Petrol engine
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels. In most petrol engines, the fuel and air are mixed after compression; the pre-mixing was done in a carburetor, but now it is done by electronically controlled fuel injection, except in small engines where the cost/complication of electronics does not justify the added engine efficiency. The process differs from a diesel engine in the method of mixing the fuel and air, in using spark plugs to initiate the combustion process. In a diesel engine, only air is compressed, the fuel is injected into hot air at the end of the compression stroke, self-ignites; the first practical petrol engine was built in 1876 in Germany by Nikolaus August Otto, although there had been earlier attempts by Étienne Lenoir, Siegfried Marcus, Julius Hock and George Brayton. With both air and fuel in a closed cylinder, compressing the mixture too much poses the danger of auto-ignition — or behaving like a diesel engine.
Because of the difference in burn rates between the two different fuels, petrol engines are mechanically designed with different timing than diesels, so to auto-ignite a petrol engine causes the expansion of gas inside the cylinder to reach its greatest point before the cylinder has reached the "top dead center" position. Spark plugs are set statically or at idle at a minimum of 10 degrees or so of crankshaft rotation before the piston reaches T. D. C, but at much higher values at higher engine speeds to allow time for the fuel-air charge to complete combustion before too much expansion has occurred - gas expansion occurring with the piston moving down in the power stroke. Higher octane petrol burns slower, therefore it has a lower propensity to auto-ignite and its rate of expansion is lower. Thus, engines designed to run high-octane fuel can achieve higher compression ratios. Most modern automobile petrol engines have a compression ratio of 10.0:1 to 13.5:1. Engines with a knock sensor can and have C.
R higher than 11.1:1 and approaches 14.0:1 and engines without a knock sensor have C. R of 8.0:1 to 10.5:1. Petrol engines run at higher rotation speeds than diesels due to their lighter pistons, connecting rods and crankshaft and due to petrol burning more than diesel; because pistons in petrol engines tend to have much shorter strokes than pistons in diesel engines it takes less time for a piston in a petrol engine to complete its stroke than a piston in a diesel engine. However, the lower compression ratios of petrol engines give petrol engines lower efficiency than diesel engines. Most petrol engines have 20% thermal efficiency, nearly half of diesel engines; however some newer engines are reported to be much more efficient than previous spark-ignition engines. Petrol engines have many applications, including: Automobiles Motorcycles Aircraft Motorboats Small engines, such as lawn mowers and portable engine-generators Before the use of diesel engines became widespread, petrol engines were used in buses, lorries and a few railway locomotives.
Examples: Bedford OB bus Bedford M series lorry GE 57-ton gas-electric boxcab locomotive Petrol engines may run on the four-stroke cycle or the two-stroke cycle. For details of working cycles see: Four-stroke cycle Two-stroke cycle Wankel engine Common cylinder arrangements are from 1 to 6 cylinders in-line or from 2 to 16 cylinders in V-formation. Flat engines – like a V design flattened out – are common in small airplanes and motorcycles and were a hallmark of Volkswagen automobiles into the 1990s. Flat 6s are still used in many modern Porsches, as well as Subarus. Many flat engines are air-cooled. Less common, but notable in vehicles designed for high speeds is the W formation, similar to having 2 V engines side by side. Alternatives include rotary and radial engines the latter have 7 or 9 cylinders in a single ring, or 10 or 14 cylinders in two rings. Petrol engines may be air-cooled, with fins; the coolant was water, but is now a mixture of water and either ethylene glycol or propylene glycol.
These mixtures have lower freezing points and higher boiling points than pure water and prevent corrosion, with modern antifreezes containing lubricants and other additives to protect water pump seals and bearings. The cooling system is slightly pressurized to further raise the boiling point of the coolant. Petrol engines use spark ignition and high voltage current for the spark may be provided by a magneto or an ignition coil. In modern car engines the ignition timing is managed by an electronic Engine Control Unit; the most common way of engine rating is what is known as the brake power, measured at the flywheel, given in kilowatts or horsepower. This is the actual mechanical power output of the engine in a complete form; the term "brake" comes from the use of a brake in a dynamometer test to load the engine. For accuracy, it is important to understand what is meant by complete. For example, for a car engine, apart from friction and thermodynamic losses inside the engine, power is absorbed by the water pump and radiator fan, thus reducing the power available at the flywheel to move the car along.
Power is abso
Cylinder head
In an internal combustion engine, the cylinder head sits above the cylinders on top of the cylinder block. It closes in the top of the cylinder; this joint is sealed by a head gasket. In most engines, the head provides space for the passages that feed air and fuel to the cylinder, that allow the exhaust to escape; the head can be a place to mount the valves, spark plugs, fuel injectors. In a flathead or sidevalve engine, the mechanical parts of the valve train are all contained within the block, a'poultice head' may be used, a simple metal plate bolted to the top of the block. Keeping all moving parts within the block has an advantage for physically large engines in that the camshaft drive gear is small and so suffers less from the effects of thermal expansion in the cylinder block. With a chain drive to an overhead camshaft, the extra length of chain needed for an overhead cam design could give trouble from wear and slop in the chain without frequent maintenance. Early sidevalve engines were in use at a time of simple fuel chemistry, low octane ratings and so required low compression ratios.
This made their combustion chamber design less critical and there was less need to design their ports and airflow carefully. One difficulty experienced at this time was that the low compression ratio implied a low expansion ratio during the power stroke. Exhaust gases were thus still hot, hotter than a contemporary engine, this led to frequent trouble with burnt exhaust valves. A major improvement to the sidevalve engine was the advent of Ricardo's turbulent head design; this reduced the space within the combustion chamber and the ports, but by careful thought about the airflow paths within them it allowed a more efficient flow in and out of the chamber. Most it used turbulence within the chamber to mix the fuel and air mixture. This, of itself, allowed the use of higher compression ratios and more efficient engine operation; the limit on sidevalve performance is not the gas flow through the valves, but rather the shape of the combustion chamber. With high speed engines and high compression, the limiting difficulty becomes that of achieving complete and efficient combustion, whilst avoiding the problems of unwanted pre-detonation.
The shape of a sidevalve combustion chamber, being wider than the cylinder to reach the valve ports, conflicts with achieving both an ideal shape for combustion and the small volume needed for high compression. Modern, efficient engines thus tend towards the pent roof or hemi designs, where the valves are brought close in to the centre of the space. Where fuel quality is low and octane rating is poor, compression ratios will be restricted. In these cases, the sidevalve engine still has much to offer. In the case of the developed IOE engine for a market with poor fuels, engines such as Rolls-Royce B series or the Land-Rover use a complicated arrangement of inclined valves, a cylinder head line at an angle to the bore and corresponding angled pistons to provide a compact combustion chamber approaching the near-hemispherical ideal; such engines remained in production into the 1990s, only being replaced when the fuels available'in the field' became more to be diesel than petrol. Internally, the cylinder head has passages called ports or tracts for the fuel/air mixture to travel to the inlet valves from the intake manifold, for exhaust gases to travel from the exhaust valves to the exhaust manifold.
In a water-cooled engine, the cylinder head contains integral ducts and passages for the engines' coolant—usually a mixture of water and antifreeze—to facilitate the transfer of excess heat away from the head, therefore the engine in general. In the overhead valve design, the cylinder head contains the poppet valves and the spark plugs, along with tracts or'ports' for the inlet and exhaust gases; the operation of the valves is initiated by the engine's camshaft, sited within the cylinder block, its moment of operation is transmitted to the valves' pushrods, rocker arms mounted on a rocker shaft—the rocker arms and shaft being located within the cylinder head. In the overhead camshaft design, the cylinder head contains the valves, spark plugs and inlet/exhaust tracts just like the OHV engine, but the camshaft is now contained within the cylinder head; the camshaft may be seated centrally between each offset row of inlet and exhaust valves, still utilizing rocker arms, or the camshaft may be seated directly above the valves eliminating the rocker arms and utilizing'bucket' tappets.
The number of cylinder heads in an engine is a function of the engine configuration. All inline engines today use a single cylinder head that serves all the cylinders. A V engine has two cylinder heads, one for each cylinder bank of the'V'. For a few compact'narrow angle' V engines, such as the Volkswagen VR6, the angle between the cylinder banks is so narrow that it uses a single head spanning the two banks. A flat engine has two heads. Most radial engines have one head for each cylinder, although this is of the monobloc form wherein the head is made as an integral part of the cylinder; this is common for motorcycles, such head/cylinder components are referred-to as barrels. Some engines medium- and large-capacity diesel engines built for industrial, power generation, heavy traction purposes have individual cylinder heads for each cylinder; this reduces repair costs as a single failed head on a
Connecting rod
A connecting rod is a rigid member which connects a piston to a crank or crankshaft in a reciprocating engine. Together with the crank, it forms a simple mechanism that converts reciprocating motion into rotating motion. A connecting rod may convert rotating motion into reciprocating motion, its original use. Earlier mechanisms, such as the chain, could only impart pulling motion. Being rigid, a connecting rod may transmit either push or pull, allowing the rod to rotate the crank through both halves of a revolution. In a few two-stroke engines the connecting rod is only required to push. Today, the connecting rod is best known through its use in internal combustion piston engines, such as automobile engines; these are of a distinctly different design from earlier forms of connecting rod used in steam engines and steam locomotives. Evidence for the connecting rod appears in the late 3rd century Hierapolis sawmill in Roman Asia, it appears in two 6th century Byzantine-era saw mills excavated at Ephesus, Asia Minor and Gerasa, Roman Syria.
The crank and connecting rod mechanism of these Roman-era watermills converted the rotary motion of the waterwheel into the linear movement of the saw blades. Sometime between 1174 and 1206 in the Artuqid State, the Arab inventor and engineer Al-Jazari described a machine which incorporated the connecting rod with a crankshaft to pump water as part of a water-raising machine, though the device was complex. In Renaissance Italy, the earliest evidence of a − albeit mechanically misunderstood − compound crank and connecting-rod is found in the sketch books of Taccola. A sound understanding of the motion involved is displayed by the painter Pisanello who showed a piston-pump driven by a water-wheel and operated by two simple cranks and two connecting-rods. By the 16th century, evidence of cranks and connecting rods in the technological treatises and artwork of Renaissance Europe becomes abundant; the first steam engine, Newcomen's atmospheric engine, was single-acting: its piston only did work in one direction and so these used a chain rather than a connecting rod.
Their output rocked forth, rather than rotating continuously. Steam engines after this are double-acting: their internal pressure works on each side of the piston in turn; this requires a seal around the piston rod and so the hinge between the piston and connecting rod is placed outside the cylinder, in a large sliding bearing block called a crosshead. In a steam locomotive, the crank pins are mounted directly on one or more pairs of driving wheels, the axle of these wheels serves as the crankshaft; the connecting rods, run between the crank pins and crossheads, where they connect to the piston rods. Crossheads or trunk guides are used on large diesel engines manufactured for marine service; the connecting rods of smaller steam locomotives are of rectangular cross-section but, on small locomotives, marine-type rods of circular cross-section have been used. Stephen Lewin, who built both locomotive and marine engines, was a frequent user of round rods. Gresley's A4 Pacifics, such as Mallard, had an alloy steel connecting rod in the form of an I-beam with a web, only 0.375 in thick.
On Western Rivers steamboats, the connecting rods are properly called pitmans, are sometimes incorrectly referred to as pitman arms. In modern automotive internal combustion engines, the connecting rods are most made of steel for production engines, but can be made of T6-2024 and T651-7075 aluminum alloys or titanium for high-performance engines, or of cast iron for applications such as motor scooters, they are not rigidly fixed at either end, so that the angle between the connecting rod and the piston can change as the rod moves up and down and rotates around the crankshaft. Connecting rods in racing engines, may be called "billet" rods, if they are machined out of a solid billet of metal, rather than being cast or forged; the small end attaches to the piston pin, gudgeon pin or wrist pin, most press fit into the connecting rod but can swivel in the piston, a "floating wrist pin" design. The big end connects to the crankpin on the crank throw, in most engines running on replaceable bearing shells accessible via the connecting rod bolts which hold the bearing "cap" onto the big end.
There is a pinhole bored through the bearing on the big end of the connecting rod so that pressurized lubricating motor oil squirts out onto the thrust side of the cylinder wall to lubricate the travel of the pistons and piston rings. Most small two-stroke engines and some single cylinder four-stroke engines avoid the need for a pumped lubrication system by using a rolling-element bearing instead, however this requires the crankshaft to be pressed apart and back together in order to replace a connecting rod. A major source of engine wear is the sideways force exerted on the piston through the connecting rod by the crankshaft, which wears the cylinder into an oval cross-section rather than circular, making it impossible for piston rings to seal against the cylinder walls. Geometrically, it can be seen that longer connecting rods will reduce the amount of this sideways force, therefore lead to longer engine life
Mazda Wankel engine
The Mazda Wankel engines are a family of Wankel rotary combustion car engines produced by Mazda. Wankel engines were invented in the early 1960s by a German engineer. Over the years, displacement has been increased and turbocharging has been added. Mazda rotary engines have a reputation for being small and powerful at the expense of poor fuel efficiency; the engines became popular with kit car builders, hot rodders and in light aircraft because of their light weight, compact size, tuning potential and inherently high power-to-weight ratio—as is true for all Wankel-type engines. Mazda put the engine into series production with NSU and Citroën as part of the Comotor joint-venture between 1967 and 1977. Since the end of production of the Mazda RX-8 in 2012, the engine is produced only for single seater racing, with the one-make Star Mazda Championship being contested with a Wankel engine until 2017. Wankel engines can be classified by their geometric size in terms of radius and depth, offset; these metrics function to the bore and stroke measurements of a piston engine.
Displacement is 3√3radius·offset·depth, multiplied with the number of rotors. Nearly all Mazda production Wankel engines share a single rotor radius, 105 mm, with a 15 mm crankshaft offset; the only engine to diverge from this formula was the rare 13A, which used a 120 mm rotor radius and 17.5 mm crankshaft offset. As Wankel engines became commonplace in motor sport events, the problem of representing each engine's displacement for the purposes of competition arose. Rather than force the majority of participants to halve their quoted displacement, most racing organizations decided to double the quoted displacement of Wankel engines; the key for comparing the displacement between the 4-cycle engine and the rotary engine is in studying the degrees of rotation for a thermodynamic cycle to occur. For a 4-cycle engine to complete every thermodynamic cycle, the engine must rotate 720° or two complete revolutions of the crankshaft; the rotary engine is different. The engine rotor rotates at 1/3 the speed of the crankshaft.
On two rotor engines and rear rotors are 180° offset from each other. Each rotation of the engine will bring two faces through the combustion cycle; this said, it takes 1080° or three complete revolutions of the crankshaft to complete the entire thermodynamic cycle. There is a disparity. How can we get a relatable number to compare to a 4-stroke engine? The best way is to study 720° of rotation of the two-rotor engine; every 360° of rotation, two faces of the engine complete a combustion cycle. 720° will have a total of four faces completing their cycle. 654 cc per face times four faces equals 2.6 160 cu in. That now gives something that can be compared to other engines. In addition, since four faces passed by in the comparison, it’s like a four-cylinder engine; the 13B therefore compares well to a 2.6L 4-cylinder 4-cycle engine. By using the same formula, calculating actual displacement in which 1080° is the complete thermodynamic cycle of a rotary engine and a total of six faces completing their cycle, 654 cc per face times six faces equals 3,924 cc, in reference to a Mazda 13B rotary engine.
"Each face has a swept volume of 654 cc and there are a total of six faces. With this known, the engine displacement should be 654 cc times six to equal 3,924 cc or 3.9 L or 239.5 cu in." Mazda's first prototype Wankel was the 40A, a single-rotor engine much like the NSU KKM400. Although never produced in volume, the 40A was a valuable testbed for Mazda engineers, demonstrated two serious challenges to the feasibility of the design: "chatter marks" in the housing, heavy oil consumption; the chatter marks, nicknamed "devil's fingernails", were caused by the tip-seal vibrating at its natural frequency. The oil consumption problem was addressed with heat-resistant rubber oil seals at the sides of the rotors; this early engine had a rotor radius of 90 mm, an offset of 14 mm, a depth of 59 mm. The first Mazda Cosmo prototype used a 798 cc L8A two-rotor Wankel; the engine and car were both shown at the 1963 Tokyo Motor Show. Hollow cast iron apex seals reduced vibration by changing their resonance frequency and thus eliminated chatter marks.
It used dry-sump lubrication. Rotor radius was up from the 40A to 98 mm. One-, three-, four-rotor derivatives of the L8A were created for experimentation; the 10A series was Mazda's first production Wankel, appearing in 1965. It was a two-rotor design, with each chamber displacing 491 cc so two chambers would displace 982 cc; these engines featured the mainstream rotor dimensions with a 60 mm depth. The rotor housing was made of sand-cast aluminum plated with chrome, while
Carburetor
A carburetor or carburettor is a device that mixes air and fuel for internal combustion engines in the proper air–fuel ratio for combustion. It is sometimes colloquially shortened to carby in Australia. To carburate or carburet means to mix the air and fuel or to equip with a carburetor for that purpose. Carburetors have been supplanted in the automotive and, to a lesser extent, aviation industries by fuel injection, they are still common on small engines for lawn mowers and other equipment. The word carburetor comes from the French carbure meaning "carbide". Carburer means to combine with carbon. In fuel chemistry, the term has the more specific meaning of increasing the carbon content of a fluid by mixing it with a volatile hydrocarbon; the first carburetor was invented by Samuel Morey in 1826. The first person to patent a carburetor for use in a petroleum engine was Siegfried Marcus with his 6 July 1872 patent for a device which mixes fuel with air. A carburetor was among the early patents by Karl Benz as he developed internal combustion engines and their components.
Early carburetors were of the surface type, in which air is combined with fuel by passing over the surface of gasoline. In 1885, Wilhelm Maybach and Gottlieb Daimler developed a float carburetor based on the atomizer nozzle; the Daimler-Maybach carburetor was copied extensively. British courts rejected the Daimler company's claim of priority in favor of Edward Butler's 1884 spray carburetor used on his Petrol Cycle. Hungarian engineers János Csonka and Donát Bánki patented a carburetor for a stationary engine in 1893. Frederick William Lanchester of Birmingham, experimented with the wick carburetor in cars. In 1896, Frederick and his brother built a gasoline-driven car in England, a single cylinder 5 hp internal combustion engine with chain drive. Unhappy with the car's performance and power, they re-designed the engine the following year using two horizontally-opposed cylinders and a newly designed wick carburetor. Carburetors were the common method of fuel delivery for most US-made gasoline engines until the late 1980s, when fuel injection became the preferred method.
This change was dictated by the requirements of catalytic converters and not due to an inherent inefficiency of carburation. A catalytic converter requires that there be more precise control over the fuel / air mixture in order to control the amount of oxygen remaining in the exhaust gases. In the U. S. market, the last cars using carburetors were: 1990: Oldsmobile Custom Cruiser, Buick Estate Wagon, Cadillac Brougham, Honda Prelude, Subaru Justy 1991: Ford Crown Victoria Police Interceptor with the 5.8 L V8 engine. 1991: Jeep Grand Wagoneer with the AMC 360 cu in V8 engine. 1993: Mazda B2200 1994: IsuzuIn Australia, some cars continued to use carburetors well into the 1990s. Low-cost commercial vans and 4WDs in Australia continued with carburetors into the 2000s, the last being the Mitsubishi Express van in 2003. Elsewhere, certain Lada cars used carburetors until 2006. Many motorcycles still use carburetors for simplicity's sake, since a carburetor does not require an electrical system to function.
Carburetors are still found in small engines and in older or specialized automobiles, such as those designed for stock car racing, though NASCAR's 2011 Sprint Cup season was the last one with carbureted engines. In Europe, carburetor-engined cars were being phased out by the end of the 1980s in favor of fuel injection, the established type of engine on more expensive vehicles including luxury and sports models. EEC legislation required all vehicles sold and produced in member countries to have a catalytic converter after December 1992; this legislation had been in the pipeline for some time, with many cars becoming available with catalytic converters or fuel injection from around 1990. However, some versions of the Peugeot 106 were sold with carburettor engines from its launch in 1991, as were versions of the Renault Clio and Nissan Primera and all versions of Ford Fiesta range except the XR2i when it was launched in 1989. Luxury car manufacturer Mercedes-Benz had been producing mechanically fuel-injected cars since the early 1950s, while the first mainstream family car to feature fuel injection was the Volkswagen Golf GTI in 1976.
Ford's first fuel-injected car was the Ford Capri RS 2600 in 1970. General Motors launched its first fuel-injected car in 1957 as an option available for the first generation Corvette. Saab switched to fuel injection across its whole range from 1982; the carburetor works on Bernoulli's principle: the faster air moves, the lower its static pressure, higher the dynamic pressure is. The throttle linkage does not directly control the flow of liquid fuel. Instead, it actuates carburetor mechanisms which meter the flow of air being carried into the engine; the speed of this flow, therefore its pressure, determines the amount of fuel drawn into the airstream. When carburetors are used in aircraft with piston engines, special designs and features are needed to prevent fuel starvation during inverted flight. Engines used an early form of fuel injection known as a pressure carburetor. Most production carbureted engines, as opposed to fuel-injected, h
Valvetrain
A valvetrain or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly. A conventional reciprocating internal combustion engine uses valves to control the flow of the air/fuel admix into and out of the combustion chamber. A typical ohv valvetrain consists of valves, rocker arms, pushrods and camshaft. Valvetrain opening/closing and duration, as well as the geometry of the valvetrain, controls the amount of air and fuel entering the combustion chamber at any given point in time. Timing for open/close/duration is controlled by the camshaft, synchronized to the crankshaft by a chain, belt, or gear. Valvetrains are built in several configurations, each of which varies in layout but still performs the task of opening and closing the valves at the time necessary for proper operation of the engine; these layouts are differentiated by the location of the camshaft within the engine: Cam-in-block The camshaft is located within the engine block, operates directly on the valves, or indirectly via pushrods and rocker arms.
Because they require pushrods they are called pushrod engines. Overhead camshaft The camshaft is located above the valves within the cylinder head, operates either indirectly or directly on the valves. Camless This layout uses no camshafts at all. Technologies such as solenoids are used to individually actuate the valves; the valvetrain is the mechanical system responsible for operation of the valves. Valves are of the poppet type, although many others have been developed such as sleeve and rotary valves. Poppet valves require small coil springs, appropriately named valve springs, to keep them closed when not actuated by the camshaft, they are attached to the valve stem ends, seating within spring retainers. Other mechanisms can be used in place of valve springs to keep the valves closed: Formula 1 engines employ pneumatic valve springs in which pneumatic pressure closes the valves, while motorcycle manufacturer Ducati uses desmodromic valve drive which mechanically close the valves. Depending on the design used, the valves are actuated directly by a rocker arm, finger, or bucket tappet.
Overhead camshaft engines use fingers or bucket tappets, upon which the cam lobes contact, while pushrod engines use rocker arms. Rocker arms are actuated by a pushrod, pivot on a shaft or individual ball studs in order to actuate the valves. Pushrods are slender metal rods seated within the engine block. At the bottom ends the pushrods are fitted with lifters, either solid or hydraulic, upon which the camshaft, located within the cylinder block, makes contact; the camshaft pushes on the lifter, which pushes on the pushrod, which pushes on the rocker arm, which rotates and pushes down on the valve. Camshafts must actuate the valves at the appropriate time in the combustion cycle. In order to accomplish this the camshaft is linked to and kept in synchronisation with the crankshaft through the use of a metal chain, rubber belt, or geartrain; because these mechanisms are essential to the proper timing of valve actuation they are named timing chains, timing belts, timing gears, respectively. Typical normal-service engine valve-train components may be too lightweight for operating at high revolutions per minute, leading to valve float.
This occurs when the action of the valve no longer opens or closes, such as when the valve spring force is insufficient to close the valve causing a loss of control of the valvetrain, as well as a drop in power output. Valve float will damage the valvetrain over time, could cause the valve to be damaged as it is still open while the piston comes to the top of its stroke. Upgrading to high pressure valve springs could allow higher valvetrain speeds, but this would overload the valvetrain components and cause excessive and costly wear. High-output and engines used in competition feature camshafts and valvetrain components that are designed to withstand higher RPM ranges; these changes include additional modifications such as larger-sized valves combined with freer breathing intake and exhaust ports to improve air flow. Automakers offer factory-approved performance parts to increase engine output, numerous aftermarket parts vendors specialize in valvetrain modifications for various engine applications.
Cam-in-block Overhead camshaft Camless Animation
Overhead valve engine
An overhead valve engine, or "pushrod engine", is a reciprocating piston engine whose poppet valves are sited in the cylinder head. An OHV engine's valvetrain operates its valves via a camshaft within the cylinder block, cam followers and rocker arms; the OHV engine was an advance over the older flathead engine, whose valves were sited within the cylinder block. Some early "OHV" engines known as "F-heads" used both side-valves and overhead valves. A variation over the OHV design is the overhead camshaft, or "OHC", whose camshaft lies in the cylinder head itself, above the valves. To avoid confusion, OHC engines are not referred to as OHV despite having their valves in the head. In early 1894, Rudolf Diesel's second Diesel engine prototype was built with a cylinder head featuring push rods, rocker arms, poppet valves. Diesel had published this design in 1893. In 1896, U. S. patent 563,140, awarded to William F. Davis, illustrated a gasoline engine with the same head configuration, patenting his solution to the problem of how to cool the head, which problem had made the overhead valve engine difficult before then.
Henry Ford's Quadricycle of 1896 had valves in the head, with push rods for exhaust valves only, the intake using suction valves. In 1898, Detroit bicycle manufacturer Walter Lorenzo Marr built a motor-trike with a one-cylinder OHV engine with push rods for both exhaust and intake. In 1900, David Buick hired Marr as chief engineer at the Buick Auto-Vim and Power Company in Detroit, where he worked until 1902. Marr's engine employed pushrod-actuated rocker arms, which in turn pushed valves parallel to the pistons. Marr left Buick to start his own automobile company in 1902, the Marr Auto-Car, made a handful of cars with overhead valve engines, before coming back to Buick in 1904; the OHV engine was patented in 1902 by Buick's second chief engineer Eugene Richard, at the Buick Manufacturing Company, precursor to the Buick Motor Company. The world's first production overhead valve internal combustion engine was put into the first production Buick automobile, the 1904 Model B, which used a 2-cylinder Flat twin engine, with 2 valves in each head.
The engine was designed by David Buick. Eugene Richard of the Buick Manufacturing Company was awarded US Patent #771,095 in 1904 for the valve in head engine, it included rocker arms and push rods, a water jacket for the head which communicated with the one in the cylinder block, lifters pushed by a camshaft with a 2-to-1 gearing ratio to the crankshaft. Arthur Chevrolet was awarded US Patent #1,744,526 for an adapter that could be applied to an existing engine, thus transforming it into an Overhead Valve Engine; the Wright Brothers built their own airplane engines, starting in 1906, they used overhead valves for both exhaust and intake, with push rods and rocker arms for the exhaust valves only, the intake valves being "automatic suction" valves. They built a V-8 engine with this valve configuration in 1910. In 1949, Oldsmobile introduced the Rocket V8, the first V-8 engine with OHV's to be produced on a wide scale. General Motors is the world's largest pushrod engine producer, producing I4, V6 and V8 pushrod engines.
Most other companies use overhead cams. Nowadays, automotive use of side-valves has disappeared, valves are all "overhead". However, most are now driven more directly by the overhead camshaft system. Few pushrod-type engines remain in production outside of the United States market; this is in part a result of some countries passing laws to tax engines based on displacement, because displacement is somewhat related to the emissions and fuel efficiency of an automobile. This has given OHC engines a regulatory advantage in those countries, which resulted in few manufacturers wanting to design both OHV and OHC engines. However, in 2002, Chrysler introduced a new pushrod engine: a 5.7-litre Hemi engine. The new Chrysler Hemi engine presents advanced features such as variable displacement technology and has been a popular option with buyers; the Hemi was on the Ward's 10 Best Engines list for 2003 through 2007. Chrysler produced the world's first production variable-valve OHV engine with independent intake and exhaust phasing.
The system is called CamInCam, was first used in the 600 horsepower SRT-10 engine for the 2008 Dodge Viper. Early air-cooled ohv BMW boxer motorcycle engines had long pushrods and a single centrally-mounted camshaft; the pushrods were short, allowing higher rpm and more power. For instance, the BMW R1100S could achieve an output of 98 hp at 8,400 rpm, with no risk of valve bounce. Since 2013, BMW flat-twin motorcycle engines have had OHC valve actuation. OHV engines have some advantages over OHC engines: Smaller overall packaging: because of the camshaft's location inside the engine block, OHV engines are more compact than an overhead cam engine of comparable displacement. For example, Ford's 4.6 L OHC modular V8 is larger than the 5.0 L I-head Windsor V8. GM's 4.6 L OHC Northstar V8 is taller and wider than GM's larger displacement 5.7 to 7.0 L I-head LS V8. The Ford Ka uses the Kent Crossflow/Endura-E OHV engine to fit under its low bonnet line; because of the more compact size of an engine of a given displacement, a pushrod engine of given external dimensions can have greater displacement than an OHC engine of the same external size.
As a result, the pushrod engine can sometimes produce just as much power as the OHC engine, but with greater torque (contrary to popular belief, this is due to the greater displacement of
