Ignition system

Coil-on-plug ignition module

Distributor cap

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 engines, oil-fired and gas-fired boilers, rocket engines, 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 glowplugs that preheat the combustion chamber to aid 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 ignition was probably Alessandro Volta's toy electric pistol from the 1780s.

Siegfried Marcus patented his "Electrical igniting device for gas engines" on 7 October 1884. ^[1]

Magneto and mechanical systems

Ignition magneto systems

Ignition magneto

Main article: Ignition magneto

An ignition magneto (also called a high-tension magneto) is an older type of ignition system used in spark-ignition engines (such as petrol engines). It uses a magneto and a transformer to make pulses of high voltage for the spark plugs. The older term "high-tension" means "high-voltage".

Used on many cars in the early 20th century, ignition magnetos were largely replaced by induction coil ignition systems. The use of ignition magnetos is now confined mainly to engines without a battery, for example in lawnmowers and chainsaws. It is also used in modern piston-engined aircraft^{[ citation needed ]} (even though a battery is present), to avoid the engine relying on an electrical system.

Induction coil systems

Main article: Trembler coil

As batteries became more common in cars (due to the increased usage of electric starter motors), magneto systems were replaced by systems using an induction coil. The 1886 Benz Patent-Motorwagen and the 1908 Ford Model T used a trembler coil ignition system, whereby the trembler interrupted the current through the coil and caused a rapid 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. ^[2]

Distributor-based systems

Rotor contacts inside distributor cap

Main article: Distributor

An improved ignition system was invented by Charles Kettering at Delco in the United States and introduced in Cadillac's 1912 cars. ^[3] The Kettering ignition system consisted of a single ignition coil, breaker points, a capacitor (to prevent the points from arcing at break) and a distributor (to direct the electricity from the ignition coil to the correct cylinder). The Kettering system became the primary ignition system for many years in the automotive industry due to its lower cost and relative simplicity.^{[ citation needed ]}

Electronic systems

See also: Capacitor discharge ignition

The first electronic ignition (a cold cathode type) was tested in 1948 by Delco-Remy, ^[4] while Lucas introduced a transistorized ignition in 1955, which was used on BRM and Coventry Climax Formula One engines in 1962. ^[4] The aftermarket began offering EI that year, with both the AutoLite Electric Transistor 201 and Tung-Sol EI-4 (thyratron capacitive discharge) being available. ^[5] Pontiac 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 Corvettes. ^[5] The first commercially available all solid-state (SCR) capacitive discharge ignition was manufactured by Hyland Electronics in Canada also in 1963. Ford fitted a FORD designed breakerless system on the Lotus 25s entered at Indianapolis 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 hemis in 1963 and 1964. ^[5]

Prest-O-Lite's CD-65, which relied on capacitance discharge (CD), appeared in 1965, and had "an unprecedented 50,000 mile warranty." ^[5] (This differs from the non-CD Prest-O-Lite system introduced on AMC products in 1972, and made standard equipment for the 1975 model year.) ^[5] A similar CD unit was available from Delco in 1966, ^[4] which was optional on Oldsmobile, Pontiac, and GMC vehicles in the 1967 model year. ^[5] Also in 1967, Motorola debuted their breakerless CD system. ^[5] 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 was the first production car to come standard with EI in 1968, followed by the Jaguar XJ Series 1 ^[6] in 1971, Chrysler (after a 1971 trial) in 1973 and by Ford and GM in 1975. ^[5]

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 and Plymouth on their factory Super Stock Coronet and Belvedere drag racers. ^[5] This amplifier was installed on the interior side of the cars' firewall, and had a duct which provided outside air to cool the unit.^{[ citation needed ]} 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.

A variation coil-on-plug ignition has each coil handle two plugs, on cylinders which are 360 degrees out of phase (and therefore reach top dead center (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" 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. ^[7] 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.

Engine management

In an Engine Management System (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 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 to accomplish this, but as embedded systems dropped in price and became fast enough to keep up with the changing inputs at high revolutions, digital 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^{[ citation needed ]} 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 engines, including jet engines, have a CDI system using one or more igniter plugs, which are only used at startup or in case the combustor(s) flame goes out.

Rocket engine ignition systems are especially critical. If prompt ignition does not occur, the combustion chamber can fill with excess fuel and oxidiser and significant overpressure can occur (a "hard start") or even an explosion. Rockets often employ pyrotechnic devices that place flames across the face of the injector plate, or, alternatively, hypergolic 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 not 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
• Faraday's law of induction
• History of the internal combustion engine
• Saab Direct Ignition
• Spark-ignition

References

1. Specifications and Drawings of Patents Relating to Electricity Issued by the U. S., Volume 37, Published 1886
2. Patterson, Ron; Coniff, Steve (November–December 2003). "The Model T Ford Ignition System & Spark Timing" (PDF). Model T Times.
3. "Charles F. Kettering, inventor of electric self-starter, is born". HISTORY.
4. Super Street Cars, 9/81, p.34.
5. Super Street Cars, 9/81, p.35.
6. "The new Jaguar V12 - Motor Sport Magazine Archive". Motor Sport Magazine. 7 July 2014.
7. northstarperformance.com, fixya.com, i.fixya.net

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."