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An ignition system generates a spark or heats an electrode to a high temperature to ignite a fuel-air mixture in spark ignition
internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combus ...
s, oil-fired and gas-fired
boiler A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central h ...
s,
rocket engines A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordanc ...
, etc. The widest application for spark ignition internal combustion engines is in petrol (gasoline) road vehicles such as cars and motorcycles. Compression ignition Diesel engines ignite the fuel-air mixture by the heat of compression and do not need a spark. They usually have
glowplug A glowplug (alternatively spelled as glow plug or glow-plug) is a heating device used to aid in starting diesel engines. In cold weather, high-speed diesel engines can be difficult to start because the mass of the cylinder block and cylinder he ...
s that preheat the
combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...
to allow starting in cold weather. Other engines may use a flame, or a heated tube, for ignition. While this was common for very early engines it is now rare. The first
electric spark An electric spark is an abrupt electrical discharge that occurs when a sufficiently high electric field creates an ionized, electrically conductive channel through a normally-insulating medium, often air or other gases or gas mixtures. Michael F ...
ignition was probably
Alessandro Volta Alessandro Giuseppe Antonio Anastasio Volta (, ; 18 February 1745 – 5 March 1827) was an Italian physicist, chemist and lay Catholic who was a pioneer of electricity and power who is credited as the inventor of the electric battery and the ...
's toy electric pistol from the 1780s.
Siegfried Marcus Siegfried Samuel Marcus (; 18 September 1831 – 1 July 1898) was a German inventor. Marcus was born of Jewish descent in Malchin, in the Grand Duchy of Mecklenburg-Schwerin. He made the first petrol-powered vehicle in 1864, while living ...
patented his "Electrical igniting device for gas engines" on 7 October 1884.


History


Magneto systems

The simplest form of spark ignition is that using a
magneto A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...
. The engine spins a
magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
inside a coil, or, in the earlier designs, a coil inside a fixed magnet, and also operates a
contact breaker A contact breaker (or "points") is a type of electrical switch, found in the ignition systems of spark-ignition internal combustion engines. The switch is automatically operated by a cam driven by the engine. The timing of operation of the switch ...
, interrupting the current and causing the voltage to be increased sufficiently to jump a small gap. The
spark plug A spark plug (sometimes, in British English, a sparking plug, and, colloquially, a plug) is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air ...
s are connected directly from the
magneto A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...
output. Early magnetos had one coil, with the contact breaker (sparking plug) inside the combustion chamber. In about 1902, Bosch introduced a double-coil magneto, with a fixed sparking plug, and the contact breaker outside the cylinder. Magnetos are not used in modern cars, but because they generate their own electricity they are often found on small engines such as those found in
moped A moped ( ) is a type of small motorcycle, generally having a less stringent licensing requirement than full motorcycles or automobiles. The term used to mean a similar vehicle except with both bicycle pedals and a motorcycle engine. Mopeds typic ...
s,
lawnmower A lawn mower (also known as a mower, grass cutter or lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a grass surface to an even height. The height of the cut grass may be fixed by the design of the mower, but g ...
s,
snowblower A snow blower or snow thrower is a machine for removing snow from an area where it is problematic, such as a driveway, sidewalk, roadway, railroad track, ice rink, or runway. The commonly used term "snow blower" is a misnomer, as the snow is ...
s,
chainsaw A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, ...
s, etc. where a battery-based electrical system is not present for any combination of necessity, weight, cost, and reliability reasons. They are also used on piston-engined
aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines ...
engines. Although an electrical supply is available, magneto systems are used mainly because of their higher reliability. Magnetos were used on the small engine's ancestor, the stationary "hit and miss" engine which was used in the early twentieth century, on older gasoline or distillate farm
tractor A tractor is an engineering vehicle specifically designed to deliver a high tractive effort (or torque) at slow speeds, for the purposes of hauling a trailer or machinery such as that used in agriculture, mining or construction. Most common ...
s before battery starting and lighting became common, and on aircraft piston engines. Magnetos were used in these engines because their simplicity and self-contained operation was more reliable, and because magnetos weighed less than having a battery and
dynamo file:DynamoElectricMachinesEndViewPartlySection USP284110.png, "Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator (electric), commutator. Dynamos were the f ...
or
alternator An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Go ...
. Aircraft engines usually have dual magnetos to provide redundancy in the event of a failure, and to increase efficiency by thoroughly and quickly burning the fuel air mix from both sides towards the center. The Wright brothers used a magneto invented in 1902 and built for them in 1903 by Dayton, Ohio inventor, Vincent Groby Apple. Some older automobiles had both a magneto system and a battery actuated system (see below) running simultaneously to ensure proper ignition under all conditions with the limited performance each system provided at the time. This gave the benefits of easy starting (from the battery system) with reliable sparking at speed (from the magneto). Many modern magneto systems (except for small engines) have removed the second (high voltage) coil from the magneto itself and placed it in an external coil assembly similar to the
ignition coil An ignition coil (also called a spark coil) is an induction coil in an automobile's ignition system that transforms the battery's voltage to the thousands of volts needed to create an electric spark in the spark plugs to ignite the fuel. So ...
described below. In this development, the induced current in the coil in the magneto also flows through the primary of the external coil, generating a high voltage in the secondary as a result. Such a system is referred to as an 'energy transfer system'. Energy transfer systems provide the ultimate in ignition reliability.


Switchable systems

The output of a magneto depends on the speed of the engine, and therefore starting can be problematic. Some magnetos include an impulse system, which spins the magnet quickly at the proper moment, making easier starting at slow cranking speeds. Some engines, such as aircraft but also the Ford
Model T The Ford Model T is an automobile that was produced by Ford Motor Company from October 1, 1908, to May 26, 1927. It is generally regarded as the first affordable automobile, which made car travel available to middle-class Americans. The relati ...
, used a system which relied on non rechargeable
dry cell upLine art drawing of a dry cell: 1. brass cap, 2. plastic seal, 3. expansion space, 4. porous cardboard, 5. zinc can, 6. carbon rod, 7. chemical mixture A dry cell is a type of electric battery, commonly used for portable electrical devices. Un ...
s, (similar to a large flashlight battery, and which was not maintained by a charging system as on modern automobiles) to start the engine or for starting and running at low speed. The operator would manually switch the ignition over to magneto operation for high speed operation. To provide high voltage for the spark from the low voltage batteries, a 'tickler' was used, which was essentially a larger version of the once widespread electric
buzzer A buzzer or beeper is an audio signaling device, which may be mechanical, electromechanical, or piezoelectric (''piezo'' for short). Typical uses of buzzers and beepers include alarm devices, timers, train and confirmation of user input such as a ...
. With this apparatus, the direct current passes through an
electromagnetic coil An electromagnetic coil is an electrical Electrical conductivity, conductor such as a wire in the shape of a wiktionary:coil, coil (spiral or helix). Electromagnetic coils are used in electrical engineering, in applications where electric curre ...
which pulls open a pair of contact points, interrupting the current; the
magnetic field A magnetic field is a vector field that describes the magnetic influence on moving electric charges, electric currents, and magnetic materials. A moving charge in a magnetic field experiences a force perpendicular to its own velocity and to ...
collapses, the spring-loaded points close again, the circuit is reestablished, and the cycle repeats rapidly. The rapidly collapsing magnetic field, however, induces a high voltage across the coil which can only relieve itself by arcing across the contact points; while in the case of the buzzer this is a problem as it causes the points to
oxidize Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a d ...
and/or weld together, in the case of the ignition system this becomes the source of the high voltage to operate the spark plugs. In this mode of operation, the coil would "buzz" continuously, producing a constant train of sparks. The entire apparatus was known as the 'Model T spark coil' (in contrast to the modern ignition coil which is only the actual coil component of the system). Long after the demise of the Model T as transportation they remained a popular self-contained source of high voltage for electrical home experimenters, appearing in articles in magazines such as ''
Popular Mechanics ''Popular Mechanics'' (sometimes PM or PopMech) is a magazine of popular science and technology, featuring automotive, home, outdoor, electronics, science, do-it-yourself, and technology topics. Military topics, aviation and transportation o ...
'' and projects for school
science fair Science and engineering fairs, hosted by schools worldwide, offer students the opportunity to experience the practices of science and engineering for themselves. In the United States, the Next Generation Science Standards makes experiencing the ...
s as late as the early 1960s. In the UK these devices were commonly known as
trembler coil A trembler coil, buzz coil or vibrator coil is a type of high-voltage ignition coil used in the ignition system of early automobiles, most notably the Benz Patent-Motorwagen and the Ford Model T. Its distinguishing feature is a vibrating magnetica ...
s and were popular in cars pre-1910, and also in commercial vehicles with large engines until around 1925 to ease starting. The Model T magneto (built into the
flywheel A flywheel is a mechanical device which uses the conservation of angular momentum to store rotational energy; a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, ass ...
) differed from modern implementations by not providing high voltage directly at the output; the maximum voltage produced was about 30 volts, and therefore also had to be run through the spark coil to provide high enough voltage for ignition, as described above, although the coil would not "buzz" continuously in this case, only going through one cycle per spark. In either case, the low voltage was switched to the appropriate spark plug by the timer mounted on the front of the engine. This performed the equivalent function to the modern
distributor A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
, although by directing the low voltage, not the high voltage as for the distributor. The
ignition timing In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke. The need for ...
was adjustable by rotating this mechanism through a lever mounted on the
steering column The automotive steering column is a device intended primarily for connecting the steering wheel to the steering mechanism. Secondary functions A steering column may also perform the following secondary functions: *energy dissipation management ...
. As the precise timing of the spark depends on ''both'' the 'timer' and the trembler contacts within the coil, this is less consistent than the breaker points of the later distributor. However, for the low speed and the low compression of such early engines, this imprecise timing was acceptable.


Battery and coil-operated ignition

With the universal adoption of electrical starting for automobiles, and the availability of a large
battery Battery most often refers to: * Electric battery, a device that provides electrical power * Battery (crime), a crime involving unlawful physical contact Battery may also refer to: Energy source *Automotive battery, a device to provide power t ...
to provide a constant source of electricity, magneto systems were abandoned for systems which interrupted current at battery voltage, using an ignition coil to step the voltage up to the needs of the ignition, and a
distributor A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
to route the ensuing pulse to the correct spark plug at the correct time. The
Benz Patent-Motorwagen The Benz Patent-Motorwagen ("patent motorcar"), built in 1885 by the German Carl Benz, is widely regarded as the world's first practical modern automobile and was the first car put into series production. It was patented and unveiled in 1886. T ...
and the
Ford Model T The Ford Model T is an automobile that was produced by Ford Motor Company from October 1, 1908, to May 26, 1927. It is generally regarded as the first affordable automobile, which made car travel available to middle-class Americans. The relati ...
used a
trembler coil A trembler coil, buzz coil or vibrator coil is a type of high-voltage ignition coil used in the ignition system of early automobiles, most notably the Benz Patent-Motorwagen and the Ford Model T. Its distinguishing feature is a vibrating magnetica ...
ignition system. A trembler coil was a battery-powered
induction coil An induction coil or "spark coil" (archaically known as an inductorium or Ruhmkorff coil after Heinrich Rühmkorff) is a type of electrical transformer used to produce high-voltage pulses from a low-voltage direct current (DC) supply. p.98 To ...
; the trembler interrupted the current through the coil and caused a quick series of sparks during each firing. The trembler coil would be energized at an appropriate point in the engine cycle. In the Model T, the four-cylinder engine had a trembler coil for each cylinder; a commutator (timer case) delivered power to the trembler coils. The Model T would be started on battery but then switched to an magneto. An improved ignition system was developed by the
Dayton Engineering Laboratories Co. Delco Electronics Corporation was the automotive electronics design and manufacturing subsidiary of General Motors based in Kokomo, Indiana, that manufactured ''Delco'' Automobile radios and other electric products found in GM cars. In 1972, G ...
(Delco) and introduced in the 1912
Cadillac The Cadillac Motor Car Division () is a division of the American automobile manufacturer General Motors (GM) that designs and builds luxury vehicles. Its major markets are the United States, Canada, and China. Cadillac models are distributed i ...
. This ignition was developed by
Charles Kettering Charles Franklin Kettering (August 29, 1876 – November 25, 1958) sometimes known as Charles Fredrick Kettering was an American inventor, engineer, businessman, and the holder of 186 patents. For the list of patents issued to Kettering, see, Le ...
and was a wonder in its day. It consisted of a single ignition coil, breaker points (the switch), a
capacitor A capacitor is a device that stores electrical energy in an electric field by virtue of accumulating electric charges on two close surfaces insulated from each other. It is a passive electronic component with two terminals. The effect of ...
(to prevent the points from arcing at break) and a
distributor A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
(to direct the electricity from the ignition coil to the correct cylinder). The points allow the coil magnetic field to build. When the points open by a
cam Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...
arrangement, the magnetic field collapses inducing an EMF in the primary that is much larger than the battery voltage and the
transformer A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the transformer' ...
action produces a large output voltage (20 kV or greater) from the secondary. The capacitor suppresses arcing at the points when they open; without the capacitor, the energy stored in the coil would be expended at an arc across the points rather than at the spark plug gap. The Kettering system became the primary ignition system for many years in the automotive industry due to its lower cost, and relative simplicity.


Modern ignition systems

The ignition system is typically controlled by a key operated
Ignition switch An ignition switch, starter switch or start switch is a switch in the control system of a motor vehicle that activates the main electrical systems for the vehicle, including "accessories" (radio, power windows, etc.). In vehicles powered by intern ...
.


Mechanically timed ignition

Most
four-stroke engine A four-stroke (also four-cycle) engine is an internal combustion (IC) engine in which the piston completes four separate strokes while turning the crankshaft. A stroke refers to the full travel of the piston along the cylinder, in either directio ...
s have used a mechanically timed electrical ignition system. The heart of the system is the distributor. The distributor contains a rotating
cam Calmodulin (CaM) (an abbreviation for calcium-modulated protein) is a multifunctional intermediate calcium-binding messenger protein expressed in all eukaryotic cells. It is an intracellular target of the secondary messenger Ca2+, and the bin ...
driven by the engine's drive, a set of breaker points, a condenser, a rotor and a distributor cap. External to the distributor is the ignition coil, the spark plugs and wires linking the distributor to the spark plugs and ignition coil. (see diagram Below) The system is powered by a lead-acid battery, which is charged by the car's electrical system using a
dynamo file:DynamoElectricMachinesEndViewPartlySection USP284110.png, "Dynamo Electric Machine" (end view, partly section, ) A dynamo is an electrical generator that creates direct current using a commutator (electric), commutator. Dynamos were the f ...
or
alternator An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Go ...
. The engine operates contact breaker points, which interrupt the current to an induction coil (known as the ignition coil). The ignition coil consists of two transformer windings — the primary and secondary. These windings share a common magnetic core. An alternating current in the primary induces an alternating magnetic field in the core and hence an alternating current in the secondary. The ignition coil's secondary has more turns than the primary. This is a step-up transformer, which produces a high voltage from the secondary winding. The primary winding is connected to the battery (usually through a current-limiting
ballast Ballast is material that is used to provide stability to a vehicle or structure. Ballast, other than cargo, may be placed in a vehicle, often a ship or the gondola of a balloon or airship, to provide stability. A compartment within a boat, ship, ...
resistor A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active el ...
). Inside the ignition coil one end of each winding is connected together. This common point is taken to the capacitor/contact breaker junction. The other, high voltage, end of the secondary is connected to the distributor's rotor. The ignition firing sequence begins with the points (or contact breaker) closed. A steady current flows from the battery, through the current-limiting resistor, through the primary coil, through the closed breaker points and finally back to the battery. This current produces a magnetic field within the coil's core. This magnetic field forms the energy reservoir that will be used to drive the ignition spark. As the engine crankshaft turns, it also turns the distributor shaft at half the speed. In a four-stroke engine, the crankshaft turns twice for the ignition cycle. A multi-lobed cam is attached to the distributor shaft; there is one lobe for each engine cylinder. A spring-loaded rubbing block follows the lobed portions of the cam contour and controls the opening and closing of points. During most of the cycle, the rubbing block keeps the points closed to allow a current to build in the ignition coil's primary winding. As a piston reaches the top of the engine's compression cycle, the cam's lobe is high enough to cause the breaker points to open. Opening the points causes the current through the primary coil to stop. Without the steady current through the primary, the magnetic field generated in the coil immediately collapses. This high rate of change of magnetic flux induces a high voltage in the coil's secondary windings that ultimately causes the spark plug's gap to arc and ignite the fuel. The spark generation story is a little more complicated. The purpose of the ignition coil is to make a spark that jumps the spark plug's gap, which might be (it also has to jump the rotor-to-distributor-post gap). At the moment the points open, there is a much smaller gap, say about , across the points. Something must be done to prevent the points from arcing as they separate; if the points arc, then they will drain the magnetic energy that was intended for the spark plug. The capacitor (condenser) performs that task. The capacitor temporarily keeps the primary current flowing so the voltage across the points is below the point's arcing voltage. There is a race: the voltage across the points is increasing as the primary current charges the capacitor, but at the same time the points' separation (and consequent arcing voltage) is increasing. Ultimately, the point separation will increase to something such as , the maximum separation of the points. In addition to staying below the arcing voltage, the ignition system keeps the voltage across the points below the breakdown voltage for an air gap to prevent a
glow discharge A glow discharge is a plasma formed by the passage of electric current through a gas. It is often created by applying a voltage between two electrodes in a glass tube containing a low-pressure gas. When the voltage exceeds a value called the str ...
across the points. Such a glow discharge would quickly transition to an arc, and the arc would prevent the spark plug from firing. The minimum voltage for a glow discharge in air is about 320 V. Consequently, the capacitor value is chosen to also keep the voltage across the points to be less than 320 V. Keeping the points from arcing when they separate is the reason the ignition coil includes a secondary winding rather than using just a simple
inductor An inductor, also called a coil, choke, or reactor, is a passive two-terminal electrical component that stores energy in a magnetic field when electric current flows through it. An inductor typically consists of an insulated wire wound into a c ...
. If the transformer has a 100:1 ratio, then the secondary voltage can reach 30 kV. The ignition coil's high voltage output is connected to the
rotor Rotor may refer to: Science and technology Engineering *Rotor (electric), the non-stationary part of an alternator or electric motor, operating with a stationary element so called the stator * Helicopter rotor, the rotary wing(s) of a rotorcraft ...
that sits on top of the distributor shaft. Surrounding the rotor is the
distributor cap A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plu ...
. The arrangement sequentially directs the output of the secondary winding to the appropriate spark plugs. The high voltage from the coil's secondary (typically 20,000 to 50,000 volts) causes a spark to form across the gap of the spark plug that in turn ignites the compressed air-fuel mixture within the engine. It is the creation of this spark which consumes the energy that was stored in the ignition coil's magnetic field. The flat twin cylinder 1948
Citroën 2CV The Citroën 2CV (french: link=no, deux chevaux(-vapeur), , lit. "two steam horse(power)s", meaning "two ''taxable'' horsepower") is an air-cooled front-engine, front-wheel-drive, economy family car, introduced at the 1948 Paris Mondial de l ...
used one double ended coil without a distributor, and just contact breakers, in a
wasted spark A wasted spark system is a type of ignition system used in some four-stroke cycle internal combustion engines. In a wasted spark system, the spark plugs fire in pairs, with one plug in a cylinder on its compression stroke and the other plug in a ...
system. Some two-cylinder motorcycles and motor scooters had two contact points feeding twin coils each connected directly to one of the two sparking plugs without a distributor; e.g. the BSA Thunderbolt and
Triumph Tigress The Triumph Tigress, also sold as the BSA Sunbeam, was a scooter designed to have good performance and handling for the motorcycle enthusiast. The entry of the BSA group into the scooter field was announced by Edward Turner in October 1958 ...
. High performance engines with eight or more cylinders that operate at high r.p.m. (such as those used in motor racing) demand both a higher rate of spark and a higher spark energy than the simple ignition circuit can provide. This problem is overcome by using either of these adaptations: * Two complete sets of coils, breakers and condensers can be provided - one set for each half of the engine, which is typically arranged in V-8 or V-12 configuration. Although the two ignition system halves are electrically independent, they typically share a single distributor which in this case contains two breakers driven by the rotating cam, and a rotor with two isolated conducting planes for the two high voltage inputs. * A single breaker driven by a cam and a return spring is limited in spark rate by the onset of contact bounce or float at high rpm. This limit can be overcome by substituting for the breaker a 'pair of breakers' (aka "dual points") that are connected electrically in parallel but spaced on opposite sides of the cam so they are driven out of phase. Each breaker then switches current flow at half the rate of a single breaker and the "dwell" time for current buildup in the coil is maximized since it is shared between the breakers, one contact set being the "make" pair and the second being the "break" pair. The
Lamborghini Automobili Lamborghini S.p.A. () is an Italian brand and manufacturer of luxury sports cars and SUVs based in Sant'Agata Bolognese. The company is owned by the Volkswagen Group through its subsidiary Audi. Ferruccio Lamborghini (1916–1993) ...
V-8 engine has both these adaptations and therefore uses two ignition coils and a single distributor that contains 4 contact breakers. A distributor-based system is not greatly different from a magneto system except that more separate elements are involved. There are also advantages to this arrangement. For example, the position of the contact breaker points relative to the engine angle can be changed a small amount dynamically, allowing the ignition timing to be automatically advanced with increasing
revolutions per minute Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
(RPM) or increased
manifold vacuum Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere. Manifold vacuum is an effect of a piston's movement on the induction stroke and the ...
, giving better efficiency and performance. However it is necessary to check periodically the maximum opening gap of the breaker(s), using a feeler gauge, since this mechanical adjustment affects the "dwell" time during which the coil charges, and breakers should be re-dressed or replaced when they have become pitted by electric arcing. This system was used almost universally until the 1972, when
electronic Electronic may refer to: *Electronics, the science of how to control electric energy in semiconductor * ''Electronics'' (magazine), a defunct American trade journal *Electronic storage, the storage of data using an electronic device *Electronic co ...
ignition systems started to appear.


Electronic ignition

The disadvantage of the mechanical system is the use of breaker points to interrupt the low-voltage high-current through the primary winding of the coil; the points are subject to mechanical wear where they ride the cam to open and shut, as well as oxidation and burning at the contact surfaces from the constant sparking. They require regular adjustment to compensate for wear, and the opening of the contact breakers, which is responsible for spark timing, is subject to mechanical variations. In addition, the spark voltage is also dependent on contact effectiveness, and poor sparking can lead to lower engine efficiency. A mechanical contact breaker system cannot control an average ignition current of more than about 3 A while still giving a reasonable service life, and this may limit the power of the spark and ultimate engine speed. Electronic ignition (EI) solves these problems. In the initial systems, points were still used but they handled only a low current which was used to control the high primary current through a solid state switching system. Soon, however, even these contact breaker points were replaced by an angular
sensor A sensor is a device that produces an output signal for the purpose of sensing a physical phenomenon. In the broadest definition, a sensor is a device, module, machine, or subsystem that detects events or changes in its environment and sends ...
of some kind - either
optical Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...
, where a vaned rotor breaks a light beam, or more commonly using a
Hall effect sensor A Hall effect sensor (or simply Hall sensor) is a type of sensor which detects the presence and magnitude of a magnetic field using the Hall effect. The output voltage of a Hall sensor is directly proportional to the strength of the field. ...
, which responds to a rotating
magnet A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, ...
mounted on the distributor shaft. The sensor output is shaped and processed by suitable circuitry, then used to trigger a switching device such as a
thyristor A thyristor () is a solid-state semiconductor device with four layers of alternating P- and N-type materials used for high-power applications. It acts exclusively as a bistable switch (or a latch), conducting when the gate receives a current ...
, which switches a large current through the coil. The first electronic ignition (a
cold cathode A cold cathode is a cathode that is not electrically heated by a filament.A negatively charged electrode emits electrons or is the positively charged terminal. For more, see field emission. A cathode may be considered "cold" if it emits more el ...
type) was tested in 1948 by Delco-Remy,''Super Street Cars'', 9/81, p.34. while
Lucas Lucas or LUCAS may refer to: People * Lucas (surname) * Lucas (given name) Arts and entertainment * Luca Family Singers, also known as "lucas ligner en torsk" * ''Lucas'' (album) (2007), an album by Skeletons and the Kings of All Cities * ''L ...
introduced a
transistor upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink). A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch e ...
ized ignition in 1955, which was used on
BRM British Racing Motors (BRM) was a British Formula One motor racing team. Founded in 1945 and based in the market town of Bourne in Lincolnshire, it participated from 1951 to 1977, competing in 197 grands prix and winning seventeen. BRM wo ...
and
Coventry Climax Coventry Climax was a British forklift truck, fire pump, racing, and other specialty engine manufacturer. History Pre WW1 The company was started in 1903 as Lee Stroyer, but two years later, following the departure of Stroyer, it was relocat ...
Formula One Formula One (also known as Formula 1 or F1) is the highest class of international racing for open-wheel single-seater formula racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The World Drivers' Championship, ...
engines in 1962. The aftermarket began offering EI that year, with both the AutoLite Electric Transistor 201 and
Tung-Sol Tung-Sol was an American manufacturer of electronics, mainly lamps and vacuum tubes. History Tung-Sol was founded as Tung-Sol Lamp Works Inc. in Newark, New Jersey in 1907. Their early products were mainly geared towards the automotive market ...
EI-4 (thyratron capacitive discharge) being available.''Super Street Cars'', 9/81, p.35.
Pontiac Pontiac may refer to: *Pontiac (automobile), a car brand *Pontiac (Ottawa leader) ( – 1769), a Native American war chief Places and jurisdictions Canada *Pontiac, Quebec, a municipality ** Apostolic Vicariate of Pontiac, now the Roman Catholic D ...
became the first automaker to offer an optional EI, the breakerless magnetic pulse-triggered Delcotronic, on some 1963 models; it was also available on some
Corvette A corvette is a small warship. It is traditionally the smallest class of vessel considered to be a proper (or " rated") warship. The warship class above the corvette is that of the frigate, while the class below was historically that of the slo ...
s. The first commercially available all solid-state (SCR) capacitive discharge ignition was manufactured by Hyland Electronics in Canada also in 1963.
Ford Ford commonly refers to: * Ford Motor Company, an automobile manufacturer founded by Henry Ford * Ford (crossing), a shallow crossing on a river Ford may also refer to: Ford Motor Company * Henry Ford, founder of the Ford Motor Company * Ford F ...
fitted a FORD designed breakerless system on the
Lotus 25 The Lotus 25 was a racing car designed by Colin Chapman for the 1962 Formula One season. It was a revolutionary design, the first fully stressed monocoque chassis to appear in Formula One. In the hands of Jim Clark it took 14 World Championship ...
s entered at
Indianapolis Indianapolis (), colloquially known as Indy, is the state capital and most populous city of the U.S. state of Indiana and the seat of Marion County. According to the U.S. Census Bureau, the consolidated population of Indianapolis and Marion ...
the next year, ran a fleet test in 1964, and began offering optional EI on some models in 1965. This electronic system was utilized on the GT40s campaigned by Shelby American and Holman and Moody. Robert C. Hogle, Ford Motor Company, presented the, "Mark II-GT Ignition and Electrical System", Publication #670068, at the SAE Congress, Detroit, Michigan, January 9–13, 1967. Beginning in 1958, Earl W. Meyer at Chrysler worked on EI, continuing until 1961 and resulting in use of EI on the company's
NASCAR The National Association for Stock Car Auto Racing, LLC (NASCAR) is an American auto racing sanctioning and operating company that is best known for stock car racing. The privately owned company was founded by Bill France Sr. in 1948, and hi ...
hemi Hemi may refer to: People Surname * Jack Hemi (1914–1996), New Zealand freezing worker, rugby union and league player, shearer * Ronald Hemi (1933–2000), New Zealand rugby union player Given name * Hemi Bawa, Indian painter and sculptor * H ...
s in 1963 and 1964.
Prest-O-Lite Union Carbide Corporation is an American chemical corporation wholly owned subsidiary (since February 6, 2001) by Dow Chemical Company. Union Carbide produces chemicals and polymers that undergo one or more further conversions by customers befor ...
's CD-65, which relied on capacitance discharge (CD), appeared in 1965, and had "an unprecedented 50,000 mile warranty." (This differs from the non-CD Prest-O-Lite system introduced on
AMC AMC may refer to: Film and television * AMC Theatres, an American movie theater chain * AMC Networks, an American entertainment company ** AMC (TV channel) ** AMC+, streaming service ** AMC Networks International, an entertainment company *** ...
products in 1972, and made standard equipment for the 1975 model year.) A similar CD unit was available from Delco in 1966, which was optional on
Oldsmobile Oldsmobile or formally the Oldsmobile Division of General Motors was a brand of American automobiles, produced for most of its existence by General Motors. Originally established as "Olds Motor Vehicle Company" by Ransom E. Olds in 1897, it produ ...
, Pontiac, and GMC vehicles in the 1967 model year. Also in 1967,
Motorola Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...
debuted their breakerless CD system. The most famous aftermarket electronic ignition which debuted in 1965, was the Delta Mark 10 capacitive discharge ignition, which was sold assembled or as a kit. The
Fiat Dino The Fiat Dino (Type 135) was a front-engine, rear-wheel-drive sports car produced by Fiat from 1966 to 1973. The Dino name refers to the Ferrari Dino V6 engine, produced by Fiat and installed in the cars to achieve the production numbers sufficient ...
was the first production car to come standard with EI in 1968, followed by the Jaguar XJ Series 1 in 1971, Chrysler (after a 1971 trial) in 1973 and by Ford and GM in 1975. In 1967, Prest-O-Lite made a "Black Box" ignition amplifier, intended to take the load off the distributor's breaker points during high rpm runs, which was used by
Dodge Dodge is an American brand of automobiles and a division of Stellantis, based in Auburn Hills, Michigan. Dodge vehicles have historically included performance cars, and for much of its existence Dodge was Chrysler's mid-priced brand above P ...
and
Plymouth Plymouth () is a port city and unitary authority in South West England. It is located on the south coast of Devon, approximately south-west of Exeter and south-west of London. It is bordered by Cornwall to the west and south-west. Plymouth ...
on their factory Super Stock
Coronet A coronet is a small crown consisting of ornaments fixed on a metal ring. A coronet differs from other kinds of crowns in that a coronet never has arches, and from a tiara in that a coronet completely encircles the head, while a tiara does ...
and
Belvedere Belvedere (from Italian, meaning "beautiful sight") may refer to: Places Australia *Belvedere, Queensland, a locality in the Cassowary Coast Region Africa * Belvedere (Casablanca), a neighborhood in Casablanca, Morocco *Belvedere, Harare, Zi ...
drag racer Drag racing is a type of motor racing in which automobiles or motorcycles compete, usually two at a time, to be first to cross a set finish line. The race follows a short, straight course from a standing start over a measured distance, most c ...
s. This amplifier was installed on the interior side of the cars' firewall, and had a duct which provided outside air to cool the unit. The rest of the system (distributor and spark plugs) remains as for the mechanical system. The lack of moving parts compared with the mechanical system leads to greater reliability and longer service intervals. Chrysler introduced breakerless ignition in mid-1971 as an option for its 340 V8 and the 426 Street Hemi. For the 1972 model year, the system became standard on its high-performance engines (the and the four-barrel
carburetor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...
-equipped ) and was an option on its , , two-barrel , and low-performance . Breakerless ignition was standardised across the model range for 1973. For older cars, it is usually possible to
retrofit Retrofitting is the addition of new technology or features to older systems. Retrofits can happen for a number of reasons, for example with big capital expenditures like naval vessels, military equipment or manufacturing plants, businesses or go ...
an EI system in place of the mechanical one. In some cases, a modern distributor will fit into the older engine with no other modifications, like the H.E.I. distributor made by
General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
, the Hot-Spark electronic ignition conversion kit, and the Chrysler breakerless system. Other innovations are currently available on various cars. In some models, rather than one central coil, there are individual coils on each spark plug, sometimes known as
direct ignition A distributor is an enclosed rotating switch used in spark-ignition internal combustion engines that have mechanically timed ignition. The distributor's main function is to route high voltage current from the ignition coil to the spark plugs ...
or coil on plug (COP). This allows the coil a longer time to accumulate a charge between sparks, and therefore a higher energy spark. A variation on this has each coil handle two plugs, on cylinders which are 360 degrees out of phase (and therefore reach
top dead center In a reciprocating engine, the dead centre is the position of a piston in which it is either farthest from, or nearest to, the crankshaft. The former is known as Top Dead Centre (TDC) while the latter is known as Bottom Dead Centre (BDC). ...
(TDC) at the same time); in the four-cycle engine this means that one plug will be sparking during the end of the exhaust stroke while the other fires at the usual time, a so-called "
wasted spark A wasted spark system is a type of ignition system used in some four-stroke cycle internal combustion engines. In a wasted spark system, the spark plugs fire in pairs, with one plug in a cylinder on its compression stroke and the other plug in a ...
" arrangement which has no drawbacks apart from faster spark plug erosion; the paired cylinders are 1/4 and 2/3 on four cylinder arrangements, 1/4, 6/3, 2/5 on six cylinder engines and 6/7, 4/1, 8/3 and 2/5 on V8 engines.northstarperformance.comfixya.comi.fixya.net
/ref> Other systems do away with the distributor as a timing apparatus and use a magnetic crank angle sensor mounted on the crankshaft to trigger the ignition at the proper time.


Digital electronic ignitions

At the turn of the 21st century digital electronic ignition modules became available for small engines on such applications as
chainsaw A chainsaw (or chain saw) is a portable gasoline-, electric-, or battery-powered saw that cuts with a set of teeth attached to a rotating chain driven along a guide bar. It is used in activities such as tree felling, limbing, bucking, pruning, ...
s,
string trimmer A string trimmer, also known by the portmanteau strimmer and the trademarks Weedwacker, Weed eater and Whipper Snipper. is a garden tool for cutting grass, small weeds, and groundcover. It uses a whirling monofilament line instead of a blade, ...
s,
leaf blower A leaf blower, commonly known as a blower, is a device that propels air out of a nozzle to move debris such as leaves and grass cuttings. Leaf blowers are powered by electric or gasoline motors. Gasoline models have traditionally been two-strok ...
s, and
lawn mower A lawn mower (also known as a mower, grass cutter or lawnmower) is a device utilizing one or more revolving blades (or a reel) to cut a grass surface to an even height. The height of the cut grass may be fixed by the design of the mower, but g ...
s. This was made possible by low cost, high speed, and small footprint microcontrollers. Digital electronic ignition modules can be designed as either
capacitor discharge ignition Capacitor discharge ignition (CDI) or thyristor ignition is a type of automotive electronic ignition system which is widely used in outboard motors, motorcycles, lawn mowers, chainsaws, small engines, turbine-powered aircraft, and some cars. It w ...
(CDI) or
inductive discharge ignition Inductive discharge ignition systems were developed in the 19th century as a means to ignite the air–fuel mixture in the combustion chamber of internal combustion engines. The first versions were low tension coils, then low-tension and in turn ...
(IDI) systems. Capacitive discharge digital ignitions store charged energy for the spark in a capacitor within the module that can be released to the spark plug at virtually any time throughout the engine cycle via a control signal from the microprocessor. This allows for greater timing flexibility, and engine performance; especially when designed hand-in-hand with the engine
carburetor A carburetor (also spelled carburettor) is a device used by an internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the venturi tube in the main meteri ...
.


Engine management

In an
Engine Management System An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...
(EMS), electronics control fuel delivery and ignition timing. Primary sensors on the system are crankshaft angle (crankshaft or TDC position), airflow into the engine and
throttle A throttle is the mechanism by which fluid flow is managed by constriction or obstruction. An engine's power can be increased or decreased by the restriction of inlet gases (by the use of a throttle), but usually decreased. The term ''throttle'' ...
position. The circuitry determines which cylinder needs fuel and how much, opens the requisite injector to deliver it, then causes a spark at the right moment to burn it. Early EMS systems used an
analogue computer An analog computer or analogue computer is a type of computer that uses the continuous variation aspect of physical phenomena such as electrical, mechanical, or hydraulic quantities (''analog signals'') to model the problem being solved. In ...
to accomplish this, but as
embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded'' as ...
s dropped in price and became fast enough to keep up with the changing inputs at high revolutions,
digital Digital usually refers to something using discrete digits, often binary digits. Technology and computing Hardware *Digital electronics, electronic circuits which operate using digital signals **Digital camera, which captures and stores digital i ...
systems started to appear. Some designs using an EMS retain the original ignition coil, distributor and high-tension leads found on cars throughout history. Other systems dispense with the distributor altogether and have individual coils mounted directly atop each spark plug. This removes the need for both distributor and high-tension leads, which reduces maintenance and increases long-term reliability. Modern EMSs read in data from various sensors about the crankshaft position, intake manifold temperature, intake manifold pressure (or intake air volume), throttle position, fuel mixture via the oxygen sensor, detonation via a knock sensor, and exhaust gas temperature sensors. The EMS then uses the collected data to precisely determine how much fuel to deliver and when and how far to advance the ignition timing. With electronic ignition systems, individual cylinders can have their own individual timing so that timing can be as aggressive as possible per cylinder without fuel detonation. As a result, sophisticated electronic ignition systems can be both more fuel efficient, and produce better performance over their counterparts.


Turbine, jet and rocket engines

Gas turbine A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directi ...
engines, including
jet engine A jet engine is a type of reaction engine discharging a fast-moving jet of heated gas (usually air) that generates thrust by jet propulsion. While this broad definition can include rocket, Pump-jet, water jet, and hybrid propulsion, the term ...
s, have a CDI system using one or more igniter plugs, which are only used at startup or in case the
combustor A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the ''combustor'' or combustion chamber is fed ...
(s) flame goes out. Rocket engine ignition systems are especially critical. If prompt ignition does not occur, the
combustion chamber A combustion chamber is part of an internal combustion engine in which the fuel/air mix is burned. For steam engines, the term has also been used for an extension of the firebox which is used to allow a more complete combustion process. Interna ...
can fill with excess fuel and
oxidiser An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxi ...
and significant overpressure can occur (a "
hard start A hard start is a rocketry term referring to an overpressure condition during start of a rocket engine at ignition. In the worst cases, this takes the form of an unconfined explosion, resulting in damage, or destruction of the engine. Rocket igni ...
") or even an
explosion An explosion is a rapid expansion in volume associated with an extreme outward release of energy, usually with the generation of high temperatures and release of high-pressure gases. Supersonic explosions created by high explosives are known ...
. Rockets often employ
pyrotechnic device Pyrotechnics is the science and craft of creating such things as fireworks, safety matches, oxygen candles, explosive bolts and other fasteners, parts of automotive airbags, as well as gas-pressure blasting in mining, quarrying, and demolition. ...
s that place flames across the face of the
injector An injector is a system of ducting and nozzles used to direct the flow of a high-pressure fluid in such a way that a lower pressure fluid is entrained in the jet and carried through a duct to a region of higher pressure. It is a fluid-dynamic ...
plate, or, alternatively,
hypergolic A hypergolic propellant is a rocket propellant combination used in a rocket engine, whose components spontaneously ignite when they come into contact with each other. The two propellant components usually consist of a fuel and an oxidizer. The ...
propellants that ignite spontaneously on contact with each other. The latter types of engines do away with ignition systems entirely and cannot experience hard starts, but the propellants are highly toxic and corrosive. SpaceX's Raptor engine used for Starship and Super Heavy and the RS-25 engine used as the Space Shuttle Main Engine (SSME) used spark-ignition system. The Raptor engine needed to use spark-ignition because astronauts can't make pyrotechnic ignition systems or refill hypergolic fuel supply on the Moon or Mars, because the Lunar and Martian resources are very different from the resources of Earth.


See also

*
Electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...
*
Faraday's law of induction Faraday's law of induction (briefly, Faraday's law) is a basic law of electromagnetism predicting how a magnetic field will interact with an electric circuit to produce an electromotive force (emf)—a phenomenon known as electromagnetic inducti ...
*
Saab Direct Ignition Saab Direct Ignition is a capacitor discharge ignition developed by Saab Automobile, then known as Saab-Scania, and '' Mecel AB'' during the 1980s. It was first shown in 1985 and put into series production in the Saab 9000 in 1988. One of the fi ...
*
Spark-ignition A spark-ignition engine (SI engine) is an internal combustion engine, generally a petrol engine, where the combustion process of the air-fuel mixture is ignited by a spark from a spark plug. This is in contrast to compression-ignition engines, t ...


References


External links


Ignition apparatus for explosion-motors.
Charles F. Kettering 15 September 1909/3 September 1912 "Ignition Apparatus for Explosion-Motors" no capacitor, no points, separate coils
Ignition system.
Charles F. Kettering 2 November 1910/3 September 1912 "Ignition System" distributor with capacitor 46 (not points)
Ignition system.
Charles F. Kettering 11 August 1911/17 April 1917 "Ignition System" points, no capacitor, ignition switch to avoid draining the battery
Ignition system
John A. Hawthorne 1964/1967 comments about Kettering ignition system: "Practical efforts to improve or supplant this system have failed, and it has remained virtually unchanged through the years. However, the present trend toward higher performance automobile engines threatens to render this tried and true system obsolete. The principal limitation of the Kettering system is, as typically applied, the inability to develop adequate levels of spark plug gap energy without sacrificing longevity of the ignition points or the transformer coil. The inherent inefficiency of the system is particularly apparent at higher engine speeds." {{DEFAULTSORT:Ignition System Auto parts Applications of control engineering Engine components