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80-502: Digifant is the outgrowth of the Digijet fuel injection system first used on water-cooled Volkswagen A2 platform -based models. Digifant was introduced in 1986 on the 2.1  litre Volkswagen Type 2 (T3) ( Vanagon in the US) engine. This system combined digital fuel control as used in the earlier Digijet systems with a new map controlled digital ignition system . Subsequently, Digifant II

160-405: A hot-bulb engine used a 'jerk pump' to dispense fuel oil at high pressure to an injector. Another development in early diesel engines was the pre-combustion chamber, which was invented in 1919 by Prosper l'Orange to avoid the drawbacks of air-blast injection systems. The pre-combustion chamber made it feasible to produce engines in size suitable for automobiles and MAN Truck & Bus presented

240-610: A spark plug . The Cummins Model H diesel truck engine was introduced in America in 1933. In 1936, the Mercedes-Benz OM 138 diesel engine (using a precombustion chamber) became one of the first fuel-injected engines used in a mass-production passenger car. During World War II , several petrol engines for aircraft used direct-injection systems, such as the European Junkers Jumo 210 , Daimler-Benz DB 601 , BMW 801 , and

320-451: A carburettor. Many of the carburettor's supporting components—such as the air filter, intake manifold, and fuel line routing—could be used with few or no changes. This postponed the redesign and tooling costs of these components. Single-point injection was used extensively on American-made passenger cars and light trucks during 1980–1995, and in some European cars in the early and mid-1990s. In the US,

400-581: A central injector instead of multiple injectors. Single-point injection (also called 'throttle-body injection') uses one injector in a throttle body mounted similarly to a carburettor on an intake manifold . As in a carburetted induction system, the fuel is mixed with the air before entering the intake manifold. Single-point injection was a relatively low-cost way for automakers to reduce exhaust emissions to comply with tightening regulations while providing better "driveability" (easy starting, smooth running, no engine stuttering) than could be obtained with

480-572: A fuel injection system are described in the following sections. In some systems, a single component performs multiple functions. Fuel injection is operated by spraying pressurised fuel into the engine. Therefore a device to pressurise the fuel is needed, such as a fuel pump. The system must determine the appropriate amount of fuel to be supplied and control the fuel flow to supply this amount. Several early mechanical injection systems used relatively sophisticated helix-controlled injection pump(s) that both metered fuel and created injection pressure. Since

560-705: A fuel injection system in 1941 and by 1956 it was used in the Jaguar racing cars. At the 1957 24 Hours of Le Mans , the 1st to 4th placed cars were Jaguar D-Type entries using a Lucas fuel injection system. Also in 1957, General Motors introduced the Rochester Ramjet option, consisting of a fuel injection system for the V8 engine in the Chevrolet Corvette. During the 1960s, fuel injection systems were also produced by Hilborn , SPICA and Kugelfischer . Up until this time,

640-536: A hammer. It was further investigated and described by Harry Ricardo during experiments carried out between 1916 and 1919 to discover the reason for failures in aircraft engines . Under ideal conditions the common internal combustion engine burns the fuel/air mixture in the cylinder in an orderly and controlled fashion. The combustion is started by the spark plug some 10 to 40 crankshaft degrees prior to top dead center (TDC), depending on many factors including engine speed and load. This ignition advance allows time for

720-458: A high thermal efficiency . Since the onset of knock is sensitive to the in-cylinder pressure, temperature and autoignition chemistry associated with the local mixture compositions within the combustion chamber, simulations which account for all of these aspects have thus proven most effective in determining knock operating limits and enabling engineers to determine the most appropriate operating strategy. The objective of knock control strategies

800-405: A more complete mixing of fuel and air. Diesels actually do not suffer exactly the same "knock" as gasoline engines since the cause is known to be only the very fast rate of pressure rise, not unstable combustion. Diesel fuels are actually very prone to knock in gasoline engines but in the diesel engine there is no time for knock to occur because the fuel is only oxidized during the expansion cycle. In

880-573: A passenger car was released the following year, in the Mercedes-Benz 300SL sports car. However the engine suffered lubrication problems due to petrol diluting the engine oil, and subsequent Mercedes-Benz engines switched to a manifold injection design. Likewise, most petrol injection systems prior to the 2000s used the less-expensive manifold injection design. Throughout the 1950s, several manufacturers introduced their manifold injection systems for petrol engines. Lucas Industries had begun developing

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960-477: A pulsed flow system which used an air flow meter to calculate the amount of fuel required. L-Jetronic was widely adopted on European cars during the 1970s and 1980s. As a system that uses electronically-controlled fuel injectors which open and close to control the amount of fuel entering the engine, the L-Jetronic system uses the same basic principles as modern electronic fuel injection (EFI) systems. Prior to 1979,

1040-399: A sophisticated common-rail injection system. The latter is the most common system in modern automotive engines. During the 20th century, most petrol engines used either a carburettor or indirect fuel injection. Use of direct injection in petrol engines has become increasingly common in the 21st century. In a common rail system, fuel from the fuel tank is supplied to a common header (called

1120-470: A throttle plate potentiometer to track throttle plate position in place of the idle and full throttle switches used on earlier systems. Another characteristic of Digifant II equipped vehicles in California is a switch mount on the dashboard which has a "Check Engine" symbol. Digifant I models in California feature a Check Engine light, with the display of codes done by a special Volkswagen tool under

1200-432: Is a short lag between the fuel being injected and combustion starting. By this time there is already a quantity of fuel in the combustion chamber which will ignite first in areas of greater oxygen density prior to the combustion of the complete charge. This sudden increase in pressure and temperature causes the distinctive diesel 'knock' or 'clatter', some of which must be allowed for in the engine design. Careful design of

1280-452: Is actually more efficient than deflagration, but is usually avoided due to its damaging effects on engine components.) If detonation is allowed to persist under extreme conditions or over many engine cycles, engine parts can be damaged or destroyed. The simplest deleterious effects are typically particle wear caused by moderate knocking, which may further ensue through the engine's oil system and cause wear on other parts before being trapped by

1360-413: Is always intermittent (either sequential or cylinder-individual). This can be done either with a blast of air or hydraulically, with the latter method being more common in automotive engines. Typically, hydraulic direct injection systems spray fuel into the air inside the cylinder or combustion chamber. Direct injection can be achieved with a conventional helix-controlled injection pump, unit injectors, or

1440-546: Is called a manifold injection system. There exist two types of manifold injection systems: multi-point injection (or port injection) and single-point injection (or throttle body injection). Internal mixture formation systems can be separated into several different varieties of direct and indirect injection, the most common being the common-rail injection system, a variety of direct injection. The term "electronic fuel injection" refers to any fuel injection system controlled by an engine control unit . The fundamental functions of

1520-418: Is controlled by a vacuum -operated mechanical carbon canister control valve . Fuel pressure is maintained by a vacuum operated mechanical fuel pressure regulator on the fuel injector rail assembly . Inputs and outputs are shown in the following illustration. Digifant II as used on Golf and Jetta vehicles provides the basis for this chart. In North America , Volkswagen released two other versions of

1600-437: Is due to the travel of the flame front through the combustible fuel–air mix itself, and due to Rayleigh–Taylor instability (resulting from the hot, low-density combustion gasses expanding into the relatively cold and dense unburnt fuel–air mix) which rapidly stretches the burning zone into a complex of fingers of burning gas that have a much greater surface area than a simple spherical ball of flame would have (this latter process

1680-408: Is enhanced and accelerated by any pre-existing turbulence in the fuel–air mixture). In normal combustion, this flame front moves throughout the fuel/air mixture at a rate characteristic for the particular mixture. Pressure rises smoothly to a peak, as nearly all the available fuel is consumed, then pressure falls as the piston descends. Maximum cylinder pressure is achieved a few crankshaft degrees after

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1760-499: Is in turbocharged Saab H engines , where a system called Automatic Performance Control was used to reduce boost pressure if it caused the engine to knock. Since the avoidance of knocking combustion is so important to development engineers, a variety of simulation technologies have been developed which can identify engine design or operating conditions in which knock might be expected to occur. This then enables engineers to design ways to mitigate knocking combustion whilst maintaining

1840-533: Is injected at the same time to all the cylinders; or cylinder-individual , in which the engine control unit can adjust the injection for each cylinder individually. Multi-point injection (also called 'port injection') injects fuel into the intake ports just upstream of each cylinder's intake valve , rather than at a central point within an intake manifold. Typically, multi-point injected systems use multiple fuel injectors, but some systems, such as GM's central port injection system, use tubes with poppet valves fed by

1920-441: Is less common in cold climates. As an aftermarket solution, a water injection system can be employed to reduce combustion chamber peak temperatures and thus suppress detonation. Steam (water vapor) will suppress knock even though no added cooling is supplied. Turbulence, as stated, has a very important effect on knock. Engines with good turbulence tend to knock less than engines with poor turbulence. Turbulence occurs not only while

2000-423: Is permanently monitoring the signal of one or more knock sensors (commonly piezoelectric sensor which are able to translate vibrations into an electric signal). If the characteristic pressure peak of a knocking combustion is detected the ignition timing is retarded by steps of a few degrees. If the signal normalizes indicating a controlled combustion the ignition timing is advanced again in the same fashion keeping

2080-422: Is to attempt to optimize the trade-off between protecting the engine from damaging knock events and maximizing the engine's output torque. Knock events are an independent random process. It is impossible to design knock controllers in a deterministic platform. A single time history simulation or experiment of knock control methods are not able to provide a repeatable measurement of controller's performance because of

2160-415: The Mercedes-Benz OM 138 ) became available in the late 1930s and early 1940s, being the first fuel-injected engines for passenger car use. In passenger car petrol engines, fuel injection was introduced in the early 1950s and gradually gained prevalence until it had largely replaced carburetors by the early 1990s. The primary difference between carburetion and fuel injection is that fuel injection atomizes

2240-548: The Shvetsov ASh-82FN (M-82FN) . The German direct-injection systems were based on diesel injection systems used by Bosch, Deckel, Junkers and l'Orange. By around 1943, the Rolls-Royce Merlin and Wright R-3350 had switched from traditional carburettors to fuel-injection (called "pressure carburettors" at the time), however these engines used throttle body manifold injection , rather than the direct-injection systems of

2320-511: The Volkswagen 1.4 FSI engine introduced in 2000. However, the stratified charge systems were largely no longer in use by the late 2010s, due to increased exhaust emissions of NOx gasses and particulates, along with the increased cost and complexity of the systems. Engine knocking In spark-ignition internal combustion engines , knocking (also knock , detonation , spark knock , pinging or pinking ) occurs when combustion of some of

2400-475: The Wankel engine . In a manifold injection system, air and fuel are mixed outside the combustion chamber so that a mixture of air and fuel is sucked into the engine. The main types of manifold injections systems are multi-point injection and single-point injection . These systems use either a continuous injection or an intermittent injection design. In a continuous injection system, fuel flows at all times from

2480-669: The accumulator ), and then sent through tubing to the injectors, which inject it into the combustion chamber. The accumulator has a high-pressure relief valve to maintain pressure and return the excess fuel to the fuel tank. The fuel is sprayed with the help of a nozzle that is opened and closed with a solenoid-operated needle valve . Third-generation common rail diesels use piezoelectric injectors for increased precision, with fuel pressures up to 300  MPa or 44,000  psi . The types of common-rail systems include air-guided injection and spray-guided injection . Used by diesel engines, these systems include: This injection method

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2560-416: The air/fuel mixture in the cylinder does not result from propagation of the flame front ignited by the spark plug , but when one or more pockets of air/fuel mixture explode outside the envelope of the normal combustion front. The fuel–air charge is meant to be ignited by the spark plug only, and at a precise point in the piston's stroke. Knock occurs when the peak of the combustion process no longer occurs at

2640-478: The distributor ). These primary signals are compared to a 'map', or table of values, stored in the ECU memory. The amount of fuel delivered is controlled by the duration of actuation of the fuel injector(s). This value is taken from a programme in the ECU that has 16 points for load and 16 points for speed. These 256 primary values are then modified by coolant temperature , intake air temperature, oxygen content of

2720-454: The earth/ground on and off to control duration. All injectors operate at the same time (simultaneously, rather than sequentially) each crankshaft revolution; two complete revolutions being needed for each cylinder to receive the correct amount of fuel for each combustion cycle. Ignition system control is also digital electronic. The sensors that supply the engine load and engine speed signals for injector duration provide information about

2800-469: The flame front is subjected to a combination of heat and pressure for a certain duration (beyond the delay period of the fuel used), detonation may occur. Detonation is characterized by an almost instantaneous, explosive ignition of at least one pocket of fuel/air mixture outside of the flame front. A local shockwave is created around each pocket, and the cylinder pressure will rise sharply – and possibly beyond its design limits – causing damage. (Detonation

2880-437: The throttle body . Fuel injectors which also control the metering are called "injection valves", while injectors that perform all three functions are called unit injectors . Direct injection means that the fuel is injected into the main combustion chamber of each cylinder. The air and fuel are mixed only inside the combustion chamber. Therefore, only air is sucked into the engine during the intake stroke. The injection scheme

2960-549: The 1950 Goliath GP700 small saloon, it was also added to the Gutbrod Superior engine in 1952. This mechanically-controlled system was essentially a specially lubricated high-pressure diesel direct-injection pump of the type that is governed by the vacuum behind an intake throttle valve. A Bosch mechanical direct-injection system was also used in the straight-eight used in the 1954 Mercedes-Benz W196 Formula One racing car. The first four-stroke direct-injection petrol engine for

3040-428: The 1954-1959 Mercedes-Benz 300 SL - all used manifold injection (i.e. the injectors located at the intake ports or throttle body, instead of inside the combustion chamber). This began to change when the first mass-produced petrol direct injection system for passenger cars was a common rail system introduced in the 1997 Mitsubishi 6G74 V6 engine. The first common-rail system for a passenger car diesel engine

3120-452: The 1980s, electronic systems have been used to control the metering of fuel. More recent systems use an electronic engine control unit which meters the fuel, controls the ignition timing and controls various other engine functions. The fuel injector is effectively a spray nozzle that performs the final stage in the delivery of fuel into the engine. The injector is located in the combustion chamber , inlet manifold or - less commonly -

3200-527: The Digifant fuel injection system (in addition to standard Digifant II described above). A limited number of 1987-1990 California Golf and Jetta models are equipped with Digifant II that features an on-board diagnostics system (OBD). These vehicles have 'blink code' capacity to store up to five Diagnostic Trouble Codes (DTCs). Diagnostic troubleshooting is done by pressing the Check Engine switch on

3280-724: The ECU tends to earth/ground elsewhere, causing a specific trace to burn out on the circuit board and killing the ECU. This causes the injectors to stay open constantly, flooding the engine. Fuel injection Fuel injection is the introduction of fuel in an internal combustion engine , most commonly automotive engines , by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines. All compression-ignition engines (e.g. diesel engines ), and many spark-ignition engines (i.e. petrol (gasoline) engines , such as Otto or Wankel ), use fuel injection of one kind or another. Mass-produced diesel engines for passenger cars (such as

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3360-571: The Electrojector system, becoming the first cars known to use an electronic fuel injection (EFI) system. The Electrojector patents were subsequently sold to Bosch, who developed the Electrojector into the Bosch D-Jetronic . The D-Jetronic was produced from 1967-1976 and first used on the VW 1600TL/E . The system was a speed/density system, using engine speed and intake manifold air density to calculate

3440-497: The G10 engine in the 2000 Chevrolet Metro became the last engine available on an American-sold vehicle to use throttle body injection. In indirect-injected diesel engines (as well as Akroyd engines), there are two combustion chambers: the main combustion chamber, and a pre-chamber (also called an ante-chamber) that is connected to the main one. The fuel is injected only into the pre-chamber (where it begins to combust), and not directly into

3520-600: The German engines. From 1940, the Mitsubishi Kinsei 60 series engine used a direct-injection system, along with the related Mitsubishi Kasei engine from 1941. In 1943, a low-pressure fuel injection system was added to the Nakajima Homare Model 23 radial engine. The first mass-produced petrol direct-injection system was developed by Bosch and initially used in small automotive two-stroke petrol engines. Introduced in

3600-571: The amount of fuel to be injected. In 1974, Bosch introduced the K-Jetronic system, which used a continuous flow of fuel from the injectors (rather than the pulsed flow of the D-Jetronic system). K-Jetronic was a mechanical injection system, using a plunger actuated by the intake manifold pressure which then controlled the fuel flow to the injectors. Also in 1974, Bosch introduced the L-Jetronic system,

3680-512: The basic ignition timing point. The signal sent to the Ignition Control Unit (if not integrated into the ECU) is derived from a programme in the ECU that is similar to the injector duration programme. Engine knock control is used to allow the ignition timing to continually approach the point of detonation . This is the point where the engine will produce the most motive power , as well as

3760-671: The bypass valve. Idle speed stabilisation is enhanced by a process known as Idle Speed Control (ISC). This function (previously known as Digital Idle Stabilization), allows the ECU to modify ignition timing at idle to further improve idle quality. The 25 pin electronic control unit used in the Golf and Jetta receives inputs from the following sources: Additional signals used as inputs are: The Anti-lock Braking System (ABS), three-speed automatic transmission , and vehicle speed sensor are not linked to this system. Outputs controlling engine operation include: The evaporative emission system

3840-403: The combustion process to develop peak pressure at the ideal time for maximum recovery of work from the expanding gases. The spark across the spark plug's electrodes forms a small kernel of flame approximately the size of the spark plug gap. As it grows in size, its heat output increases, which allows it to grow at an accelerating rate, expanding rapidly through the combustion chamber. This growth

3920-536: The dashboard. This system can also have carbon monoxide (CO), ignition timing and idle speed adjusted to baseline values. In 1991, California Golf, Jetta, Fox, Cabriolet and Corrado vehicles were equipped with expanded OBD capabilities. This version was renamed "Digifant I". These later Digifant versions have 38-pin ECUs with Rapid Data Transfer and permanent DTC memory. All Eurovans with Digifant also have rapid data transfer and permanent DTC memory. These systems use

4000-521: The development of new engine management systems. These new system incorporated adaptive learning fuzzy logic , enhanced and expanded diagnostics, and the ability to meet total vehicle emissions standards. Fuel injection control is digitally electronic . It is based on the measurement engine load (this signal is provided by the Air Flow Sensor), and on engine speed (signal provided by the Hall sender in

4080-564: The diesel engine, but also improved it. He increased the air blast pressure from 4–5 kp/cm (390–490 kPa) to 65 kp/cm (6,400 kPa). In the meantime, the first manifold injection system was designed by Johannes Spiel in 1884, while working at Hallesche Maschinenfabrik in Germany. In 1891, the British Herbert-Akroyd oil engine became the first engine to use a pressurised fuel injection system. This design, called

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4160-493: The early Digifant systems suffered poor service reputations. Most of driveability issues can be traced back to a few issues: The engine coolant temperature sensor is located in the coolant flange,(under the distributor on the Polo Fox Coupe) on the front of the cylinder head (on transverse-engine vehicles). The bad earth/ground can be traced to an essential ground strap on the front upper transmission bolt. Without this,

4240-411: The electronics in fuel injection systems used analogue electronics for the control system. The Bosch Motronic multi-point fuel injection system (also amongst the first systems where the ignition system is controlled by the same device as the fuel injection system) was the first mass-produced system to use digital electronics . The Ford EEC-III single-point fuel injection system, introduced in 1980,

4320-439: The engine at its best possible operating point - the so-called ″knock limit″. Modern knock control-loop systems are able to adjust ignition timings for every cylinder individually. Depending on the specific engine the boost pressure is regulated simultaneously. This way performance is kept at its optimum while mostly eliminating the risk of engine damage caused by knock (e.g. when running on low octane fuel). An early example of this

4400-435: The engine is inhaling but also when the mixture is compressed and burned. Many pistons are designed to use "squish" turbulence to violently mix the air and fuel together as they are ignited and burned, which reduces knock greatly by speeding up burning and cooling the unburnt mixture. One example of this is all modern side valve or flathead engines . A considerable portion of the head space is made to come in close proximity to

4480-442: The engine's combustion chambers and cooling system as well as controlling the initial air intake temperature. The addition of tetraethyl lead (TEL), a soluble organolead compound added to gasoline, was common until it was discontinued for reasons of toxic pollution. Lead dust added to the intake charge will also reduce knock with various hydrocarbon fuels. Manganese compounds are also used to reduce knock with petrol fuel. Knock

4560-429: The exhaust, car battery voltage and throttle position - to provide 65,000 possible injector duration points. Digifant is unlike the earlier CIS and CIS-E fuel injection systems that it replaced, in that fuel injectors are mounted on a common fuel rail . CIS fuel injection systems used mechanical fuel injectors. The fuel injectors are wired in parallel , and are supplied with Constant System Voltage. The ECU switches

4640-441: The first direct-injected diesel engine for trucks in 1924. Higher pressure diesel injection pumps were introduced by Bosch in 1927. In 1898, German company Deutz AG started producing four-stroke petrol stationary engines with manifold injection. The 1906 Antoinette 8V aircraft engine (the world's first V8 engine) was another early four-stroke engine that used manifold injection. The first petrol engine with direct-injection

4720-429: The first generation of newly developed digital signal processing circuits. Production changes and updates were made to keep the system current with the changing California and federal emissions requirements. Updates were also made to allow integration of other vehicle systems into the scope of engine operation. Changes in circuit technology, design and processing speed along with evolving emissions standards, resulted in

4800-631: The fuel injection systems had used a mechanical control system. In 1957, the American Bendix Electrojector system was introduced, which used analogue electronics for the control system. The Electrojector was intended to be available for the Rambler Rebel mid-size car, however reliability problems meant that the fuel injection option was not offered. In 1958, the Chrysler 300D , DeSoto Adventurer , Dodge D-500 and Plymouth Fury offered

4880-572: The fuel injectors, but at a variable flow rate. The most common automotive continuous injection system is the Bosch K-Jetronic system, introduced in 1974 and used until the mid-1990s by various car manufacturers. Intermittent injection systems can be sequential , in which injection is timed to coincide with each cylinder's intake stroke; batched , in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke; simultaneous , in which fuel

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4960-633: The fuel through a small nozzle under high pressure, while carburetion relies on suction created by intake air accelerated through a Venturi tube to draw fuel into the airstream. The term "fuel injection" is vague and comprises various distinct systems with fundamentally different functional principles. Typically, the only thing all fuel injection systems have in common is a lack of carburetion . There are two main functional principles of mixture formation systems for internal combustion engines: internal mixture formation and external mixture formation. A fuel injection system that uses external mixture formation

5040-481: The gasoline engine the fuel is slowly oxidizing all the time while it is being compressed before the spark. This allows for changes to occur in the structure/makeup of the molecules before the very critical period of high temperature/pressure. Due to the large variation in fuel quality, atmospheric pressure and ambient temperature as well as the possibility of a malfunction, every modern combustion engine contains mechanisms to detect and prevent knocking. A control loop

5120-448: The highest efficiency. Additional functions of the ECU include operation of the fuel pump by closing the Ground for the fuel pump relay , and control of idle speed by a throttle plate bypass valve. The Idle Air Control Valve (IACV) (previously known as an Idle Air Stabiliser Valve - IASV), receives a changing milliamp signal that varies the strength of an electromagnet pulling open

5200-414: The injector pump, fuel injector, combustion chamber, piston crown and cylinder head can reduce knocking greatly, and modern engines using electronic common rail injection have very low levels of knock. Engines using indirect injection generally have lower levels of knock than direct injection engines, due to the greater dispersal of oxygen in the combustion chamber and lower injection pressures providing

5280-503: The main combustion chamber. Therefore, this principle is called indirect injection. There exist several slightly different indirect injection systems that have similar characteristics. Types of indirect injection used by diesel engines include: In 1872, George Bailey Brayton obtained a patent on an internal combustion engine that used a pneumatic fuel injection system, also invented by Brayton: air-blast injection . In 1894, Rudolf Diesel copied Brayton's air-blast injection system for

5360-455: The oil filter. Such wear gives the appearance of erosion, abrasion, or a "sandblasted" look, similar to the damage caused by hydraulic cavitation . Severe knocking can lead to catastrophic failure in the form of physical holes melted and pushed through the piston or cylinder head (i.e. rupture of the combustion chamber ), either of which depressurizes the affected cylinder and introduces large metal fragments, fuel, and combustion products into

5440-452: The oil system. Hypereutectic pistons are known to break easily from such shock waves. Detonation can be prevented by any or all of the following techniques: Because pressure and temperature are strongly linked, knock can also be attenuated by controlling peak combustion chamber temperatures by compression ratio reduction, exhaust gas recirculation , appropriate calibration of the engine's ignition timing schedule, and careful design of

5520-408: The optimum moment for the four-stroke cycle . The shock wave creates the characteristic metallic "pinging" sound, and cylinder pressure increases dramatically. Effects of engine knocking range from inconsequential to completely destructive. Knocking should not be confused with pre-ignition —they are two separate events. However, pre-ignition can be followed by knocking. The phenomenon of detonation

5600-413: The piston crown, making for much turbulence near TDC. In the early days of side valve heads this was not done and a much lower compression ratio had to be used for any given fuel. Also such engines were sensitive to ignition advance and had less power. Knocking is more or less unavoidable in diesel engines , where fuel is injected into highly compressed air towards the end of the compression stroke. There

5680-409: The piston passes TDC, so that the force applied on the piston (from the increasing pressure applied to the top surface of the piston) can give its hardest push precisely when the piston's speed and mechanical advantage on the crank shaft gives the best recovery of force from the expanding gases, thus maximizing torque transferred to the crankshaft. When unburned fuel–air mixture beyond the boundary of

5760-573: The rear-engined Volkswagen Beetle , sold only in Mexico . Lower-power versions (without a knock sensor), supercharged , and 16-valve variants were produced. Nearly exclusive to the European market, Volkswagen AG subsidiary Audi AG also used the Digifant system, namely in its 2.0 E variants of the Audi 80 and Audi 100 . Digifant is an engine management system designed originally to take advantage of

5840-432: The shift boot, or by a jumper and an LED by the home mechanic. Vehicles using engines equipped with Digifant fuel injection typically operated both efficiently and smoothly when new but suffered from a number of issues as the car aged, even by a few months. Digifant sensors & other components, especially the ECU itself, were remarkably sensitive to poor electrical grounding. Without a reliable ground signal to reference,

5920-492: The system was vulnerable to errors and malfunction. In the 1980s and 1990s many Volkswagen / Audi designs did not incorporate sufficient engine compartment grounding, and when the car's engine compartment became soiled with dirt, oil & road salts from several months / years of use, the fuel injection system would fail in often inexplicable ways. Backfiring, stalls & other poor running were all too common. Later versions were improved by providing multiple grounding paths, but

6000-424: Was a two-stroke aircraft engine designed by Otto Mader in 1916. Another early spark-ignition engine to use direct-injection was the 1925 Hesselman engine , designed by Swedish engineer Jonas Hesselman. This engine could run on a variety of fuels (such as oil, kerosene, petrol or diesel oil) and used a stratified charge principle whereby fuel is injected towards the end of the compression stroke, then ignited with

6080-407: Was another early digital fuel injection system. These and other electronic manifold injection systems (using either port injection or throttle-body injection ) became more widespread through the 1980s, and by the early 1990s they had replaced carburettors in most new petrol-engined cars sold in developed countries. The aforementioned injection systems for petrol passenger car engines - except for

6160-478: Was described in November 1914 in a letter from Lodge Brothers (spark plug manufacturers, and sons of Sir Oliver Lodge ) settling a discussion regarding the cause of "knocking" or "pinging" in motorcycles. In the letter they stated that an early ignition can give rise to the gas detonating instead of the usual expansion, and the sound that is produced by the detonation is the same as if the metal parts had been tapped with

6240-697: Was introduced, adding ECU integrated knock control and idle stabilization, while externalizing an Ignition Control Unit (ICU). Digifant as used in Volkswagen Golf and Volkswagen Jetta models simplified several functions, and added knock sensor control to the ignition system . Other versions of Digifant appeared on the Volkswagen Fox , Corrado , Volkswagen Transporter (T4) (known as the Eurovan in North America ), as well as 1993 and later production versions of

6320-449: Was previously used in many diesel engines. Types of systems include: The M-System , used in some diesel engines from the 1960s to the 1980s, sprayed the fuel onto the walls of the combustion chamber, as opposed to most other direct-injection systems which spray the fuel into the middle of the chamber. Manifold injection systems are common in petrol-fuelled engines such as the Otto engine and

6400-466: Was the Fiat Multijet straight-four engine, introduced in the 1999 Alfa Romeo 156 1.9 JTD model. Since the 2010s, many petrol engines have switched to direct-injection (sometimes in combination with separate manifold injectors for each cylinder). Similarly, many modern diesel engines use a common-rail design. Stratified charge injection was used in several petrol engines in the early 2000s, such as

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