power gains. Some early Wankel engines also had side exhaust ports, the concept being abandoned because of carbon buildup in ports and the sides of the rotor. The Renesis engine solved the problem by using a keystone scraper side seal and approached the thermal distortion difficulties by adding some parts made of ceramics. The Renesis is capable of with improved fuel economy, reliability, and lower emissions than previous Mazda rotary engines, all from a nominal 1.3-L displacement, but this was not enough to meet more stringent emissions standards. Mazda ended production of their rotary engine in 2012 after the engine failed to meet the more stringent Euro 5 emission standards, leaving no automotive company selling a rotary-powered road vehicle. The company is continuing development of the next generation of Wankel engines, the SkyActiv-R. Mazda states that the SkyActiv-R solves the three key issues with previous rotary engines: fuel economy, emissions, and reliability. Mazda and Toyota announced they combined to produce a range-extending rotary engine for vehicles. Mazda will enter back into the rotary engine car market in March 2023, using the rotary as a generator in a MX-30 R-EV hybrid electric car.


title: Wankel engine

text: Citroën did much research, producing the M35 and GS Birotor cars, and the helicopter, using engines produced by Comotor, a joint venture by Citroën and NSU.


title: Wankel engine

text: American Motors Corporation (AMC), the smallest U.S. automaker, was so convinced "... that the rotary engine will play an important role as a powerplant for cars and trucks of the future ...", that the chairman, Roy D. Chapin Jr., signed an agreement in February 1973 after a year's negotiations, to build rotary engines for both passenger cars and military vehicles, as well as the right to sell any rotary engines it produced to other companies. AMC's president, William Luneburg, did not expect dramatic development through to 1980, but Gerald C. Meyers, AMC's vice president of the engineering product group, suggested that AMC should buy the engines from Curtiss-Wright before developing its own rotary engines, and predicted a total transition to rotary power by 1984.


title: Wankel engine

text: Plans called for the engine to be used in the AMC Pacer, but development was pushed back. American Motors designed the unique Pacer around the engine. By 1974, AMC had decided to purchase the General Motors (GM) rotary instead of building an engine in-house. Both GM and AMC confirmed the relationship would be beneficial in marketing the new engine, with AMC claiming that the GM rotary achieved good fuel economy. GM's engines had not reached production, though, when the Pacer was launched onto the market. The 1973 oil crisis played a part in frustrating the use of the rotary engine. Rising fuel prices and speculation about proposed US emission standards legislation also added to concerns.


title: Wankel engine

text: By 1974, GM R&D had not succeeded in producing a Wankel engine meeting both the emission requirements and good fuel economy, leading to a decision by the company to cancel the project. Because of that decision, the R&D team only partly released the results of its most recent research, which claimed to have solved the fuel-economy problem, as well as building reliable engines with a lifespan above . Those findings were not taken into account when the cancellation order was issued. The ending of GM's rotary project required AMC, who was to purchase the engine, to reconfigure the Pacer to house its AMC straight-6 engine driving the rear wheels.


title: Wankel engine

text: In 1978, AvtoVAZ designed an engine designated as VAZ-311 to be fitted into a VAZ-2101 car. In 1980, the company commenced delivery of the VAZ-411 twin-rotor Wankel engine in VAZ-2106 cars, with about 200 being manufactured. Most of the production went to the security services.


title: Wankel engine

text: Ford conducted research in rotary engines, resulting in patents granted: , 1974, a method for fabricating housings; 1974, side plates coating; , 1975, housing coating; , 1978: Housings alignment; , 1979, reed-valve assembly. In 1972, Henry Ford II stated that the rotary probably would not replace the piston in "my lifetime".


title: Wankel engine

text: In auto racing, Mazda has had success with two-rotor, three-rotor, and four-rotor cars. Private racers have also had success with stock and modified Mazda Wankel-engine cars.


title: Wankel engine

text: The Sigma MC74 powered by a Mazda 12A engine was the first engine and only team from outside Western Europe or the United States to finish the entire 24 hours of the 24 Hours of Le Mans race, in 1974. Yojiro Terada was the driver of the MC74. Mazda was the first team from outside Western Europe or the United States to win Le Mans outright. It was also the only non-piston engined car to win Le Mans, which the company accomplished in 1991 with their four-rotor 787B (—actual displacement, rated by FIA formula at ). In the C2 class, all participants had only the same amount of fuel at their disposal, besides the unregulated C1 Category 1. This category only allowed naturally aspirated engines. The Mazdas were classified as naturally aspirated to start with 830 kg weight, 170 kg less than the supercharged competitors. The cars under the Group C1 Category 1 regulations for 1991 were allowed to be another 80 kg lighter than the 787B. In addition, Group C1 Category 1 had only permitted 3,5 liter naturally aspirated engines and had no fuel quantity limits.


title: Wankel engine

text: Formula Mazda Racing features open-wheel race cars with Mazda Wankel engines, adaptable to both oval tracks and road courses, on several levels of competition. Since 1991, the professionally organized Star Mazda Series has been popular format for sponsors, spectators, and drivers. The engines are all built by one engine builder, certified to produce the prescribed power, and sealed to discourage tampering. They are in a relatively mild state of racing tune so they are reliable and can go years between motor rebuilds.


title: Wankel engine

text: The Malibu Grand Prix chain, similar in concept to commercial recreational kart racing tracks, operates several venues in the United States where a customer can purchase several laps around a track in a vehicle very similar to open wheel racing vehicles, but powered by a small Curtiss-Wright rotary engine.


title: Wankel engine

text: In engines having more than two rotors, or two-rotor race engines intended for high-rpm use, a multi-piece eccentric shaft may be used, allowing additional bearings between rotors. While this approach does increase the complexity of the eccentric shaft design, it has been used successfully in Mazda's production three-rotor 20B-REW engine, as well as many low-volume production race engines. The C-111-2 4 Rotor Mercedes-Benz eccentric shaft for the KE Serie 70, Type DB M950 KE409 is made in one piece. Mercedes-Benz used split bearings.


title: Wankel engine

text: Due to the compact size and the high power-to-weight ratio of a Wankel engine, it has been proposed for electric vehicles as range extenders to provide supplementary power when electric battery levels are low. There have been a number of concept cars incorporating a series hybrid powertrain arrangement. A Wankel engine used only as a generator has packaging, noise, vibration and weight distribution advantages when used in a vehicle, maximizing interior passenger and luggage space. The engine/generator may be at one end of the vehicle with the electric driving motors at the other, connected only by thin cables. Mitsueo Hitomi the global powertrain head of Mazda stated, "a rotary engine is ideal as a range extender because it is compact and powerful, while generating low-vibration".


title: Wankel engine

text: In 2010, Audi unveiled a prototype series-hybrid electric car, the A1 e-tron, that incorporated a small 250-cc Wankel engine, running at 5,000 rpm, which recharged the car's batteries as needed, and provided electricity directly to the electric driving motor. In 2010, FEV said that in their prototype electric version of the Fiat 500, a Wankel engine would be used as a range extender. In 2013, Valmet Automotive of Finland revealed a prototype car named the EVA, incorporating a Wankel powered series-hybrid powertrain car, utilizing an engine manufactured by the German company Wankel SuperTec. The UK company, Aixro Radial Engines, offers a range extender based on the 294cc-chamber go-kart engine.


title: Wankel engine

text: Mazda of Japan ceased production of direct-drive Wankel engines within their model range in 2012, leaving the motor industry worldwide with no production cars using the engine. The company is continuing development of the next generation of their Wankel engines, the SkyActiv-R. Mazda states that the SkyActiv-R solves the three key issues with previous rotary engines: fuel economy, emissions and reliability. Takashi Yamanouchi, the global CEO of Mazda said: "The rotary engine has very good dynamic performance, but it's not so good on economy when you accelerate and decelerate. However, with a range extender you can use a rotary engine at a constant 2,000rpm, at its most efficient. It's compact, too." No Wankel engine in this arrangement has yet been used in production vehicles or planes. However, in November 2013 Mazda announced to the motoring press a series-hybrid prototype car, the Mazda2 EV, using a Wankel engine as a range extender. The generator engine, located under the rear luggage floor, is a tiny, almost inaudible, single-rotor 330-cc unit, generating at 4,500rpm, and maintaining a continuous electric output of 20 kW. In October 2017, Mazda announced that the rotary engine would be utilised in a hybrid car with 2019/20 the targeted introduction dates.


title: Wankel engine

text: Mazda has undertaken research on Spark Controlled Compression Ignition (SPCCI) ignition on rotary engines stating that any new rotary engines will incorporate SPCCI. SPCCi incorporates spark and compression ignition combining the advantages of gasoline and diesel engines to achieve environmental, power, and fuel consumption goals.


title: Wankel engine

text: Mazda confirmed that a rotary-equipped range extended car would be launched. It will give full EV running with battery charging from the grid, with the engine performing the dual functions of a range-extender and battery charger when the battery charge is too low. When running on the engine, the electric motor is used to assist in acceleration and take off from stationary. Mazda announced a launch date of March 2023 for the MX-30 R-EV Range Extender car.


title: Wankel engine

text: The Japanese motoring press have reported that Toyota and Mazda will announce hybrid sports cars for 2026 launches.


title: Wankel engine

text: The small size and attractive power-to-weight ratio of the Wankel engine appealed to motorcycle manufacturers. The first Wankel-engined motorcycle was the 1960 'IFA/MZ KKM 175W' built by German motorcycle manufacturer MZ, licensed by NSU.


title: Wankel engine

text: In Britain, Norton Motorcycles developed a Wankel rotary engine for motorcycles, based on the Sachs air-cooled rotor Wankel that powered the DKW/Hercules W-2000 motorcycle. This two-rotor engine was included in the Commander and F1. Norton improved on the Sachs's air cooling, introducing a plenum chamber. Suzuki also made a production motorcycle powered by a Wankel engine, the RE-5, using ferroTiC alloy apex seals and an NSU rotor in a successful attempt to prolong the engine's life.


title: Wankel engine

text: In the early 1980s, using earlier work at BSA, Norton produced the air-cooled twin-rotor Classic, followed by the liquid-cooled Commander and the Interpol2 (a police version). Subsequent Norton Wankel bikes included the Norton F1, F1 Sports, RC588, Norton RCW588, and NRS588. Norton proposed a new 588-cc twin-rotor model called the "NRV588" and a 700-cc version called the "NRV700". A former mechanic at Norton, Brian Crighton, started developing his own rotary engined motorcycles line named "Roton", which won several Australian races.


title: Wankel engine

text: Despite successes in racing, no motorcycles powered by Wankel engines have been produced for sale to the general public for road use since 1992.


title: Wankel engine

text: In 1972, Yamaha introduced the RZ201 at the Tokyo Motor Show, a prototype with a Wankel engine, weighing 220 kg and producing from a twin-rotor 660-cc engine (US patent N3964448). In 1972, Kawasaki presented its two-rotor Kawasaki X99 rotary engine prototype (US patents N 3848574 &3991722). Both Yamaha and Kawasaki claimed to have solved the problems of poor fuel economy, high exhaust emissions, and poor engine longevity, in early Wankels, but neither prototype reached production.


title: Wankel engine

text: In 1974, Hercules produced W-2000 Wankel motorcycles, but low production numbers meant the project was unprofitable, and production ceased in 1977.


title: Wankel engine

text: From 1975 to 1976, Suzuki produced its RE5 single-rotor Wankel motorcycle. It was a complex design, with both liquid cooling and oil cooling, and multiple lubrication and carburetor systems. It worked well and was smooth, but being rather heavy, and having a modest power output of , it did not sell well.


title: Wankel engine

text: The two different design approaches, taken by Suzuki and BSA may usefully be compared. Even before Suzuki produced the RE5, in Birmingham BSA's research engineer David Garside, was developing a twin-rotor Wankel motorcycle. BSA's collapse put a halt to development, but Garside's machine eventually reached production as the Norton Classic.


title: Wankel engine

text: Wankel engines run very hot on the ignition and exhaust side of the engine's trochoid chamber, whereas the intake and compression parts are cooler. Suzuki opted for a complicated oil-cooling and water-cooling system, with Garside reasoning that provided the power did not exceed , air-cooling would suffice. Garside cooled the interior of the rotors with filtered ram-air. This very hot air was cooled in a plenum contained within the semi-monocoque frame and afterwards, once mixed with fuel, fed into the engine. This air was quite oily after running through the interior of the rotors, and thus was used to lubricate the rotor tips. The exhaust pipes become very hot, with Suzuki opting for a finned exhaust manifold, twin-skinned exhausted pipes with cooling grilles, heatproof pipe wrappings, and silencers with heat shields. Garside simply tucked the pipes out of harm's way under the engine, where heat would dissipate in the breeze of the vehicle's forward motion. Suzuki opted for complicated multi-stage carburation, whilst Garside choose simple carburetors. Suzuki had three lube systems, whilst Garside had a single total-loss oil injection system which was fed to both the main bearings and the intake manifolds. Suzuki chose a single rotor that was fairly smooth, but with rough patches at 4,000 rpm; Garside opted for a turbine-smooth twin-rotor motor. Suzuki mounted the massive rotor high in the frame, but Garside put his rotors as low as possible to lower the center of gravity of the motorcycle.


title: Wankel engine

text: Although it was said to handle well, the result was that the Suzuki was heavy, overcomplicated, expensive to manufacture, and at 62bhp short on power. Garside's design was simpler, smoother, lighter and, at , significantly more powerful.


title: Wankel engine

text: Dutch motorcycle importer and manufacturer Van Veen produced small quantities of a dual-rotor Wankel-engined OCR-1000 motorcycle between 1978 and 1980, using surplus Comotor engines. The engine of the OCR 1000, used a re-purposed engine originally intended for the Citroën GS Birotor car.


title: Wankel engine

text: In principle, rotary engines are ideal for light aircraft, being light, compact, almost vibrationless, and with a high power-to-weight ratio. Further aviation benefits of a rotary engine include:


title: Wankel engine

text: Unlike cars and motorcycles, a rotary aero-engine will be sufficiently warm before full power is asked of it because of the time taken for pre-flight checks. Also, the journey to the runway has minimum cooling, which further permits the engine to reach operating temperature for full power on take-off. A Wankel aero-engine spends most of its operational time at high power outputs, with little idling. This makes ideal use of peripheral ports. An advantage is that modular engines with more than two rotors are feasible, without increasing the frontal area. Should icing of any intake tracts be an issue, there is plenty of waste engine heat available to prevent icing.


title: Wankel engine

text: The first rotary engine aircraft was in the late 1960s being the experimental Lockheed Q-Star civilian version of the United States Army's reconnaissance QT-2, essentially a powered Schweizer sailplane. The plane was powered by a Curtiss-Wright RC2-60 Wankel rotary engine. The same engine model was also used in a Cessna Cardinal and a helicopter, as well as other airplanes. The French company Citroën developed a rotary powered helicopter in the 1970s.In Germany in the mid-1970s, a pusher ducted fan airplane powered by a modified NSU multi-rotor rotary engine was developed in both civilian and military versions, Fanliner and Fantrainer.


title: Wankel engine

text: At roughly the same time as the first experiments with full-scale aircraft powered with rotary engines, model aircraft-sized versions were pioneered by a combination of the well-known Japanese O.S. Engines firm and the then-extant German Graupner aeromodelling products firm, under license from NSU/Auto-Union. By 1968, the first prototype air-cooled, single-rotor glow plug-ignition, methanol-fueled 4.9 cm displacement OS/Graupner model Wankel engine was running, and was produced in at least two different versions from 1970 to the present day, solely by the O.S. firm after Graupner's demise in 2012.


title: Wankel engine

text: Aircraft rotary engines are increasingly being found in roles where the compact size, high power-to-weight ratio, and quiet operation are important, notably in drones and unmanned aerial vehicles. Many companies and hobbyists adapt Mazda rotary engines, taken from cars for aircraft use. Others, including Wankel GmbH itself, manufacture rotary engines dedicated to that purpose. One such use is the "Rotapower" engines in the Moller Skycar M400. Another example of purpose-built aircraft rotaries are Austro Engine's AE50R (certified) and AE75R (under development) both appr. 2 hp/kg.


title: Wankel engine

text: Rotary engines have been fitted in homebuilt experimental aircraft, such as the ARV Super2, a couple of which were powered by the British MidWest aero-engine. Most are Mazda 12A and 13B automobile engines, converted for aviation use. This is a very cost-effective alternative to certified aircraft engines, providing engines ranging from 100 to at a fraction of the cost of traditional piston engines. These conversions were initially in the early 1970s. With a number of these engines mounted on aircraft, as of 10 December 2006 the National Transportation Safety Board has only seven reports of incidents involving aircraft with Mazda engines, and none of these were a failure due to design or manufacturing flaws.


title: Wankel engine

text: Peter Garrison, a contributing editor for "Flying" magazine, has said that "in my opinion ... the most promising engine for aviation use is the Mazda rotary." Mazda rotaries have worked well when converted for use in homebuilt aircraft. However, the real challenge in aviation is to produce FAA-certified alternatives to the standard reciprocating engines that power most small general aviation aircraft. Mistral Engines, based in Switzerland, developed purpose-built rotaries for factory and retrofit installations on certified production aircraft. The G-190 and G-230-TS rotary engines were already flying in the experimental market, and Mistral Engines hoped for FAA and JAA certification by 2011. , G-300 rotary engine development ceased, with the company citing cash flow problems.


title: Wankel engine

text: Mistral claims to have overcome the challenges of fuel consumption inherent in the rotary, at least to the extent that the engines are demonstrating specific fuel consumption within a few points of reciprocating engines of similar displacement. While fuel burn is still marginally higher than traditional engines, it is outweighed by other beneficial factors.


title: Wankel engine

text: At the price of increased complication for a high-pressure diesel type injection system, fuel consumption in the same range as small pre-chamber automotive and industrial diesels has been demonstrated with Curtiss-Wright's stratified charge multi-fuel engines, while preserving Wankel rotary advantages Unlike a piston and overhead valve engine, there are no valves which can float at higher rpm causing loss of performance. The rotary is a more effective design at high revolutions with no reciprocating parts, far fewer moving parts, and no cylinder head.


title: Wankel engine

text: Since rotary engines operate at a relatively high rotational speed, at 6,000rpm of output shaft the rotor spins only at 2,000rmp. With relatively low torque, propeller-driven aircraft must use a propeller speed reduction unit to maintain propellers within the designed speed range. Experimental aircraft with Wankel engines use propeller speed reduction units, for example, the MidWest twin-rotor engine has a 2.95:1 reduction gearbox. The rotational shaft speed of a rotary engine is high compared to reciprocating piston designs. Only the eccentric shaft spins fast, while the rotors turn at exactly one-third of the shaft speed. If the shaft is spinning at 7,500rpm, the rotors are turning at a much slower 2,500rpm.


title: Wankel engine

text: Pratt & Whitney Rocketdyne has been commissioned by DARPA to develop a diesel rotary engine for use in a prototype VTOL flying car called the "Transformer". The engine, based on an earlier unmanned aerial vehicle Wankel diesel concept called "Endurocore".


title: Wankel engine

text: The sailplane manufacturer Schleicher uses an Austro Engines AE50R Wankel in its self-launching models ASK-21 Mi, ASH-26E, ASH-25 M/Mi, ASH-30 Mi, ASH-31 Mi, ASW-22 BLE, and ASG-32 Mi.


title: Wankel engine

text: In 2013, e-Go airplanes, based in Cambridge, United Kingdom, announced that its new single-seater canard aircraft, the winner of a design competition to meet the new UK single-seat deregulated category, will be powered by a rotary engine from Rotron Power, a specialist manufacturer of advanced rotary engines for unmanned aeronautical vehicle (UAV) applications. The first sale was in 2016. The aircraft is expected to deliver cruise speed from a rotary engine, with a fuel economy of using standard motor gasoline (MOGAS), developing .


title: Wankel engine

text: The DA36 E-Star, an aircraft designed by Siemens, Diamond Aircraft and EADS, employs a series hybrid powertrain with the propeller being turned by a Siemens electric motor. The aim is to reduce fuel consumption and emissions by up to 25%. An onboard Austro Engines rotary engine and generator provides the electricity. A propeller speed reduction unit is eliminated. The electric motor uses electricity stored in batteries, with the generator engine off, to take off and climb reducing sound emissions. The series-hybrid powertrain using the Wankel engine reduces the weight of the plane by 100 kg compared with its predecessor. The DA36 E-Star first flew in June 2013, making this the first-ever flight of a series-hybrid powertrain. Diamond Aircraft state that the technology using rotary engines is scalable to a 100-seat aircraft.


title: Wankel engine

text: Small Wankel engines are being found increasingly in other applications, such as go-karts, personal water craft, and auxiliary power units for aircraft. Kawasaki patented mixture-cooled rotary engine (US patent 3991722). Japanese diesel engine manufacturer Yanmar and Dolmar-Sachs of Germany had a rotary-engined chain saw (SAE paper 760642) and outboard boat engines, and the French Outils Wolf, made a lawnmower (Rotondor) powered by a Wankel rotary engine. To save on production costs, the rotor was in a horizontal position and there were no seals in the downside. The Graupner/O.S. 49-PI is a 5-cc Wankel engine for model airplane use, which has been in production essentially unchanged since 1970. Even with a large muffler, the entire package weighs only .


title: Wankel engine

text: The simplicity of the rotary engine makes it well-suited for mini, micro, and micro-mini engine designs. The Microelectromechanical systems (MEMS) Rotary Engine Lab at the University of California, Berkeley, has previously undertaken research towards the development of rotary engines of down to 1 mm in diameter, with displacements less than 0.1 cc. Materials include silicon and motive power includes compressed air. The goal of such research was to eventually develop an internal combustion engine with the ability to deliver 100 milliwatts of electrical power; with the engine itself serving as the rotor of the generator, with magnets built into the engine rotor itself. Development of the miniature rotary engine stopped at UC Berkeley at the end of the DARPA contract. Miniature rotary engines struggled to maintain compression due to sealing problems, similar to problems observed in the large-scale versions. In addition, miniature engines suffer from an adverse surface-to-volume ratio causing excess heat losses; the relatively large surface area of the combustion chamber walls transfers away what little heat is generated in the small combustion volume resulting in quenching and low efficiency.


title: Wankel engine

text: Ingersoll-Rand built the largest-ever rotary engine, with two rotors, which was available between 1975 and 1985, producing . A one-rotor version was available producing . The displacement per rotor was 41 liters, with each rotor being approximately one meter in diameter. The engine was derived from a previous, unsuccessful Curtiss-Wright design, which failed because of a well-known problem with all internal combustion engines: the fixed speed at which the flame front travels limits the distance combustion can travel from the point of ignition in a given time, thereby limiting the maximum size of the cylinder or rotor chamber which can be used. This problem was solved by limiting the engine speed to only 1200 rpm (400 kW per rotor) and the use of natural gas as fuel. That was particularly well chosen since one of the major uses of the engine was to drive compressors on natural gas pipelines. The engines used "homogeneous charge", and some ran for over 30,000 hours.


title: Wankel engine

text: John Deere acquired the Curtiss-Wright rotary division in February 1984, also making large multi-fuel prototypes, some with an 11-liter rotor for large vehicles. The developers attempted to solve the flame front issue (which hampered Ingersoll-Rand's homogeneous combustion) by stratifying the fuel in the combustion chamber. The technology was transferred to RPI in 1991.


title: Wankel engine

text: Yanmar of Japan produced some small, charge-cooled rotary engines for chainsaws and outboard engines. One of its products is the LDR (rotor recess in the leading edge of the combustion chamber) engine, which has better exhaust emissions profiles, and reed-valve controlled intake ports, which improve part-load and low rpm performance.


title: Wankel engine

text: In 1971 and 1972, Arctic Cat produced snowmobiles powered by Sachs KM 914 303-cc and KC-24 294-cc Wankel engines made in Germany.


title: Wankel engine

text: In the early 1970s, Outboard Marine Corporation sold snowmobiles under the Johnson and other brands, which were powered by OMC engines.


title: Wankel engine

text: Aixro of Germany produces and sells a go-kart engine, with a 294-cc-chamber charge-cooled rotor and liquid-cooled housings. Other makers are: Wankel AG, Cubewano, Rotron, and Precision Technology USA.


title: Wankel engine

text: The American M1A3 Abrams tank may use an rotary Diesel APU, developed by the TARDEC US Army lab. It has a high-power-density 330-cc rotary engine, modified to operate with various fuels such as standard military JP-8 jet fuel.


title: Wankel engine

text: In addition to use as an internal combustion engine, the basic Wankel design has also been used for gas compressors, and superchargers for internal combustion engines, but in these cases, although the design still offers advantages in reliability, the basic advantages of the Wankel in size and weight over the four-stroke internal combustion engine are irrelevant. In a design using a Wankel supercharger on a Wankel engine, the supercharger is twice the size of the engine.


title: Wankel engine

text: The Wankel design is used in the seat belt pre-tensioner system in some Mercedes-Benz and Volkswagen cars. When the deceleration sensors detect a potential crash, small explosive cartridges are triggered electrically, and the resulting pressurized gas feeds into tiny Wankel engines which rotate to take up the slack in the seat belt systems, anchoring the driver and passengers firmly in the seat before a collision.


title: Population density

text: Population density (in agriculture: standing stock or plant density) is a measurement of population per unit land area. It is mostly applied to humans, but sometimes to other living organisms too. It is a key geographical term. In simple terms, population density refers to the number of people living in an area per square kilometre, or other unit of land area.


title: Population density

text: Population density is population divided by total land area, sometimes including seas and oceans, as appropriate.


title: Population density

text: Low densities may cause an extinction vortex and further reduce fertility. This is called the Allee effect after the scientist who identified it. Examples of the causes of reduced fertility in low population densities are


title: Population density

text: Population density is the number of people per unit of area, usually transcribed as "per square kilometer" or square mile, and which may include or exclude, for example, areas of water or glaciers. Commonly this is calculated for a county, city, country, another territory or the entire world.


title: Population density

text: The world's population is around 8,000,000,000 and the Earth's total area (including land and water) is 510,000,000 km (197,000,000 sq. mi.). Therefore, from this very crude type of calculation, the worldwide human population density is approximately 7,800,000,000 ÷ 510,000,000 = 15.3/km (40 per sq. mi.). However, if only the Earth's land area of 150,000,000 km (58,000,000 sq. mi.) is taken into account, then human population density is 50/km (129 per sq. mi.). This includes all continental and island land area, including Antarctica. But if Antarctica is excluded, then population density rises to over 55 persons/km (over 142 per sq. mi.).


title: Population density

text: Several of the most densely populated territories in the world are city-states, microstates and urban dependencies. In fact, 95% of the world's population is concentrated on just 10% of the world's land. These territories have a relatively small area and a high urbanization level, with an economically specialized city population drawing also on rural resources outside the area, illustrating the difference between high population density and overpopulation.


title: Population density

text: Deserts have very limited potential for growing crops as there is not enough rain to support them. Thus, their population density is generally low. However, some cities in the Middle East, such as Dubai, have been increasing in population and infrastructure growth at a fast pace.Cities with high population densities are, by some, considered to be overpopulated, though this will depend on factors like quality of housing and infrastructure and access to resources. Very densely populated cities are mostly in Asia (particularly Southeast Asia); Africa's Lagos, Kinshasa, and Cairo; South America's Bogotá, Lima, and São Paulo; and Mexico City and Saint Petersburg also fall into this category.City population and especially area are, however, heavily dependent on the definition of "urban area" used: densities are almost invariably higher for the center only than when suburban settlements and intervening rural areas are included, as in the agglomeration or metropolitan area (the latter sometimes including neighboring cities).


title: Population density

text: In comparison, based on a world population of 7.8 billion, the world's inhabitants, if conceptualized as a loose crowd occupying just under 1 m (10 sq. ft) per person (cf. Jacobs Method), would occupy a space a little larger than Delaware's land area.


title: Population density

text: Although the arithmetic density is the most common way of measuring population density, several other methods have been developed to provide alternative measures of population density over a specific area.


title: Siobhan Finneran

text: Siobhán Margaret Finneran (born 27 April 1966) is a British actress. She made her screen debut in the 1987 independent film "Rita, Sue and Bob Too", and subsequently worked consistently in television drama including roles in "Coronation Street" (1989–1990), "Clocking Off" (2000–2002) and "The Amazing Mrs Pritchard" (2006). In 2005, Finneran originated the lead female role in the stage play "On the Shore of the Wide World" and was awarded the Manchester Evening News Theatre Award for Best Actress in a Leading Role. Also a comedy performer, Finneran appeared as Janice Garvey, a leading character in the first seven series of ITV sitcom "Benidorm" (2007–2015).


title: Siobhan Finneran

text: Later television roles include portraying a lawyer in the mini-series "Unforgiven" (2009), an embittered servant in the first three series of the costume drama "Downton Abbey" (2010–2012) and a recovering addict in "Happy Valley" (2014–present), for which she was nominated for the 2017 British Academy Television Award for Best Supporting Actress. Later film credits include Mrs Swift in the 2013 film release, "The Selfish Giant", which earned her a British Independent Film Award nomination. Finneran is also a prolific television documentary narrator.


title: Siobhan Finneran

text: Finneran was born in Oldham, Lancashire, on 27 April 1966 to Irish parents. As a child, Finneran was always drawn to the performing arts and was a fan of the celebrated English comedian Eric Morecambe, recalling that "as a little girl I wanted to be Eric Morecambe. Not to be like him but to actually be him".


title: Siobhan Finneran

text: After completing a theatre studies course she was in cast in her first major role, as Rita in the 1987 film "Rita, Sue and Bob Too". Kate Muir, chief film critic at UK newspaper "The Times", described the characters of Rita and Sue—two teenagers who both have a sexual affair with the older, married Bob (George Costigan)—"as raunchy, cheeky, unstoppable schoolgirls played with relish by Siobhan Finneran and Michelle Holmes. At its UK Premiere at the Brighton Film Festival, journalists were critical about the film's themes. Finneran, the youngest person there, challenged the critics who had enjoyed "Wish You Were Here" the previous night. She said it seemed the portrayal of underage sex in the 1950s was OK, “but because this is happening now, in 1987, it gives you the high ground to act like the bloody Vatican”.


title: Siobhan Finneran

text: Between August 1989 and March 1990, Finneran appeared as factory employee Josie Phillips, in the long running ITV1 soap opera "Coronation Street". The character of Josie is best remembered for her on-off employment, and difficult relationship, with her boss, Mike Baldwin.


title: Siobhan Finneran

text: Finneran continued to appear regularly on UK television, making guest appearances in numerous drama series including "Heartbeat" (1993, 1994, 2003), "Peak Practice" (1995), "Out of the Blue" (1996), "Where The Heart Is" (1997), "Hetty Wainthrop Investigates" (1998), Emmerdale as Heather Hutchinson (1998) and "The Cops" (1999). Finneran also established herself in comedic roles including episodes of "Josie" (a 1991 comedy series starring Josie Lawrence), "Cannon and Balls Playhouse" (1991) and as a regularly appearing cast member in ITV1's production of "The Russ Abbot Show" (1995–1996). Whilst having performed frequently in comedy, Finneran credits her performance as "a very damaged mother" in "Out of the Blue" in 1996 in triggering a shift towards more dramatic roles.


title: Siobhan Finneran

text: Between 2000 and 2002, Finneran appeared as Julie O'Neill in three series of the BBC1 drama series "Clocking Off". Subsequent roles in the early 21st century include the ITV1 Russell T Davies drama series "Bob & Rose" (2001), "Sparkhouse" (2002) –a modern re-telling of "Wuthering Heights" scripted by Sally Wainwright– and the two-part thriller "Passer By" (2004) starring James Nesbitt. In 2005, Finneran appeared as the female lead, Alice Holmes, in the original stage production of "On the Shore of the Wide World" at the Royal Exchange, Manchester. Finneran's performance earned her the Manchester Evening News Theatre Award for Best Actress in a Leading Role. In 2006, Finneran was cast as a series regular in "The Amazing Mrs Pritchard" (2006). Her character, Beverley Clarke is an established partner in a law firm who is inspired to launch a career in politics by her experience of the titular Ros Pritchard, and ultimately becomes an MP.


title: Siobhan Finneran

text: In 2007 Finneran appeared as Kelly in the British Independent film "Boy A". Also, in 2007, Finneran appeared as part of the original regular cast in the British sitcom "Benidorm" which details the experiences of holidaymakers and employees at the fictional Solana hotel in Benidorm, Spain. Finneran described her character Janice Garvey as "feisty, foul-mouthed and quite fantastic". Over the course of the series, Janice struggles to keep her family unit—comprising Janice's mother Madge (Sheila Reid), her husband Mick (Steve Pemberton) and their own children and grandchild—under control. A television correspondent at the "Sunday Mirror" described the character as a "fiercely protective lioness, humorous, straight-talking, and saucy" inclined to "let-it-all-hang-out" with a wardrobe comprising "skimpy, mutton-dressed-as-lamb outfits". Finneran found elements of the shoot embarrassing—including the requirement to be filmed in swimwear— and one scene which involved her character "snogging" a young barman played by an actor in his early twenties. In spite of the outlandish elements of the sitcom, Finneran notes that the cast "tried to find the truth in each character, to make them a real person – not a stereotype." In 2008, Finneran explained that as the series was filmed on location in Benidorm, her parents stepped in to help with childcare back home, with the children visiting during half-term.


title: Siobhan Finneran

text: Finneran would ultimately remain with the series, through to its 7th series, which aired in 2015. Discussing the enduring appeal of the series in 2013, Finneran stated that the series' fan base had become firmly established by the fourth series and that viewers were attracted to the "banter" and recognisable family dynamics that take viewers "to the extremes". She also felt that the contrasting summer setting and typical winter air date also provided a form of escapism for the UK audience. After discussing their intent to leave "Benidorm" during filming of the sixth series (2014), Pemberton and Finneran announced their joint departures ahead of the 7th series (2015). Both actors wanted to spend less time filming abroad, and neither wanted to leave on their own. Finneran found filming her last scenes "heartbreaking" noting she was in "a terrible state" upon bidding farewell to co-stars and crew with whom she had forged a close relationship.


title: Siobhan Finneran

text: Alongside her role in "Benidorm", Finneran continued to star in original drama series'. In 2008, she portrayed Sister Ruth, a Vatican nun drawn to investigate a priest who performs exorcisms, in five episodes of the supernatural thriller "Apparitions". In 2009, Finneran appeared as a main cast member in the three part ITV1 thriller "Unforgiven" as Izzie Ingram, a family lawyer who aids convicted murder Ruth Slater (Suranne Jones) track down her long lost sister. George Costigan, who appears in "Unforgiven" and first worked with Finneran in 1987 cited the mini-series as an illustration of Finneran's versatility, and justification of his appraisal of her as an acting "hero" and personal inspiration, stating that "she has no background in it and she just goes there. It's extraordinary. Those are the actors that electrify you." Also in 2009, Finneran appeared in episodes of "The Street", and "Blue Murder", and the straight-to-DVD soap opera spin-off "".


title: Siobhan Finneran

text: In 2010, it was announced that Finneran had been cast in "Downton Abbey", a period drama depicting the lives of the aristocratic Crawley family and their domestic servants. Upon its transmission, "Downton Abbey" received extensive critical acclaim, and strong viewing figures in both the UK and America.


title: Siobhan Finneran

text: During her time on the show, the "Downton Abbey" cast won the Screen Actors Guild Award for Outstanding Performance by an Ensemble in a Drama Series in 2012 (for series 2), and were nominated also in 2013 (for series 3). Finneran announced her departure in March 2013, ahead of the fourth series, explaining that she had been signed for only three series and did not wish to extend her contract, adding: "When I stop loving something, I stop doing it." Later that year, when asked by the "Radio Times" how her character's abrupt exit would be handled, Finneran retorted: "I'm hoping she's flung off the roof of the Abbey".


title: Siobhan Finneran

text: In 2013, Finneran starred in the second series of "The Syndicate" on BBC1, portraying Mandy, a hospital worker and domestic abuse victim who wins the national lottery with her colleagues. Finneran was attracted to the role because of the suspense of her character's storyline, and the challenge of keeping the abuse scenes as true-to-life as possible. Also in 2013, Finneran portrayed Mrs Swift in "The Selfish Giant" an independent film inspired by both Oscar Wilde's short story of the same name and screenwriter and director Clio Barnard's personal experiences of the socially fragmented northern English underclass. Finneran's character is a troubled yet loving mother, who she describes as "not quite the full shilling". In spite of the tough subject matter of the film Finneran enjoyed the filming process noting that she felt "safe and secure" in the hands of Barnard, who she felt to be a calmer director than any other she had worked with. For her portrayal, Finneran was nominated for the 2013 British Independent Film Award for Best Supporting Actress. In 2014, Finneran appeared in the French-Language film "Un Illustre Inconnu" ("Nobody from Nowhere").


title: Siobhan Finneran

text: Also in 2014, Finneran portrayed recovering heroin addict Clare in BBC One's "Happy Valley"—a crime drama that centres on the personal and occupational struggles faced by Clare's cohabitant sister, sergeant Catherine Cawood (Sarah Lancashire)—to general acclaim. Whilst eulogising the series' feminist credentials Gerald O'Donovan of "The Daily Telegraph" praised Finneran's "quietly compelling performance" and the character's "gritty wisdom" and stated viewers were unlikely to witness "a more believably crafted female character" that year. A second series aired in 2016, which gave more focus to Clare's backstory, interpersonal relationships and struggles with alcoholism. Reviewing an episode of the second series, Jack Seale of "The Guardian" described Finneran as "brilliant" in her depiction of both Clare's "jittery vulnerability" and portrayal of "a snarling addict who has relapsed". In spite of the series' subject matter, Finneran claimed that as an inept cook, she found having to peel carrots and act simultaneously the hardest part of filming.


title: Siobhan Finneran

text: By the time of "Happy Valley"s second series, Finneran had known Lancashire for over 30 years. Both their on-screen partnership and the depiction of middle-aged women in general in "Happy Valley" have been lauded as two of the series' most distinctive elements by television journalists and critics. Reflecting on the series' popularity, Finneran stated she felt viewers had taken the show to their hearts because the cast "reflected them" and "looked like real human beings with authentic emotions and flaws". "Radio Times" reviewer Alison Graham stated in 2016 that Finneran and Lancashire "should share every acting award going". Happy Valley won the British Academy Television Award for Best Drama Series in Both 2015 and 2017. Finneran was nominated in the Best Supporting Actress category in 2017. Though correctly predicting that she would not win the award, Ben Lawrence of "The Daily Telegraph" identified her as who he felt to be the deserving winner praising the "subtle, unfurling power" of her depiction. A third and final series of "Happy Valley" is expected to enter production, though not before Autumn 2018.


title: Siobhan Finneran

text: Between December 2014 and February 2015, Finneran appeared in the stage drama "3 Winters" at the Royal National Theatre in London. In Autumn 2015, Finneran played a supporting role in the three part supernatural drama serial "Midwinter of the Spirit".


title: Siobhan Finneran

text: In 2017, she portrayed real-life Detective Constable Christine Freeman in two-part drama "The Moorside", a depiction of the 2008 disappearance of Shannon Matthews told from the perspective of the local community. Upon reading the script, Finneran felt that "The Moorside" told a necessary story that illuminated truths that had been distorted by media coverage.


title: Siobhan Finneran

text: Finneran's next television role in 2017 was as Detective Chief Inspector Lauren Quigley, one of the protagonists in six-part ITV drama "The Loch", a crime mystery set on the banks of Loch Ness in the Scottish Highlands. Quigley is an ambitious English career detective drafted in to investigate a serial killer and acts as a foil to the other protagonist, working mother and local woman DC Annie Redford (Laura Fraser). Finneran was keen to star in the series after reading the first three scripts and finding both her character and the small community setting intriguing, in addition to the prospect of working with a former "Downton Abbey" director (Brian Kelly) and Laura Fraser, whose acting she had long admired. Finneran based herself in Glasgow during the filming shoot and enjoyed "the buzz, the architecture, the social life", describing the city as "one of my favourite places to ever work".


title: Siobhan Finneran

text: In 2019, she played Sally Newell in "The Widow" episode "Poteza". In the same year, Finneran also played Elaine Pickford in "A Confession", a TV dramatization of a true story about the murder of two young women in England and the unusual events resulting from the capture of their killer.


title: Siobhan Finneran

text: In 2020, Finneran reprised her role as Marilyn in the comedy series "The Other One", played Detective Sergeant Johanna Griffin in Netflix original mystery thriller "The Stranger", and narrated the ITV documentary series "Inside Britain's Food Factories".


title: Siobhan Finneran

text: From the late 1990s, Finneran began to consciously cut back her acting work to raise her two children as her husband, the actor Mark Jordon, (whom she married in August 1997) was regularly away from home filming as a series regular in "Heartbeat". In 2014, Finneran and Jordon divorced.


title: Medes

text: The Medes (Old Persian: ; Akkadian: , ; Ancient Greek: ; Latin: ) were an ancient Iranian people who spoke the Median language and who inhabited an area known as Media between western and northern Iran. Around the 11th century BC, they occupied the mountainous region of northwestern Iran and the northeastern and eastern region of Mesopotamia located in the region of Hamadan (Ecbatana). Their consolidation in Iran is believed to have occurred during the 8th century BC. In the 7th century BC, all of western Iran and some other territories were under Median rule, but their precise geographic extent remains unknown.


title: Medes

text: Although they are generally recognized as having an important place in the history of the ancient Near East, the Medes have left no written source to reconstruct their history, which is known only from foreign sources such as the Assyrians, Babylonians, Armenians and Greeks, as well as a few Iranian archaeological sites, which are believed to have been occupied by Medes. The accounts relating to the Medes reported by Herodotus have left the image of a powerful people, who would have formed an empire at the beginning of the 7th century BC that lasted until the 550s BC, played a determining role in the fall of the Assyrian Empire and competed with the powerful kingdoms of Lydia and Babylonia. However, a recent reassessment of contemporary sources from the Mede period has altered scholars' perceptions of the Median state. The state remains difficult to perceive in the documentation, which leaves many doubts about it, some specialists even suggesting that there never was a powerful Median kingdom. In any case, it appears that after the fall of the last Median king against Cyrus the Great of the Persian Empire, Media became an important province and prized by the empires which successively dominated it (Achaemenids, Seleucids, Parthians and Sasanids).


title: Medes

text: The six Median tribes resided in Media proper, the triangular area between Rhagae, Aspadana and Ecbatana. In present-day Iran, that is the area between Tehran, Isfahan and Hamadan, respectively. Of the Median tribes, the Magi resided in Rhagae, modern Tehran. They were of a sacred caste which ministered to the spiritual needs of the Medes. The Paretaceni tribe resided in and around Aspadana, modern Isfahan, the Arizanti lived in and around Kashan (Isfahan Province), and the Busae tribe lived in and around the future Median capital of Ecbatana, near modern Hamadan. The Struchates and the Budii lived in villages in the Median triangle.


title: Medes

text: The original source for their name and homeland is a directly transmitted Old Iranian geographical name which is attested as the Old Persian "Māda-" (). The meaning of this word is not precisely known. However, the linguist W. Skalmowski proposes a relation with the proto-Indo European word "med(h)-", meaning "central, suited in the middle", by referring to the Old Indic "madhya-" and Old Iranian "maidiia-" which both carry the same meaning. The Latin "medium", Greek "méso", Armenian "mej", and English "mid" are similarly derived from it.


title: Medes

text: Greek scholars during antiquity would base ethnological conclusions on Greek legends and the similarity of names. According to the "Histories" of Herodotus (440 BC):


title: Medes

text: In the Greek myth of Jason and the Argonauts, Medea is the daughter of King Aeëtes of Colchis and a paternal granddaughter of the sun-god Helios. Following her failed marriage to Jason while in Corinth, for one of several reasons depending on the version, she marries King Aegeus of Athens and bears a son Medus. After failing to make Aegeus kill his older son Theseus, she and her son fled to "Aria", where the Medes take their name from her, according to several Greek and later Roman accounts, including in Pausanias' "Description of Greece" (1st-century AD). According to other versions, such as in Strabo's "Geographica" (1st-century AD) and Justin's "Epitoma Historiarum Philippicarum" (2nd or 3rd century AD), she returned home to conquer neighboring lands with her husband Jason, one of which was named after her; while another version related by Diodorus Siculus in "Bibliotheca Historica" (1st-century BC) states that after being exiled she married an Asian king and bore Medus, who was greatly admired for his courage, after whom they took their name.


title: Medes

text: The discoveries of Median sites in Iran happened only after the 1960s. Prior to the 1960s, the search for Median archeological sources has mostly focused in an area known as the "Median triangle", defined roughly as the region bounded by Hamadān and Malāyer (in Hamadan Province) and Kangāvar (in Kermanshah Province). Three major sites from central western Iran in the Iron Age III period (i.e. 850–500 BC) are:


title: Medes

text: These sources have both similarities (in cultural characteristics) and differences (due to functional differences and diversity among the Median tribes). The architecture of these archaeological findings, which can probably be dated to the Median period, show a link between the tradition of columned audience halls often seen in the Achaemenid Empire (for example in Persepolis) and Safavid Iran (for example in Chehel Sotoun from the 17th century AD) and what is seen in Median architecture.


title: Medes

text: The materials found at Tepe Nush-i Jan, Godin Tepe, and other sites located in Media together with the Assyrian reliefs show the existence of urban settlements in Media in the first half of the 1st millennium BC which had functioned as centres for the production of handicrafts and also of an agricultural and cattle-breeding economy of a secondary type. For other historical documentation, the archaeological evidence, though rare, together with cuneiform records by Assyrian make it possible, regardless of Herodotus' accounts, to establish some of the early history of Medians.