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Engine control unit

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For other uses, see ECU (disambiguation).
An ECU from a 1996 Chevrolet Beretta

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 reading values from a multitude of sensors within the engine bay, interpreting the data using multidimensional performance maps (called lookup tables), and adjusting the engine actuators. Before ECUs, air–fuel mixture, ignition timing, and idle speed were mechanically set and dynamically controlled by mechanical and pneumatic means.

If the ECU has control over the fuel lines, then it is referred to as an electronic engine management system (EEMS). The fuel injection system has the major role of controlling the engine's fuel supply. The whole mechanism of the EEMS is controlled by a stack of sensors and actuators.

Functions

The main functions of the ECU are typically:

The sensors used by the ECU include:

Secondary

Other functions include:

In a camless piston engine (an experimental design not currently used in any production vehicles), the ECU has continuous control of when each of the intake and exhaust valves are opened and by how much.[1]

Early systems

One of the earliest attempts to use such a unitized and automated device to manage multiple engine control functions simultaneously was the created by BMW in 1939 Kommandogerät system used by the BMW 801 14-cylinder radial engine which powered the Focke-Wulf Fw 190 V5 fighter aircraft.[2] This device replaced the 6 controls used to initiate hard acceleration with one control, however the system could cause surging and stalling problems.[citation needed]

Usage in motor vehicles

The development of integrated circuits and microprocessors made engine control economically feasible in the 1970s. In the early 1970s, the Japanese electronics industry began producing integrated circuits and microcontrollers for engine control in Japanese automobiles.[3] The Ford EEC (Electronic Engine Control) system, which utilized the Toshiba TLCS-12 microprocessor, went into mass production in 1975.[4]

Hybrid digital or analog designs were popular in the mid-1980s. This used analog techniques to measure and process input parameters from the engine, then used a lookup table stored in a digital ROM chip to yield precomputed output values. Later systems compute these outputs dynamically. The ROM type of system is amenable to tuning if one knows the system well. The disadvantage of such systems is that the precomputed values are only optimal for an idealised, new engine. As the engine wears, the system may be less able to compensate compared to other designs.

General Motors' (GM) first ECUs had a small application of hybrid digital ECUs as a pilot program in 1979, but by 1980, all active programs were using microprocessor based systems. Due to the large ramp up of volume of ECUs that were produced to meet the Clean Air Act requirements for 1981, only one ECU model could be built for the 1981 model year.[5] In 1988 Delco (GM's electronics division), had produced more than 28,000 ECUs per day, making it the world's largest producer of on-board digital control computers at the time.[6]

Usage in aircraft engines

Such systems are used for many internal combustion engines in other applications. In aeronautical applications, the systems are known as "FADECs" (Full Authority Digital Engine Controls). This kind of electronic control is less common in piston-engined light fixed-wing aircraft and helicopters than in automobiles. This is due to the common configuration of a carbureted engine with a magneto ignition system that does not require electrical power generated by an alternator to run, which is considered a safety advantage.[7]

See also

References

  1. ^ Austen, Ian (2003-08-21). "WHAT'S NEXT; A Chip-Based Challenge to a Car's Spinning Camshaft". The New York Times. Retrieved 2009-01-16.
  2. ^ Gunston, Bill (1989). World Encyclopedia of Aero Engines. Cambridge, England: Patrick Stephens Limited. p. 26. ISBN 978-1-85260-163-8.
  3. ^ "Trends in the Semiconductor Industry: 1970s". Semiconductor History Museum of Japan. Retrieved 27 June 2019.
  4. ^ "1973: 12-bit engine-control microprocessor (Toshiba)" (PDF). Semiconductor History Museum of Japan. Retrieved 27 June 2019.
  5. ^ GM Emission Control Project Center – I Was There – GMnext
  6. ^ Delco Electronics Electron Magazine, The Atwood Legacy, Spring '89, page 25
  7. ^ Pilot's Encyclopedia of Aeronautical Knowledge. Federal Aviation Administration.
  8. ^ "SECU3 open source ECU".SECU-3
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