An engine or motor is a machine designed to convert one form of energy into mechanical energy. Heat engines, like the internal combustion engine, burn a fuel to create heat, used to do work. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, clockwork motors in wind-up toys use elastic energy. In biological systems, molecular motors, like myosins in muscles, use chemical energy to create forces and motion; the word engine derives from Old French engin, from the Latin ingenium–the root of the word ingenious. Pre-industrial weapons of war, such as catapults and battering rams, were called siege engines, knowledge of how to construct them was treated as a military secret; the word gin, as in cotton gin, is short for engine. Most mechanical devices invented during the industrial revolution were described as engines—the steam engine being a notable example. However, the original steam engines, such as those by Thomas Savery, were not mechanical engines but pumps.
In this manner, a fire engine in its original form was a water pump, with the engine being transported to the fire by horses. In modern usage, the term engine describes devices, like steam engines and internal combustion engines, that burn or otherwise consume fuel to perform mechanical work by exerting a torque or linear force. Devices converting heat energy into motion are referred to as engines. Examples of engines which exert a torque include the familiar automobile gasoline and diesel engines, as well as turboshafts. Examples of engines which produce thrust include rockets; when the internal combustion engine was invented, the term motor was used to distinguish it from the steam engine—which was in wide use at the time, powering locomotives and other vehicles such as steam rollers. The term motor derives from the Latin verb moto which means to maintain motion, thus a motor is a device. Motor and engine are interchangeable in standard English. In some engineering jargons, the two words have different meanings, in which engine is a device that burns or otherwise consumes fuel, changing its chemical composition, a motor is a device driven by electricity, air, or hydraulic pressure, which does not change the chemical composition of its energy source.
However, rocketry uses the term rocket motor though they consume fuel. A heat engine may serve as a prime mover—a component that transforms the flow or changes in pressure of a fluid into mechanical energy. An automobile powered by an internal combustion engine may make use of various motors and pumps, but all such devices derive their power from the engine. Another way of looking at it is that a motor receives power from an external source, converts it into mechanical energy, while an engine creates power from pressure. Simple machines, such as the club and oar, are prehistoric. More complex engines using human power, animal power, water power, wind power and steam power date back to antiquity. Human power was focused by the use of simple engines, such as the capstan, windlass or treadmill, with ropes and block and tackle arrangements; these were used in cranes and aboard ships in Ancient Greece, as well as in mines, water pumps and siege engines in Ancient Rome. The writers of those times, including Vitruvius and Pliny the Elder, treat these engines as commonplace, so their invention may be more ancient.
By the 1st century AD, cattle and horses were used in mills, driving machines similar to those powered by humans in earlier times. According to Strabo, a water powered mill was built in Kaberia of the kingdom of Mithridates during the 1st century BC. Use of water wheels in mills spread throughout the Roman Empire over the next few centuries; some were quite complex, with aqueducts and sluices to maintain and channel the water, along with systems of gears, or toothed-wheels made of wood and metal to regulate the speed of rotation. More sophisticated small devices, such as the Antikythera Mechanism used complex trains of gears and dials to act as calendars or predict astronomical events. In a poem by Ausonius in the 4th century AD, he mentions a stone-cutting saw powered by water. Hero of Alexandria is credited with many such wind and steam powered machines in the 1st century AD, including the Aeolipile and the vending machine these machines were associated with worship, such as animated altars and automated temple doors.
Medieval Muslim engineers employed gears in mills and water-raising machines, used dams as a source of water power to provide additional power to watermills and water-raising machines. In the medieval Islamic world, such advances made it possible to mechanize many industrial tasks carried out by manual labour. In 1206, al-Jazari employed a crank-conrod system for two of his water-raising machines. A rudimentary steam turbine device was described by Taqi al-Din in 1551 and by Giovanni Branca in 1629. In the 13th century, the solid rocket motor was invented in China. Driven by gunpowder, this simplest form of internal combustion engine was unable to deliver sustained power, but was useful for propelling weaponry at high speeds towards enemies in battle and for fireworks. After invention, this innovation spread throughout Europe; the Watt steam engine was the first type of steam engine to make use of steam at a pressure just above atmospheric to drive the piston he
The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. All parts rotate in one direction, as opposed to the common reciprocating piston engine, which has pistons and changing direction 180 degrees. In contrast to the more common reciprocating piston designs, the Wankel engine delivers advantages of simplicity, compactness, high revolutions per minute, a high power-to-weight ratio; this is because there are three power pulses per rotor revolution. In a two-stroke piston engine there is one power pulse per crankshaft revolution, with one in two revolutions in a four-stroke piston engine. Although at the actual output shaft of a rotary engine, there is only one power pulse per revolution, since the output shaft spins three times as fast as the actual rotor, as can be seen in the animation below, it makes it equivalent to a two-stroke piston engine of the same displacement; this is why the displacement only measures one face of the rotor, since only one face is working for each output shaft revolution.
The engine is referred to as a rotary engine, although this name is applied to other different designs, including both pistoned and pistonless rotary engines. The four-stage cycle of intake, compression and exhaust occur each revolution at each of the three rotor tips moving inside the oval-like epitrochoid-shaped housing, enabling the three power pulses per rotor revolution; the rotor is similar in shape to a Reuleaux triangle with the sides somewhat flatter. The design was conceived by German engineer Felix Wankel. Wankel received his first patent for the engine in 1929, he began development in the early 1950s at NSU, completing a working prototype in 1957. NSU subsequently licensed the design to companies around the world, who have continually added improvements; the engines produced are of spark ignition, with compression ignition engines having only been built in research projects. The Wankel engine has the advantages of compact design and low weight over the most used internal combustion engine employing reciprocating pistons.
These advantages have given rotary engine applications in a variety of vehicles and devices, including: automobiles, racing cars, aircraft, go-karts, jet skis, snowmobiles and auxiliary power units. The power-to-weight ratio has reached over one horsepower per pound in certain engines. In 1951, NSU Motorenwerke AG in Germany began development of the engine, with two models being built; the first, the DKM motor, was developed by Felix Wankel. The second, the KKM motor, developed by Hanns Dieter Paschke, was adopted as the basis of the modern Wankel engine; the basis of the DKM type of motor was that both the rotor and the housing spun around on separate axes. The DKM motor reached higher revolutions per minute and was more balanced. However, the engine contained more parts; the KKM engine was simpler. The first working prototype, DKM 54, produced 21 hp and ran on February 1, 1957, at the NSU research and development department Versuchsabteilung TX; the KKM 57 was constructed by NSU engineer Hanns Dieter Paschke in 1957 without the knowledge of Felix Wankel, who remarked "you have turned my race horse into a plow mare".
In 1960, NSU, the firm that employed the two inventors, 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. Many manufacturers signed license agreements for development, attracted by the smoothness, quiet running, reliability emanating from the uncomplicated design. Amongst them were Alfa Romeo, American Motors Corporation, Citroën, General Motors, Mercedes-Benz, Porsche, Rolls-Royce 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. Citroën did much research, producing the M35, GS Birotor and RE-2 helicopter, using engines produced by Comotor, a joint venture of Citroën and NSU.
General Motors seemed to have concluded the Wankel engine was more expensive to build than an equivalent reciprocating engine. General Motors claimed to have solved the fuel economy issue, but failed in obtaining in a concomitant way to acceptable exhaust emissions. Mercedes-Benz fitted a Wankel engine in their C111 concept car. Deere & Company designed a version, 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. In 1961, the Soviet research organization of NATI, NAMI, VNIImotoprom commenced development creating experimental engines with different technologies. Soviet automobile manufacturer AvtoVAZ experimented in Wankel engine design without a license, introducing a limited number of engines in some cars. Despite much research and development throughout the world, only Mazda has produced Wankel engines in large quantities. 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. Suzuki made a production
In fluid dynamics, the drag coefficient is a dimensionless quantity, used to quantify the drag or resistance of an object in a fluid environment, such as air or water. It is used in the drag equation in which a lower drag coefficient indicates the object will have less aerodynamic or hydrodynamic drag; the drag coefficient is always associated with a particular surface area. The drag coefficient of any object comprises the effects of the two basic contributors to fluid dynamic drag: skin friction and form drag; the drag coefficient of a lifting airfoil or hydrofoil includes the effects of lift-induced drag. The drag coefficient of a complete structure such as an aircraft includes the effects of interference drag; the drag coefficient c d is defined as c d = 2 F d ρ u 2 A where: F d is the drag force, by definition the force component in the direction of the flow velocity, ρ is the mass density of the fluid, u is the flow speed of the object relative to the fluid, A is the reference area. The reference area depends on what type of drag coefficient is being measured.
For automobiles and many other objects, the reference area is the projected frontal area of the vehicle. This may not be the cross sectional area of the vehicle, depending on where the cross section is taken. For example, for a sphere A = π r 2. For airfoils, the reference area is the nominal wing area. Since this tends to be large compared to the frontal area, the resulting drag coefficients tend to be low, much lower than for a car with the same drag, frontal area, speed. Airships and some bodies of revolution use the volumetric drag coefficient, in which the reference area is the square of the cube root of the airship volume. Submerged streamlined bodies use the wetted surface area. Two objects having the same reference area moving at the same speed through a fluid will experience a drag force proportional to their respective drag coefficients. Coefficients for unstreamlined objects can be 1 or more, for streamlined objects much less, it has been demonstrated that drag coefficient c d is a function of Bejan number, Reynolds number and the ratio between wet area A w and front area A f: c d = A w A f B e R e L 2 where R e L is the Reynold Number related to fluid path length L.
The drag equation F d = 1 2 ρ u 2 c d A is a statement that the drag force on any object is proportional to the density of the fluid and proportional to the square of the relative flow speed between the object and the fluid. Cd is not a constant but varies as a function of flow speed, flow direction, object position, object size, fluid density and fluid viscosity. Speed, kinematic viscosity and a characteristic length scale of the object are incorporated into a dimensionless quantity called the Reynolds number R e. C d is thus a function of R e. In a compressible flow, the speed of sound is relevant, C d is a function of Mach number M a. For certain body shapes, the drag coefficient C d only depends on the Reynolds number R e, Mach number M a and the direction of the flow. For low Mach number M a, the drag coefficient is independent of Mach number; the variation with Reynolds number R e within a practical range of interest is small, while for cars at highway speed and aircraft at cruising speed, the incoming flow direction is more-or-less the same.
Therefore, the drag coefficient C d ca
The Mercedes-Benz E-Class is a range of executive cars manufactured by German automaker Mercedes-Benz in various engine and body configurations. Produced since 1953, the E-Class falls midrange in the Mercedes line-up, has been marketed worldwide across five generations. Before 1993, the E in Mercedes-Benz nomenclature was a suffix following a vehicle's model number which stood for Einspritzmotor, it began to appear in the early 1960s, when that feature began to be utilized broadly in the maker's product line, not just in its upper tier luxury and sporting models. By the launch of the facelifted W124 in 1993 fuel-injection was ubiquitous in Mercedes engines, the E was adopted as a prefix and the model line referred to as the E-Class. All generations of the E-Class have offered either rear-wheel drive or Mercedes' 4Matic four-wheel drive system; the E-Class is Mercedes-Benz' best-selling model, with more than 13 million sold by 2015. The first E-Class series was available as four-door sedan, five-door station wagon, 2 door coupe and 2 door convertible.
From 1997 to 2009, the equivalent coupe and convertible were sold under the Mercedes-Benz CLK-Class nameplate. With the latest incarnation of the E-Class released for the 2017 model year, all body styles share the same W213 platform. Due to the E-Class's size and durability, it has filled many market segments, from personal cars to serving as taxis in European countries, as well special-purpose vehicles from the factory; the first modern midsize Mercedes was the W120'Ponton' 180 of 1953 and was produced till 1962. Sharing its engineering with the R121 190 SL of 1955, the Ponton was a stylish sedan with a four-cylinder engine. A larger-engined W121 190 appeared in 1958. Mercedes added tailfins to both the big S-Class and the new W110'Fintail' 190 of 1962. In the 1965 230 model a Straight-6 engine appeared for the first time, the four cylinder engine grew in displacement; the midsize Mercedes was redesigned in 1968 as the W114/W115'Stroke-8'. This time, the 6-cylinder models were most prevalent, with the W115 line making up the bottom of the company's offerings with four – and five-cylinder power.
Diesel engines joined the line-up. The popular W123 became a best-seller on its launch in 1976. In diesel powered 200D and 240D guises, the cars enhanced the company's reputation for product quality. Over 2.6 million were produced until the end of production in 1986. Saloon/Sedan, Coupé and Estate body configurations were offered; the W124 was introduced several new standards for a mid-size Mercedes. It was the third car to inherit the company's new design theme since the late 1970s, following the flagship W126 and compact W201. Similar to its predecessors, the W124 offered a coupé and estate body styles. A new convertible was available, making it the first mid-size Mercedes convertible; the "E-Class" name first appeared in with the facelifted W124 in 1993 for the model year 1994. The diesel versions continued to be the fuel economy option over the four and six-cylinder gasoline engines, the gasoline V8 engines increased gasoline power outputs further. Four-cylinder gasoline models were not marketed in the United States.
The V8 powered sedans/saloons were named 400 E/500 E from 1992–1993, E 420/E 500 after 1993. The 3.0-litre cars were re-badged to E 320 with the new 3.2-litre M104 engines and naming rationalization of 1994. For the diesel models the name change was less elegant, with the 250 D becoming the E 250 Diesel for example. Sedan, Coupé, Convertible and Estate body configurations were offered; the W210 E-Class, launched in 1995, brought the line into the upper end of the mid-size luxury market. In September 1999 the W210 E-class was facelifted; this included visual and quality improvements over the earlier versions. The Mercedes-Benz E-Class was Motor Trend's Import Car of the Year for 1996. While the W210 sedan was replaced by the W211 in 2002, the wagon version continued to be sold until March 2003 when the W211 wagon replaced the W210 wagon. Launched in 2002, the W211 E-Class was another evolution of the previous model; the W211-based W219 CLS-Class sedan was introduced as a niche model in 2005 to attract a younger demographic.
The W211 E-Class was facelifted in June 2006 for the 2007 model year to address quality and technical issues raised by earlier models, Sensotronic was dropped, while Pre-Safe was made standard. The largest factory built engine in the E-class range is the E500 which had its engine size increased from 5 litres to 5.5 litres in 2006 along with the facelift. There is an AMG model badged E63 AMG and other tuning house installations. In 2007 the diesel version of the E-Class was rebadged from CDI to Bluetec. While in some of the other Mercedes-Benz diesels urea injection was added, in the W211 E-Class the Bluetec name was only adopted to prevent confusion in the diesel lineup; the W212 replaced the W211 in 2009. Official photos of the W212 were leaked on the internet on 9 De
Fuel injection is the introduction of fuel in an internal combustion engine, most automotive engines, by the means of an injector. All diesel engines use fuel injection by design. Petrol engines can use gasoline direct injection, where the fuel is directly delivered into the combustion chamber, or indirect injection where the fuel is mixed with air before the intake stroke. On petrol engines, fuel injection replaced carburetors from the 1980s onward; the primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake air accelerated through a Venturi tube to draw the fuel into the airstream. The functional objectives for fuel injection systems can vary. All share the central task of supplying fuel to the combustion process, but it is a design decision how a particular system is optimized. There are several competing objectives such as: Power output Fuel efficiency Emissions performance Running on alternative fuels Reliability Driveability and smooth operation Initial cost Maintenance cost Diagnostic capability Range of environmental operation Engine tuningModern digital electronic fuel injection systems optimize these competing objectives more and than earlier fuel delivery systems.
Carburetors have the potential to atomize fuel better. Benefits of fuel injection include smoother and more consistent transient throttle response, such as during quick throttle transitions, easier cold starting, more accurate adjustment to account for extremes of ambient temperatures and changes in air pressure, more stable idling, decreased maintenance needs, better fuel efficiency. Fuel injection dispenses with the need for a separate mechanical choke, which on carburetor-equipped vehicles must be adjusted as the engine warms up to normal temperature. Furthermore, on spark ignition engines, fuel injection has the advantage of being able to facilitate stratified combustion which have not been possible with carburetors, it is only with the advent of multi-point fuel injection certain engine configurations such as inline five cylinder gasoline engines have become more feasible for mass production, as traditional carburetor arrangement with single or twin carburetors could not provide fuel distribution between cylinders, unless a more complicated individual carburetor per cylinder is used.
Fuel injection systems are able to operate regardless of orientation, whereas carburetors with floats are not able to operate upside down or in microgravity, such as encountered on airplanes. Fuel injection increases engine fuel efficiency. With the improved cylinder-to-cylinder fuel distribution of multi-point fuel injection, less fuel is needed for the same power output. Exhaust emissions are cleaner because the more precise and accurate fuel metering reduces the concentration of toxic combustion byproducts leaving the engine; the more consistent and predictable composition of the exhaust makes emissions control devices such as catalytic converters more effective and easier to design. Herbert Akroyd Stuart developed the first device with a design similar to modern fuel injection, using a'jerk pump' to meter out fuel oil at high pressure to an injector; this system was used on the hot-bulb engine and was adapted and improved by Bosch and Clessie Cummins for use on diesel engines. Fuel injection was in widespread commercial use in diesel engines by the mid-1920s.
An early use of indirect gasoline injection dates back to 1902, when French aviation engineer Leon Levavasseur installed it on his pioneering Antoinette 8V aircraft powerplant, the first V8 engine of any type produced in any quantity. Another early use of gasoline direct injection was on the Hesselman engine invented by Swedish engineer Jonas Hesselman in 1925. Hesselman engines use the ultra lean-burn principle, they are started on gasoline and switched to diesel or kerosene. Direct fuel injection was used in notable World War II aero-engines such as the Junkers Jumo 210, the Daimler-Benz DB 601, the BMW 801, the Shvetsov ASh-82FN. German direct injection petrol engines used injection systems developed by Bosch from their diesel injection systems. Versions of the Rolls-Royce Merlin and Wright R-3350 used single point fuel injection, at the time called "Pressure Carburettor". Due to the wartime relationship between Germany and Japan, Mitsubishi had two radial aircraft engines using fuel injection, the Mitsubishi Kinsei and the Mitsubishi Kasei.
Alfa Romeo tested one of the first electronic injection systems in Alfa Romeo 6C 2500 with "Ala spessa" body in 1940 Mille Miglia. The engine had six electrically operated injectors and were fed by a semi-high-pressure circulating fuel pump system. All diesel engines have fuel injected into the combustion chamber. See Diesel engine; the invention of mechanical injection for gasoline-fueled aviation engines was by the French inventor of the V8 engine configuration, Leon Levavasseur in 1902. Levavasseur designed the original Antoinette firm's series of V-form aircraft engines, starting with the Antoinette 8V to be used by the aircraft the Antoinette firm built that Levavasseur designed, flown from 1906 to the firm's demise in 1910, with t
A transverse engine is an engine mounted in a vehicle so that the engine's crankshaft axis is perpendicular to the direction of travel. Many modern front wheel drive vehicles use this engine mounting configuration. Most rear wheel drive vehicles use a longitudinal engine configuration, where the engine's crankshaft axis is parallel with the direction of travel, except for some rear-mid engine vehicles, which use a transverse engine and transaxle mounted in the rear instead of the front. Despite being used in light vehicles, it is not restricted to light vehicles and has been used on armored vehicles to save interior space; the Critchley light car, made by the Daimler Motor Company in 1899, had a transverse engine with belt drive to the rear axle. A 1911 front-wheel drive car had a transverse engine with a clutch at each end, driving the front wheels directly; the first successful transverse-engine cars were the two-cylinder DKW "Front" series of cars, which first appeared in 1931. During WWII transverse engines were developed for armored vehicles, with the Soviet T-44 and T-54/T-55 being equipped with transverse engines to save space in the hull.
The T-54/55 became the most produced tank in history. After the Second World War, SAAB used the configuration in their first model, the Saab 92, in 1947; the arrangement was used for Borgward's Goliath and Hansa brand cars and in a few other German cars. However, it was with Alec Issigonis's Mini, introduced by the British Motor Corporation in 1959, that the design gained acclaim. Issigonis incorporated the car's gearbox into the engine's sump, producing a drivetrain unit narrow enough to install transversely in a car only four feet wide. While previous DKW and Saab cars used small two-stroke air-cooled engines with poor refinement and performance the gearbox-in-sump arrangement meant that an 848cc four-cylinder water-cooled engine could be fitted to the Mini, providing strong performance for a car of its size. Coupled to the much greater interior space afforded by the layout this made the Mini a genuine alternative to the conventional small family car; this design reached its ultimate extent starting with Dante Giacosa's elaboration of it for Fiat.
He connected the engine to its gearbox by a shaft and set the differential off-center so that it could be connected to the gearbox more easily. The axleshafts from the differential to the wheels therefore differed in length, which would have made the car's steering asymmetrical were it not for their torsional stiffness being made the same. Giacosa's lay-out was first used in the Autobianchi Primula in 1964 and in the wide-selling Fiat 128. With the gearbox mounted separately to the engine these cars were by neccesity larger than the Mini but this proved to be no disadvantage; the Giacosa lay-out provided superior refinement, easier repair and was better-suited to adopting five-speed transmissions than the original Issigonis in-sump design. Now most small and small/medium-sized cars built throughout the world use this arrangement; the Lamborghini Miura used a transverse, mid-mounted 4.0 litre V12, a configuration, unheard of in 1965, although now more common The Land Rover LR2 Freelander, along with all Volvo models from 1998 on, employ a transversely-mounted engine in order to increase passenger space inside the vehicle.
This has allowed for improved safety in a frontal impact, due to more front to back engine compartment space being created. The result is a larger front crumple zone. Transverse engines have been used in buses. In the United States they were offered in the early 1930s by Twin Coach and used with limited success in Dwight Austin's Pickwick Nite-Coach. Transverse bus engines first appeared in the Yellow Coach 719, using Dwight Austin's V-drive, they were used in the British Leyland Atlantean and in many transit buses and nearly all modern double decker buses. They have been used by Scania, MAN, Volvo and Renault's bus divisions. Engines may be placed in two main positions within the motor car: Front-engine transversely-mounted / Front-wheel drive Rear mid-engine transversely-mounted / Rear-wheel drive Space allowed for engines within the front wheel wells is limited to the following: Single cylinder Inline-two Inline-three Inline-four Inline-five V4 V6 The description of the orientation of V-twin and flat-twin motorcycle engines sometimes differs from the convention as stated above.
Motorcycles with a V-twin engine mounted with its crankshaft mounted in line with the frame, e.g. the AJS S3 V-twin, Indian 841, Victoria Bergmeister, Honda CX series and several Moto Guzzis since the 1960s, are said to have "transverse" engines, while motorcycles with a V-twin mounted with its crankshaft mounted perpendicular to the frame, e.g. most Ducatis since the 1970s and most Harley-Davidsons, are said to have "longitudinal" engines. This convention uses the longest horizontal dimension of the engine as its axis instead of the line of the crankshaft. Clarke, Massimo. Modern Motorcycle Technology: How Every Part of Your Motorcycle Works. Minneapolis, MN USA: MotorBooks International. P. 44. ISBN 978-0-7603-3819-3. Retrieved 2013-05-31. Moto Guzzi's transverse V-twins are unique among motorcycles, while Ducati, in keeping with the classical school, uses a longitudinal V, meaning the axis of rotation of the crankshaft is transverse to the frame. Douglas-Scott-Montagu, Edward John Barrington & Burgess-Wise, David.
Daimler Century: The ful
Rear mid-engine, rear-wheel-drive layout
In automotive design, a RMR or Rear Mid-engine, rear-wheel-drive layout is one in which the rear wheels are driven by an engine placed just in front of them, behind the passenger compartment. In contrast to the rear-engined RR layout, the center of mass of the engine is in front of the rear axle; this layout is chosen for its low moment of inertia and favorable weight distribution. The layout has a tendency toward being heavier in the rear than the front, which allows for best balance to be achieved under braking. However, since there is little weight over the front wheels, under acceleration, the front of the car is prone to lift and cause understeer. Most rear-engine layouts have been used in smaller vehicles, because the weight of the engine at the rear has an adverse effect on a larger car's handling, making it'tail-heavy', it is felt. The mid-engined layout uses up central space, making it impractical for any but two-seater sports cars. However, some microvans use this layout, with a low engine beneath the loading area.
This makes it possible to move the driver right to the front of the vehicle, thus increasing the loading area at the expense of reduced load depth. In modern racing cars, RMR is the usual configuration and is synonymous with "mid engine". Due to its weight distribution and resulting favorable vehicle dynamics, this layout is employed in open-wheel Formula racing cars as well as purpose-built sports racing cars; this configuration was common in small engined 1950s microcars, in which the engines did not take up much space. Because of successes in racing, the RMR platform has been popular for road-going sports cars despite the inherent challenges of design and lack of cargo space; the similar mid-engine, four-wheel-drive layout gives many of the same advantages and is used when extra traction is desired, such as in some supercars and in the Group B rally cars. The 1900 NW Rennzweier was one of the first race cars with rear-wheel-drive layout. Other known historical examples include the 1923 Benz Tropfenwagen.
It was based on an earlier design named the Rumpler Tropfenwagen in 1921 made by Edmund von Rumpler, an Austrian engineer working at Daimler. The Benz Tropfenwagen was designed by Ferdinand Porsche along with Hans Nibel, it raced in 1923 and 1924 and was most successful in the Italian Grand Prix in Monza where it stood fourth. Ferdinand Porsche used mid-engine design concept towards the Auto Union Grand Prix cars of the 1930s which became the first winning RMR racers, they were decades before their time, although MR Miller Specials raced a few times at Indianapolis between 1939 and 1947. In 1953 Porsche premiered the tiny and altogether new RMR 550 Spyder and in a year it was notoriously winning in the smaller sports and endurance race car classes against much larger cars—a sign of greater things to come; the 718 followed in 1958. But it was not until the late 1950s that RMR reappeared in Grand Prix races in the form of the Cooper-Climax, soon followed by cars from BRM and Lotus. Ferrari and Porsche soon made.
The mid-engined layout was brought back to Indianapolis in 1961 by the Cooper Car Company with Jack Brabham running as high as third and finishing ninth. Cooper did not return, but from 1963 on British built mid-engined cars from constructors like Brabham and Lola competed and in 1965 Lotus won Indy with their Type 38. Rear mid-engines were used in microcars like the Isetta or the Zündapp Janus; the first rear mid-engined road car after WW II was the 1962 Bonnet / Matra Djet, which used the 1108cc Renault Sierra engine, mated to the transaxle from the FWD Renault Estafette van. Nearly 1700 were built until 1967; this was followed by the first De Tomaso, the Vallelunga, which mated a tuned Ford Cortina 1500 Kent engine to a VW transaxle with Hewland gearsets. Introduced at Turin in 1963, 58 were built 1964-68. A similar car was the Renault-engined Lotus Europa, built from 1966–1975. In 1966, the Lamborghini Miura was the first high performance mid-engine, rear-wheel-drive roadcar; the concept behind the Miura was that of putting on the road a grand tourer featuring state-of-the-art racing-car technology of the time.
This represented an innovative sportscar at a time when all of its competitors, from Ferraris to Aston Martins, were traditional front-engined, rear wheel drive grand tourers. The Pontiac Fiero was a mid-engined sports car, built by the Pontiac division of General Motors from 1984 to 1988; the Fiero was the first two-seater Pontiac since the 1926 to 1938 coupes, the first and only mass-produced mid-engine sports car by a U. S. manufacturer. Engine and driveline layout considerations