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45-508: The 1.8-liter engine option had a single camshaft and three valves per cylinder, producing 97 PS (71 kW), while the two-litre option had twin camshafts and four valves per cylinder, with a max output of 140 PS (103 kW). Both engines could also be found in the Capella/626 range and other MA platform cars, although the two-litre was tuned for more torque in this application, and both were fuel injected. In February 1990

90-456: A DOHC configuration gradually increased after World War II, beginning with sports cars. Iconic DOHC engines of this period include the 1948–1959 Lagonda straight-six engine , the 1949–1992 Jaguar XK straight-six engine and the 1954–1994 Alfa Romeo Twin Cam inline-four engine. The 1966-2000 Fiat Twin Cam inline-four engine was one of the first DOHC engines to use a toothed timing belt instead of

135-660: A cigarette lighter - they were available as a cost option. A pull-out drawer located underneath the passenger seat replaced a traditional glove compartment. There were two equipment levels, Type A and Type B. Both were well equipped, but the Type B added extras such as leather interior. When Mazda launched the Eunos dealership channel in Japan for 1990, launched on 1 November 1989, the Persona became available with Eunos 300 badging. Unlike

180-557: A flat engine. A V engine or flat engine requires four camshafts to function as a DOHC engine, since having two camshafts in total would result in only a single camshaft per cylinder bank for these engine layouts. Some V engines with four camshafts have been marketed as "quad-cam" engines, however technically "quad-cam" would require four camshafts per cylinder bank (i.e. eight camshafts in total), therefore these engines are merely dual overhead camshaft engines. Many DOHC engines have four valves per cylinder. The camshaft usually operates

225-608: A fully enclosed-drivetrain), the American Liberty L-12 V12 engine, which closely followed the later Mercedes D.IIIa design's partly-exposed SOHC valvetrain design; and the Max Friz -designed; German BMW IIIa straight-six engine. The DOHC Napier Lion W12 engine was built in Great Britain beginning in 1918. Most of these engines used a shaft to transfer drive from the crankshaft up to the camshaft at

270-530: A limited edition "Persona Couture" arrived, only available in Silver Stone Metallic paint. It was fully equipped, with air condition and ABS brakes over the Type B, and only available with the larger engine in combination with the automatic transmission. It sold for ten percent more than a 2000 Type B. The Persona underwent a minor change in March 1990, with new body colors and more equipment, such as

315-465: A lower grade of fuel. Harry Ricardo was prominent in developing combustion chambers for diesel engines, the best known being the Ricardo Comet . In a continuous flow system, for example a jet engine combustor , the pressure is controlled and the combustion creates an increase in volume. The combustion chamber in gas turbines and jet engines (including ramjets and scramjets ) is called

360-594: A manual transmission and 145 PS (107 kW) with the automatic. To further its sporting pretensions it also came equipped with a front strut bar and a lower tie bar at the rear. Along with the Eunos Roadster ( Mazda MX-5 Miata ). the Eunos 100 ( Mazda Familia Astina ), and the 1990 Eunos Cosmo, these formed the initial Eunos brand lineup. The Eunos 300 was a stop-gap solution until the January 1992 launch of

405-457: A power seat and optional ABS brakes . The 12-valve 1.8 was replaced by a twin-cam 16-valve unit which had already been seen in the Eunos 300, producing 115 PS (85 kW). Unlike the case of the Eunos, however, the 2-liter FE DOHC engine remained unchanged. Production came to a halt in December 1991, although the car remained on sale for another three months. Mazda placed much emphasis on

450-406: A timing chain. In the 1980s, the need for increased performance while reducing fuel consumption and exhaust emissions saw increasing use of DOHC engines in mainstream vehicles, beginning with Japanese manufacturers. By the mid-2000s, most automotive engines used a DOHC layout. Combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix

495-425: Is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. In an internal combustion engine , the pressure caused by the burning air/fuel mixture applies direct force to part of the engine (e.g. for a piston engine, the force is applied to the top of the piston), which converts the gas pressure into mechanical energy (often in

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540-531: Is possible. The first known automotive application of timing belts to drive overhead camshafts was the 1953 Devin-Panhard racing specials built for the SCCA H-modified racing series in the United States. These engines were based on Panhard OHV flat-twin engines, which were converted to SOHC engines using components from Norton motorcycle engines. The first production car to use a timing belt

585-416: Is roughly in line with the top of the engine block . Modern engines with overhead valves or overhead camshaft(s) use the top of the piston (when it is near top dead centre ) as the bottom of the combustion chamber. Above this, the sides and roof of the combustion chamber include the intake valves, exhaust valves and spark plug. This forms a relatively compact combustion chamber without any protrusions to

630-551: The Duesenberg Model J , which was powered by a DOHC straight-eight engine. The 1931–1935 Stutz DV32 was another early American luxury car to use a DOHC engine. Also in the United States, the DOHC Offenhauser racing engine was introduced in 1933. This inline-four engine dominated North American open-wheel racing from 1934 until the 1970s. Other early SOHC automotive engines were the 1920–1923 Wolseley Ten ,

675-524: The Eunos 500 , also known as the Mazda Xedos 6 . It underwent no changes during its two-year production run, aside from the addition of the limited production Type X which received BBS cross-spoke alloy wheels. Overhead camshaft An overhead camshaft ( OHC ) engine is a piston engine in which the camshaft is located in the cylinder head above the combustion chamber . This contrasts with earlier overhead valve engines (OHV), where

720-465: The combustor . The combustor is fed with high pressure air by the compression system, adds fuel and burns the mix and feeds the hot, high pressure exhaust into the turbine components of the engine or out the exhaust nozzle. Different types of combustors exist, mainly: If the gas velocity changes, thrust is produced, such as in the nozzle of a rocket engine . Considering the definition of combustion chamber used for internal combustion engines,

765-537: The 1903 Marr Auto Car SOHC engine built in the United States. The first DOHC engine was a Peugeot inline-four racing engine which powered the car that won the 1912 French Grand Prix . Another Peugeot with a DOHC engine won the 1913 French Grand Prix , followed by the Mercedes-Benz 18/100 GP with an SOHC engine winning the 1914 French Grand Prix . The Isotta Fraschini Tipo KM — built in Italy from 1910–1914—

810-427: The 1925-1948 Velocette K series , the 1931-1957 Norton International and the 1947-1962 Norton Manx . In more recent times, the 1950-1974 Ducati Single , 1973-1980 Ducati L-twin engine , 1999-2007 Kawasaki W650 and 2011-2016 Kawasaki W800 motorcycle engines have used bevel shafts. The Crosley four cylinder was the last automotive engine to use the shaft tower design to drive the camshaft, from 1946 to 1952;

855-417: The 1928-1931 MG 18/80 , the 1926–1935 Singer Junior and the 1928–1929 Alfa Romeo 6C Sport . Early overhead camshaft motorcycles included the 1925–1949 Velocette K Series and the 1927–1939 Norton CS1 . The 1946–1948 Crosley CC Four was arguably the first American mass-produced car to use an SOHC engine. This small mass-production engine powered the winner of the 1950 12 Hours of Sebring . Use of

900-425: The Persona's interior, marketing the car under the tagline "Interiorism" ( インテリアイズム , Interiaizumu ) . It featured lounge-style door trims that appears completely integrated into the rear seats when the doors are closed, while the front seat belts were mounted in the rear doors to be as discreet as possible. It won a prize for "Best Car Interior" in 1988. Other unusual details were the absence of ashtrays as well as

945-399: The Persona, the ostensibly sportier Eunos version came with an ashtray and a lighter, as well as a different grille with a "V"-pattern rather than the fine mesh of the Persona. It received the more powerful upgraded 1.8-liter engine from the beginning, a few months earlier than the Persona did. The 2-liter option was the more powerful FE-ZE DOHC engine , producing 150 PS (110 kW) with

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990-519: The block, and were known as "tower shafts". An early American overhead camshaft production engine was the SOHC straight-eight engine used in the 1921–1926 Duesenberg Model A luxury car. In 1926, the Sunbeam 3 litre Super Sports became the first production car to use a DOHC engine. In the United States, Duesenberg added DOHC engines (alongside their existing SOHC engines) with the 1928 release of

1035-461: The camshaft (usually a timing chain in modern engines) is more complex in an OHC engine, such as the 4-chain valvetrain of the Audi 3.2 or the 2 meter chain on Ford cammers. Another disadvantage of OHC engines is that during engine repairs where the removal of the cylinder head is required, the camshaft engine timing needs to be reset. In addition, an OHC engine has a large cylinder head to accommodate

1080-408: The camshaft is located below the combustion chamber in the engine block . Single overhead camshaft (SOHC) engines have one camshaft per bank of cylinders . Dual overhead camshaft (DOHC, also known as "twin-cam" ) engines have two camshafts per bank. The first production car to use a DOHC engine was built in 1910. Use of DOHC engines slowly increased from the 1940s, leading to many automobiles by

1125-409: The camshaft is usually transferred to the valves either directly (using a tappet) or indirectly via a rocker arm . A dual overhead cam , double overhead cam , or twin-cam engine has two camshafts over each bank of the cylinder head, one for the intake valves and another for the exhaust valves. Therefore there are two camshafts for a straight engine and a total of four camshafts for a V engine or

1170-510: The camshaft or an extra set of valves to increase the volumetric efficiency , so that with the same displacement as an OHV engine, the OHC engine will end up being the physically larger of the two mostly due to the enlarged cylinder head. The other main advantage of OHC engines is that there is greater flexibility to optimise the size, location and shape of the intake and exhaust ports, since there are no pushrods that need to be avoided. This improves

1215-415: The camshaft. Timing belts are inexpensive, produce minimal noise and have no need for lubrication. A disadvantage of timing belts is the need for regular replacement of the belt; recommended belt life typically varies between approximately 50,000–100,000 km (31,000–62,000 mi). If the timing belt is not replaced in time and fails and the engine is an interference engine , major engine damage

1260-466: The crankshaft and the camshaft is commonly used in diesel overhead camshaft engines used in heavy trucks. Gear trains are not commonly used in engines for light trucks or automobiles. Several OHC engines up until the 1950s used a shaft with bevel gears to drive the camshaft. Examples include the 1908–1911 Maudslay 25/30 , the Bentley 3 Litre , the 1917-? Liberty L-12 , the 1929-1932 MG Midget ,

1305-443: The early 2000s using DOHC engines. In an OHC engine, the camshaft is located at the top of the engine, above the combustion chamber . This contrasts the earlier overhead valve engine (OHV) and flathead engine configurations, where the camshaft is located down in the engine block . The valves in both OHC and OHV engines are located above the combustion chamber; however an OHV engine requires pushrods and rocker arms to transfer

1350-457: The equivalent part of a steam engine would be the firebox , since this is where the fuel is burned. However, in the context of a steam engine, the term "combustion chamber" has also been used for a specific area between the firebox and the boiler . This extension of the firebox is designed to allow a more complete combustion of the fuel, improving fuel efficiency and reducing build-up of soot and scale. The use of this type of combustion chamber

1395-419: The form of a rotating output shaft). This contrasts an external combustion engine, where the combustion takes place in a separate part of the engine to where the gas pressure is converted into mechanical energy. In spark ignition engines, such as petrol (gasoline) engines , the combustion chamber is usually located in the cylinder head . The engines are often designed such that the bottom of combustion chamber

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1440-490: The gas flow through the engine, increasing power output and fuel efficiency . The oldest configuration of overhead camshaft engine is the single overhead camshaft (SOHC) design. A SOHC engine has one camshaft per bank of cylinders, therefore a straight engine has a total of one camshaft and a V engine or flat engine has a total of two camshafts (one for each cylinder bank). Most SOHC engines have two valves per cylinder, one intake valve and one exhaust valve. Motion of

1485-399: The gas flow) and turbulence , which improves the mixing and increases the flow rate of gasses. The shape of the piston top also affects the amount of swirl. Another design feature to promote turbulence for good fuel/air mixing is squish , where the fuel/air mix is "squished" at high pressure by the rising piston. The location of the spark plug is also an important factor, since this is

1530-407: The motion from the camshaft up to the valves, whereas an OHC engine has the valves directly actuated by the camshaft. Compared with OHV engines with the same number of valves, there are fewer reciprocating components and less valvetrain inertia in an OHC engine. This reduced inertia in OHC engines results in less valve float at higher engine speeds (RPM). A downside is that the system used to drive

1575-423: The piston). IOE engines combine elements of overhead valve and flathead engines; the intake valve is located above the combustion chamber, while the exhaust valve is located below it. The shape of the combustion chamber, intake ports and exhaust ports are key to achieving efficient combustion and maximising power output. Cylinder heads are often designed to achieve a certain "swirl" pattern (rotational component to

1620-454: The rights to the Crosley engine format were bought by a few different companies, including General Tire in 1952, followed by Fageol in 1955, Crofton in 1959, Homelite in 1961, and Fisher Pierce in 1966, after Crosley closed the automotive factory doors, and they continued to produce the same engine for several more years. A camshaft drive using three sets of cranks and rods in parallel

1665-409: The side (i.e. all of the chamber is located directly above the piston). Common shapes for the combustion chamber are typically similar to one or more half-spheres (such as the hemi , pent-roof , wedge or kidney-shaped chambers). The older flathead engine design uses a "bathtub"-shaped combustion chamber, with an elongated shape that sits above both the piston and the valves (which are located beside

1710-730: The starting point for both Mercedes' and Rolls-Royce's aircraft engines. Mercedes created a series of six-cylinder engines which culminated in the Mercedes D.III . Rolls-Royce reversed-engineered the Mercedes cylinder head design based on a racing car left in England at the beginning of the war, leading to the Rolls-Royce Eagle V12 engine. Other SOHC designs included the Spanish Hispano-Suiza 8 V8 engine (with

1755-700: The starting point of the flame front (the leading edge of the burning gasses) which then travels downwards towards the piston. Good design should avoid narrow crevices where stagnant "end gas" can become trapped, reducing the power output of the engine and potentially leading to engine knocking . Most engines use a single spark plug per cylinder, however some (such as the 1986-2009 Alfa Romeo Twin Spark engine ) use two spark plugs per cylinder. Compression-ignition engines, such as diesel engines , are typically classified as either: Direct injection engines usually give better fuel economy but indirect injection engines can use

1800-447: The timing between each camshaft and the crankshaft. This affords better fuel economy by allowing a broader torque curve. Although each major manufacturer has their own trade name for their specific system of variable cam phasing systems, overall they are all classified as variable valve timing . The rotation of a camshaft is driven by a crankshaft . Many 21st century engines use a toothed timing belt made from rubber and kevlar to drive

1845-437: The top of the engine. Large aircraft engines— particularly air-cooled engines— experienced considerable thermal expansion, causing the height of the cylinder block to vary during operating conditions. This expansion caused difficulties for pushrod engines, so an overhead camshaft engine using a shaft drive with sliding spline was the easiest way to allow for this expansion. These bevel shafts were usually in an external tube outside

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1890-414: The valves directly via a bucket tappet . A DOHC design permits a wider angle between intake and exhaust valves than in SOHC engines, which improves the air-fuel mixture's flow through the engine. A further benefit is that the spark plug can be placed at the optimum location, which in turn improves combustion efficiency . Another newer benefit of DOHC engine design is the ability to independently change/phase

1935-520: Was one of the first production cars to use an SOHC engine. During World War I, both the Allied and Central Powers ; specifically those of the German Empire 's Luftstreitkräfte air forces, sought to quickly apply the overhead camshaft technology of motor racing engines to military aircraft engines. The SOHC engine from the Mercedes 18/100 GP car (which won the 1914 French Grand Prix) became

1980-472: Was the 1962 Glas 1004 compact coupe. Another camshaft drive method commonly used on modern engines is a timing chain , constructed from one or two rows of metal roller chains . By the early 1960s most production automobile overhead camshaft designs used chains to drive the camshaft(s). Timing chains do not usually require replacement at regular intervals, however the disadvantage is that they are noisier than timing belts. A gear train system between

2025-474: Was used in the 1920–1923 Leyland Eight luxury car built in the United Kingdom. A similar system was used in the 1926-1930 Bentley Speed Six and the 1930-1932 Bentley 8 Litre . A two-rod system with counterweights at both ends was used by many models of the 1958-1973 NSU Prinz . Among the first overhead camshaft engines were the 1902 Maudslay SOHC engine built in the United Kingdom and

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