A fuel pump is a essential component on a car or other internal combustion engined device. Many engines do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank or under high pressure to the fuel injection system. Carbureted engines use low pressure mechanical pumps that are mounted outside the fuel tank, whereas fuel injected engines use electric fuel pumps that are mounted inside the fuel tank. Fuel pressure needs to be within certain specifications for the engine to run correctly. If the fuel pressure is too high, the engine will run rough and rich, not combusting all of the fuel being pumped making the engine inefficient and a pollutant. If the pressure is too low, the engine may misfire, or stall. Prior to the widespread adoption of electronic fuel injection, most carbureted automobile engines used mechanical fuel pumps to transfer fuel from the fuel tank into the fuel bowls of the carburetor; the two most used fuel feed pumps are diaphragm and plunger-type mechanical pumps.
Diaphragm pumps are a type of positive displacement pump. Diaphragm pumps contain a pump chamber whose volume is increased or decreased by the flexing of a flexible diaphragm, similar to the action of a piston pump. A check valve is located at both the inlet and outlet ports of the pump chamber to force the fuel to flow in one direction only. Specific designs vary, but in the most common configuration, these pumps are bolted onto the engine block or head, the engine's camshaft has an extra eccentric lobe that operates a lever on the pump, either directly or via a pushrod, by pulling the diaphragm to bottom dead center. In doing so, the volume inside the pump chamber increased; this allows fuel to be pushed into the pump from the tank. The return motion of the diaphragm to top dead center is accomplished by a diaphragm spring, during which the fuel in the pump chamber is squeezed through the outlet port and into the carburetor; the pressure at which the fuel is expelled from the pump is thus limited by the force applied by the diaphragm spring.
The carburetor contains a float bowl into which the expelled fuel is pumped. When the fuel level in the float bowl exceeds a certain level, the inlet valve to the carburetor will close, preventing the fuel pump from pumping more fuel into the carburetor. At this point, any remaining fuel inside the pump chamber is trapped, unable to exit through the inlet port or outlet port; the diaphragm will continue to allow pressure to the diaphragm, during the subsequent rotation, the eccentric will pull the diaphragm back to bottom dead center, where it will remain until the inlet valve to the carburetor reopens. Because one side of the pump diaphragm contains fuel under pressure and the other side is connected to the crankcase of the engine, if the diaphragm splits, it can leak fuel into the crankcase; the capacity of both mechanical and electric fuel pump is measured in psi. This unit is the general measurement for pressure, yet it has different meaning, when talking about fuel pumps. In this context it denotes the speed.
This is one of fuel pump characteristics. The higher pressure is. Plunger-type pumps are a type of positive displacement pump that contain a pump chamber whose volume is increased and/or decreased by a plunger moving in and out of a chamber full of fuel with inlet and discharge stop-check valves, it is similar to that of a piston pump, but the high-pressure seal is stationary while the smooth cylindrical plunger slides through the seal. These pumps run at a higher pressure than diaphragm type pumps. Specific designs vary, but in the most common configuration, these pumps are mounted on the side of the injection pump and driven by the camshaft, either directly or via a pushrod; when the camshaft lobe is at top dead center, the plunger has just finished pushing the fuel through the discharge valve. A spring is used to pull the plunger outward creating a lower pressure pulling fuel into the chamber from the inlet valve; these pumps can run between 1,800 bar. Because it is connected to the camshaft, the discharge pressure of these pumps is constant, but the rate at which it pumps is directly correlated to the revolutions per minute of the engine.
Both pumps create negative pressure to draw the fuel through the lines. However, the low pressure between the pump and the fuel tank, in combination with heat from the engine and/or hot weather, can cause the fuel to vaporize in the supply line; this results in fuel starvation as the fuel pump, designed to pump liquid, not vapor, is unable to suck more fuel to the engine, causing the engine to stall. This condition is different from vapor lock, where high engine heat on the pressured side of the pump boils the fuel in the lines starving the engine of enough fuel to run. Mechanical automotive fuel pumps do not generate much more than 10–15 psi, more than enough for most carburetors; as engines moved away from carburetors and towards fuel injection, mechanical fuel pumps were replaced with electric fuel pumps, because fuel injection systems operate more efficiently at higher fuel pressures than mechanical diaphragm pumps can generate. Electric fuel pumps are located in the fuel tank, in order
Internal combustion engine
An internal combustion engine is a heat engine where the combustion of a fuel occurs with an oxidizer in a combustion chamber, an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine; the force is applied to pistons, turbine blades, rotor or a nozzle. This force moves the component over a distance, transforming chemical energy into useful mechanical energy; the first commercially successful internal combustion engine was created by Étienne Lenoir around 1859 and the first modern internal combustion engine was created in 1876 by Nikolaus Otto. The term internal combustion engine refers to an engine in which combustion is intermittent, such as the more familiar four-stroke and two-stroke piston engines, along with variants, such as the six-stroke piston engine and the Wankel rotary engine. A second class of internal combustion engines use continuous combustion: gas turbines, jet engines and most rocket engines, each of which are internal combustion engines on the same principle as described.
Firearms are a form of internal combustion engine. In contrast, in external combustion engines, such as steam or Stirling engines, energy is delivered to a working fluid not consisting of, mixed with, or contaminated by combustion products. Working fluids can be air, hot water, pressurized water or liquid sodium, heated in a boiler. ICEs are powered by energy-dense fuels such as gasoline or diesel fuel, liquids derived from fossil fuels. While there are many stationary applications, most ICEs are used in mobile applications and are the dominant power supply for vehicles such as cars and boats. An ICE is fed with fossil fuels like natural gas or petroleum products such as gasoline, diesel fuel or fuel oil. There is a growing usage of renewable fuels like biodiesel for CI engines and bioethanol or methanol for SI engines. Hydrogen is sometimes used, can be obtained from either fossil fuels or renewable energy. Various scientists and engineers contributed to the development of internal combustion engines.
In 1791, John Barber developed the gas turbine. In 1794 Thomas Mead patented a gas engine. In 1794, Robert Street patented an internal combustion engine, the first to use liquid fuel, built an engine around that time. In 1798, John Stevens built the first American internal combustion engine. In 1807, French engineers Nicéphore and Claude Niépce ran a prototype internal combustion engine, using controlled dust explosions, the Pyréolophore; this engine powered a boat on France. The same year, the Swiss engineer François Isaac de Rivaz built an internal combustion engine ignited by an electric spark. In 1823, Samuel Brown patented the first internal combustion engine to be applied industrially. In 1854 in the UK, the Italian inventors Eugenio Barsanti and Felice Matteucci tried to patent "Obtaining motive power by the explosion of gases", although the application did not progress to the granted stage. In 1860, Belgian Jean Joseph Etienne Lenoir produced a gas-fired internal combustion engine. In 1864, Nikolaus Otto patented the first atmospheric gas engine.
In 1872, American George Brayton invented the first commercial liquid-fuelled internal combustion engine. In 1876, Nikolaus Otto, working with Gottlieb Daimler and Wilhelm Maybach, patented the compressed charge, four-cycle engine. In 1879, Karl Benz patented a reliable two-stroke gasoline engine. In 1886, Karl Benz began the first commercial production of motor vehicles with the internal combustion engine. In 1892, Rudolf Diesel developed compression ignition engine. In 1926, Robert Goddard launched the first liquid-fueled rocket. In 1939, the Heinkel He 178 became the world's first jet aircraft. At one time, the word engine meant any piece of machinery—a sense that persists in expressions such as siege engine. A "motor" is any machine. Traditionally, electric motors are not referred to as "engines". In boating an internal combustion engine, installed in the hull is referred to as an engine, but the engines that sit on the transom are referred to as motors. Reciprocating piston engines are by far the most common power source for land and water vehicles, including automobiles, ships and to a lesser extent, locomotives.
Rotary engines of the Wankel design are used in some automobiles and motorcycles. Where high power-to-weight ratios are required, internal combustion engines appear in the form of combustion turbines or Wankel engines. Powered aircraft uses an ICE which may be a reciprocating engine. Airplanes can instead use jet engines and helicopters can instead employ turboshafts. In addition to providing propulsion, airliners may employ a separate ICE as an auxiliary power unit. Wankel engines are fitted to many unmanned aerial vehicles. ICEs drive some of the large electric generators, they are found in the form of combustion turbines in combined cycle power plants with a typical electrical output in the range of 100 MW to 1 GW. The high temperature exhaust is used to superheat water to run a steam turbine. Thus, the efficiency is higher because more energy is extracted from the fuel than what could be extracted by the co
Internal combustion piston engines are arranged so that the cylinders are in lines parallel to the crankshaft. Where they are in a single line, this is referred to as an straight engine. Where engines have a large number of cylinders, the cylinders are arranged in two lines, placed at an angle to each other as a V engine; each line is referred to as a cylinder bank. The angle between cylinder banks is described as the bank angle. Engines with six cylinders are common as either straight or vee engines. With more cylinders than this, the vee configuration is more common. Fewer cylinders are more arranged as an inline engine. There are exceptions to this: straight-8 engines were found on some pre-war luxury cars with the bonnet length to house them. A few V4 engines have been produced where an extra-compact engine was required, including some outboard motors with a vertical crankshaft. Although twin-cylinder engines are now rare for cars, they are still used for motorcycles and the vee-twin and inline twin are both used.
An obvious advantage to a multi-bank engine is. This allows a torsionally stiffer construction for both the crankcase; the most important advantage though is less obvious: a multi-plane engine can be arranged to have better balance and less vibration. This depends on the layout of the crankshaft more than the cylinder banks alone: the planes on which the pistons are arranged, thus their timing and vibration, depend on both the cylinder bank and the crankshaft angles; the W or broad arrow arrangement uses three cylinder banks a W-12 with three banks of four cylinders. Narrow-angle vee engines, such as the Lancia V4 and the Volkswagen VR6, have such a narrow bank angle that their cylinders are combined into a single cylinder block; these are still described as vee engines, although they may be described as having either two or one cylinder bank. In a radial engine, cylinders are arranged radially in a circle. Simple radials use one row of cylinders. Larger radials use two rows, or four. Most radials are air-cooled with separate cylinders and so there are no banks as such.
Most radials have odd numbers of cylinders in each row and stagger these between successive rows, for better cooling. A few rare radial engines, such as the Armstrong Siddeley Deerhound and the Zvezda M503 have arranged their multiple rows so as to align their cylinders into banks
The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, is called a "star engine" in some languages; the radial configuration was used for aircraft engines before gas turbine engines became predominant. Since the axes of the cylinders are coplanar, the connecting rods cannot all be directly attached to the crankshaft unless mechanically complex forked connecting rods are used, none of which have been successful. Instead, the pistons are connected to the crankshaft with a master-and-articulating-rod assembly. One piston, the uppermost one in the animation, has a master rod with a direct attachment to the crankshaft; the remaining pistons pin their connecting rods' attachments to rings around the edge of the master rod. Extra "rows" of radial cylinders can be added in order to increase the capacity of the engine without adding to its diameter.
Four-stroke radials have an odd number of cylinders per row, so that a consistent every-other-piston firing order can be maintained, providing smooth operation. For example, on a five-cylinder engine the firing order is 1, 3, 5, 2, 4, back to cylinder 1. Moreover, this always leaves a one-piston gap between the piston on its combustion stroke and the piston on compression; the active stroke directly helps compress the next cylinder to fire. If an number of cylinders were used, an timed firing cycle would not be feasible; the prototype radial Zoche aero-diesels have an number of cylinders, either four or eight. The radial engine uses fewer cam lobes than other types; as with most four-strokes, the crankshaft takes two revolutions to complete the four strokes of each piston. The camshaft ring is geared to spin slower and in the opposite direction to the crankshaft; the cam lobes exhaust. For example, four cam lobes serve all five cylinders, whereas 10 would be required for a typical inline engine with the same number of cylinders and valves.
Most radial engines use overhead poppet valves driven by pushrods and lifters on a cam plate, concentric with the crankshaft, with a few smaller radials, like the Kinner B-5 and Russian Shvetsov M-11, using individual camshafts within the crankcase for each cylinder. A few engines use sleeve valves such as the 14-cylinder Bristol Hercules and the 18-cylinder Bristol Centaurus, which are quieter and smoother running but require much tighter manufacturing tolerances. C. M. Manly constructed a water-cooled five-cylinder radial engine in 1901, a conversion of one of Stephen Balzer's rotary engines, for Langley's Aerodrome aircraft. Manly's engine produced 52 hp at 950 rpm. In 1903–1904 Jacob Ellehammer used his experience constructing motorcycles to build the world's first air-cooled radial engine, a three-cylinder engine which he used as the basis for a more powerful five-cylinder model in 1907; this was made a number of short free-flight hops. Another early radial engine was the three-cylinder Anzani built as a W3 "fan" configuration, one of which powered Louis Blériot's Blériot XI across the English Channel.
Before 1914, Alessandro Anzani had developed radial engines ranging from 3 cylinders — early enough to have been used on a few French-built examples of the famous Blériot XI from the original Blériot factory — to a massive 20-cylinder engine of 200 hp, with its cylinders arranged in four rows of five cylinders apiece. Most radial engines are air-cooled, but one of the most successful of the early radial engines was the Salmson 9Z series of nine-cylinder water-cooled radial engines that were produced in large numbers during the First World War. Georges Canton and Pierre Unné patented the original engine design in 1909, offering it to the Salmson company. From 1909 to 1919 the radial engine was overshadowed by its close relative, the rotary engine, which differed from the so-called "stationary" radial in that the crankcase and cylinders revolved with the propeller, it was similar in concept to the radial, the main difference being that the propeller was bolted to the engine, the crankshaft to the airframe.
The problem of the cooling of the cylinders, a major factor with the early "stationary" radials, was alleviated by the engine generating its own cooling airflow. In World War I many French and other Allied aircraft flew with Gnome, Le Rhône, Bentley rotary engines, the ultimate examples of which reached 250 hp although none of those over 160 hp were successful. By 1917 rotary engine development was lagging behind new inline and V-type engines, which by 1918 were producing as much as 400 hp, were powering all of the new French and British combat aircraft. Most German aircraft of the time used water-cooled inline 6-cylinder engines. Motorenfabrik Oberursel made licensed copies of the Gnome and Le Rhône rotary powerplants, Siemens-Halske built their own designs, including the Siemens-Halske Sh. III eleven-cylinder rotary engine, unusual for the period in being geared through a bevel geartrain in the rear end of the crankcase without the crankshaft being mounted to the aircraft's airframe, so that the engine's internal working components (fully in
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
A blow-off valve, dump valve or compressor bypass valve, is a pressure release system present in most turbocharged engines. Its main purpose is to take the strain off the turbo when the throttle is released. A compressor bypass valve known as a pressure relief valve or diverter valve, is a manifold vacuum-actuated valve designed to release pressure in the intake system of a turbocharged vehicle when the throttle is lifted or closed; this air pressure is re-circulated back into the non-pressurized end of the intake but after the mass airflow sensor. A blowoff valve, performs the same task but releases the air into the atmosphere instead of recirculating it; this type of valve is an aftermarket modification. The blowoff action produces a range of distinctive hissing sounds, depending on the exit design; some blowoff valves are sold with a trumpet-shaped exit. Some turbocharged vehicle owners may purchase a blowoff valve for the auditory effect when the function is not required by normal engine operation.
Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere. Blowoff valves are used to prevent compressor surge, a phenomenon that occurs when lifting off the throttle of an unvented, turbocharged engine; the sound produced is called turbo flutter. When the throttle plate on a turbocharged engine closes, with the turbine spinning at high speed, the flow reduces beyond the surge line of the compressor. At this point the delta-P across the compressor reduces leading to a collapse in flow and even flow reversal and a collapse in plenum pressure; as the compressor is still spinning at high speed, once the flow has reduced sufficiently, delta-P across the compressor begins to rise and flow is re-established into the plenum. This continues until once again the plenum is pressurised and flow begins to fall until the surge line is again crossed and the cycle repeats; this unstable flow leads to the cyclic noise sometimes heard on high boost engines with no bypass valve.
With a valve fitted, flow is maintained preventing the compressor entering the stall/surge cycle. The repeated, high speed cycling will cause a cyclic torque on the compressor and may lead to increased stresses on the bearings and compressor impeller. A blowoff valve is connected by a vacuum hose to the intake manifold after the throttle plate; when the throttle is closed, the relative manifold pressure drops below atmospheric pressure and the resulting pressure differential operates the blowoff valve's piston. The excess pressure from the turbocharger is vented into the atmosphere or recirculated into the intake upstream of the compressor inlet. In the case where a mass airflow sensor is used and is located upstream from the blowoff valve, the engine control unit will inject excess fuel because the atmospherically vented air is not subtracted from the intake charge measurements; the engine briefly operates with a fuel-rich mixture after each valve actuation. The rich mixing can lead to hesitation or stalling of the engine when the throttle is closed, a situation that worsens with higher boost pressures.
Occasional events of this type may be only a nuisance, but frequent events can foul the spark plugs and destroy the catalytic converter, as the inefficiently combusted fuel produces soot and unburned fuel in the exhaust flow can produce soot in the converter and drive the converter beyond its normal operating temperature range. An alternative method for utilizing both a MAF and a blowoff valve is to have the MAF located down stream between the intercooler and the throttle plate; this is known as Blow-through rather than the traditional Draw-through set up. Care must be taken as to the position of the MAF to prevent damage to the sensitive element. For example, on a SR20DET engine, the MAF must be at least 12 inches from the throttle plate, the blowoff valve must be 6 inches from the MAF sensor. By using a blow-through method, the MAF won't be affected by the blowoff valve opening as the pressure is vented before the air reaches the MAF. One approach used to mitigate the problem has been to reduce the boost pressure, which reduces the required venting volume and yields less charge over-calculation by the ECU.
The air can be recirculated back into the intake, a typical stock setup for cars with an upstream MAF sensor. The situation can be corrected by switching the fuel metering system over to a manifold absolute pressure sensor, a conversion that requires a compatible aftermarket ECU or piggy-back fuel controller; the MAP sensor monitors the absolute pressure in the manifold at all times and will detect the change that occurs when the valve vents, allowing the ECU to reduce fuel metering accordingly. Wastegate Water hammer
Crankcase ventilation system
In an internal combustion engine, a crankcase ventilation system is a one way, pressure-sensitive passage which allows the natural build up of gases to escape from the crankcase in a controlled manner. Blow-by, as it is called, is the result of combustion material from the combustion chamber "blowing" past the piston rings and into the rotating assembly's housing. Turbocharged engines are additionally complicated by exhaust leakage from the turbocharger shaft, in some cases, the valve stem seals; these blow-by gases, if not ventilated condense and combine with the oil vapor present in the crankcase, forming sludge or causing the oil to become diluted with unburnt fuel. Excessive crankcase pressure can furthermore lead to engine oil leaks past the crankshaft seals and other engine seals and gaskets. Therefore, it becomes imperative; this allows the blow-by gases to be vented through a PCV valve out of the crankcase. Ventilation leads to the intake manifold, allowing the gases to be recirculated before exiting through the tail pipe.
This method reduces emissions and is known as a closed-loop CVS. Conversely, an open-loop CVS vents directly to the atmosphere through a filter. From the late 19th century through the early 20th, blow-by gases from internal combustion were allowed to find their own way out to the atmosphere past seals and gaskets, it was considered normal for oil to be found both inside and outside an engine, for oil to drip to the ground in small but constant amounts. The latter had been true for steam engines and steam locomotives in the decades before. Bearing and valve designs made little to no provision for keeping oil or waste gases contained. Sealed bearings and valve covers were for special applications only. Gaskets and shaft seals were meant to limit loss of oil, but they were not expected to prevent it. On internal combustion engines, the hydrocarbon-rich blow-by gases would diffuse through the oil in the seals and gaskets into the atmosphere. Engines with high amounts of blow-by would leak profusely via those routes.
The first refinement in crankcase ventilation was the road draft tube, a pipe running from a high location contiguous to the crankcase down to an open end facing down and located in the vehicle's slipstream. When the vehicle is moving, airflow across the open end of the tube creates a draft that pulls gases out of the crankcase; the high location of the engine end of the pipe minimises liquid oil loss. An air inlet path to the crankcase, called the breather and incorporated into the oil filler cap, meant that when a draft was generated at the tube, fresh air swept through the crankcase to clear out the blow-by gases; the road draft tube, though simple, has shortcomings: it does not function when the vehicle is moving too to create a draft, so postal and other slow-moving delivery vehicles tended to suffer rapid buildup of engine sludge due to poor crankcase ventilation. And non-road vehicles such as boats never generated a draft on the tube, no matter how fast they were going. To remedy this situation manufacturers located the breather air filter in the air stream coming from the engine radiator fan, the manufacturers modified the breather to incorporate an air scoop to direct the air into the breather filter so that the engine could be ventilated while the car or truck was standing still.
The draft tube discharged the crankcase gases, composed of unburnt hydrocarbons, directly into the air. This created pollution as well as objectionable odors. Moreover, the draft tube could become clogged with snow or ice, in which case crankcase pressure would build and cause oil leaks and gasket failure. During World War II a different type of crankcase ventilation had to be invented to allow tank engines to operate during deep fording operations, where the normal draft tube ventilator would have allowed water to enter the crankcase and destroy the engine; the PCV system and its control valve were invented to meet this need, but no need for it on automobiles was recognized. In 1952, Professor A. J. Haagen-Smit, of the California Institute of Technology at Pasadena, postulated that unburned hydrocarbons were a primary constituent of smog, that gasoline-powered automobiles were a major source of those hydrocarbons; the GM Research Laboratory discovered in 1958 that the road draft tube was a major source—about half—of the hydrocarbons coming from the automobile.
The PCV system thus became. Positive crankcase ventilation was first factory-installed on a widespread basis by law on all new 1961-model cars first sold in California; the following year, New York required it. By 1964, most new cars sold in the U. S. were so equipped by voluntary industry action so as not to have to make multiple state-specific versions of vehicles. PCV became standard equipment on all vehicles worldwide because of its benefits not only in emissions reduction but in engine internal cleanliness and oil lifespan. In 1967, several years after its introduction into production, the PCV system became the subject of a U. S. federal grand jury investigation, when it was alleged by some industry critics that the Automobile Manufacturers Association was conspiring to keep several such smog reduction devices on the shelf to delay additional smog control. After eighteen months of investigation by U. S. Attorney Samuel Flatow, the grand jury returned a "no-bill" decision, clearing the AMA, but resulting in a consent decree that all U.
S. automobile companies agreed not to