An engine control unit (ECU) is an electronic control unit which controls various aspects of an internal combustion engine's operation. The simplest ECUs control only the quantity of fuel injected into each cylinder each engine cycle. More advanced ECUs found on most modern cars also control the ignition timing, variable valve timing (VVT), the level of boost maintained by the turbocharger (in turbocharged cars), and control other peripherals. In automotive electronics, an electronic control unit (ECU) is an embedded microcomputer that controls one or more of the electrical subsystems in a vehicle. ... A colorized automobile engine The internal combustion engine is an engine in which the combustion of fuel and an oxidizer (typically air) occurs in a confined space called a combustion chamber. ... Ignition timing in an internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity. ... Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. ... Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ...

E11: An aftermarket ECU

ECUs determine the quantity of fuel, ignition timing and other parameters by monitoring the engine through sensors. These can include, MAP sensor, throttle position sensor, air temperature sensor, oxygen sensor and many others. Often this is done using a control loop (such as a PID controller). Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A MAP Sensor (manifold absolute pressure) is a sensor used as part of an internal combustion engines electronic control system. ... Throttle body showing throttle position sensor on the right A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. ... // An oxygen sensor is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analyzed. ... A control system is a device or set of devices to manage, command, direct or regulate the behaviour of other devices or systems. ... A proportional-integral-derivative controller (PID controller) is a generic control loop feedback mechanism widely used in industrial control systems. ...

Before ECUs most engine parameters were fixed. The quantity of fuel per cylinder per engine cycle was determined by a carburetor or injector pump. Bendix-Technico (Stromberg) 1-barrel downdraft carburetor model BXUV-3, with nomenclature A carburetor (North American spelling) / carburettor (international spelling), colloquially called a carb (in North America and the United Kingdom) or carby (chiefly in Australia), is a device that blends air and fuel for an internal combustion engine. ...

ECU operation

Control of fuel injection

For an engine with fuel injection, an ECU will determine the quantity of fuel to inject based on a number of parameters. If the throttle pedal is pressed further down, this will open the throttle body and allow more air to be pulled into the engine. The ECU will inject more fuel according to how much air is passing into the engine. If the engine has not warmed up yet, more fuel will be injected (causing the engine to run slightly 'rich' until the engine warms up). // Multi Port Fuel injection is a means of metering fuel into an internal combustion engine. ...

Control of ignition timing

A spark ignition engine requires a spark to initiate combustion in the combustion chamber. An ECU can adjust the exact timing of the spark (called ignition timing) to provide better power and economy. If the ECU detects knock, a condition which is potentially destructive to engines, and "judges" it to be the result of the ignition timing being too early in the compression stroke, it will delay (retard) the timing of the spark to prevent this. The term spark-ignition is normally used to refer to internal combustion engines where the fuel-air mixture is ignited with a spark. ... Ignition timing in an internal combustion engine is the process of setting the time that a spark will occur in the combustion chamber (during the power stroke) relative to piston position and crankshaft angular velocity. ... Knocking (also called pinking or pinging)— colloquially detonation—in internal combustion engines occurs when air/fuel mixture in the cylinder detonates or ignites prior to the timed pre-set conditions in the engines cylinder(s). ...

A second, more common source, cause, of knock/ping is operating the engine in too low of an RPM range for the "work" requirement of the moment. In this case the knock/ping results from the piston not being able to move downward as fast as the flame front is expanding.

But this latter mostly applies only to manual transmission equipped vehicles. The ECU controlling an automatic transmission would simply downshift the transmission were this the cause of knock/ping.

Control of variable valve timing

Some engines have Variable Valve Timing. In such an engine, the ECU controls the time in the engine cycle at which the valves open. The valves are usually opened later at higher speed than at lower speed. This can optimise the flow of air into the cylinder, increasing power and economy. Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. ...

Control of starting

A relatively recent application of engine control is the use of precisely timed injection and ignition to start an engine without the use of a starter motor. Such a static-start engine would provide the efficiency and pollution-reductiton improvements of a mild hybrid-electric drive, but without the expense and complexity of an oversized starter motor.^[1] Petroleum electric hybrid vehicles make use of both an on-board rechargeable energy storage system (RESS) and a fueled power source for vehicle propulsion. ...

Programmable ECUs

A special category of ECUs are those which are programmable. These units do not have a fixed behavior, but can be reprogrammed by the user.

Programmable ECUs are required where significant aftermarket modifications have been made to a vehicle's engine. Examples include adding or changing of a turbocharger, adding or changing of an intercooler, changing of the exhaust system, and conversion to run on alternative fuel. As a consequence of these changes, the old ECU may not provide appropriate control for the new configuration. In these situations, a programmable ECU can be wired in. These can be programmed/mapped with a laptop connected using a serial or USB cable, while the engine is running. Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ... An intercooler, or charge air cooler, is an air-to-air or air-to-liquid heat exchange device used on turbocharged and supercharged internal combustion engines to improve their volumetric efficiency by increasing intake air charge density through isochoric cooling. ... Look up exhaust in Wiktionary, the free dictionary. ... The definition of alternative fuel varies according to the context of its usage. ... For the band, see Laptop (band). ... Note: USB may also mean upper sideband in radio. ...

The programmable ECU may control the amount of fuel to be injected into each cylinder. This varies depending on the engine's RPM and the position of the gas pedal (or the manifold air pressure). The engine tuner can adjust this by bringing up a spreadsheet-like page on the laptop where each cell represents an intersection between a specific RPM value and a gas pedal position (or the throttle position, as it is called). In this cell a number corresponding to the amount of fuel to be injected is entered. // Multi Port Fuel injection is a means of metering fuel into an internal combustion engine. ... A MAP Sensor (manifold absolute pressure) is a sensor used as part of an internal combustion engines electronic control system. ... Screenshot of a spreadsheet under OpenOffice A spreadsheet is a rectangular table (or grid) of information, often financial information. ... Throttle body showing throttle position sensor on the right A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. ...

By modifying these values while monitoring the exhausts using a wide band lambda probe to see if the engine runs rich or lean, the tuner can find the optimal amount of fuel to inject to the engine at every different combination of RPM and throttle position. This process is often carried out at a dynamometer, giving the tuner a controlled environment to work in. An automotive lambda probe, also known as a lambda sensor, O2 sensor, oxygen sensor, lambda sond or EGO (exhaust gas oxygen) sensor, is a small sensor inserted into the exhaust system of a petrol engine to measure the volume of oxygen (O2) remaining in the exhaust gas to allow an... A dynamometer, or dyno for short, is a machine used to measure torque and rotational speed (rpm) from which power produced by an engine, motor or other rotating prime mover can be calculated. ...

Other parameters that are often mappable are:

• Ignition: Defines when the spark plug should fire for a cylinder.
• Rev limit: Defines the maximum RPM that the engine is allowed to rev to. After this fuel and/or ignition is cut.
• Water temperature correction: Allows for additional fuel to be added when the engine is cold (choke).
• Transient fueling: Tells the ECU to add a specific amount of fuel when throttle is applied.
• Low fuel pressure modifier: Tells the ECU to increase the injector fire time to compensate for a loss of fuel pressure.
• Closed loop lambda: Lets the ECU monitor a permanently installed lambda probe and modify the fueling to achieve stoichiometric (ideal) combustion.

Some of the more advanced race ECUs include functionality such as launch control, limiting the power of the engine in first gear to avoid burnouts. Other examples of advanced functions are: This article or section should include material from Spark gap A spark plug is an electrical device that fits into the cylinder head of some internal combustion engines and ignites compressed aerosol gasoline by means of an electric spark. ... For other uses, see Revolutions per minute (disambiguation). ... In an engine, the throttle is the mechanism by which the engines power is increased or decreased. ... // An oxygen sensor is an electronic device that measures the proportion of oxygen (O2) in the gas or liquid being analyzed. ... In chemistry, stoichiometry is the study of the combination of elements in chemical reactions. ... Launch control refers to an electronic device that is used to assist a Formula 1 driver in the very moment of the start of a race. ...

• Waste gate control: Sets up the behavior of a turbo waste gate, controlling boost.
• Banked injection: Sets up the behavior of double injectors per cylinder, used to get a finer fuel injection control and atomization over a wide RPM range.
• Variable cam timing: Tells the ECU how to control variable intake and exhaust cams.
• Gear control: Tells the ECU to cut ignition during (sequential gearbox) upshifts or blip the throttle during downshifts.

A race ECU is often equipped with a data logger recording all sensors for later analysis using special software in a PC. This can be useful to track down engine stalls, misfires or other undesired behaviors during a race by downloading the log data and looking for anomalies after the event. The data logger usually has a capacity between 0.5 and 16 Mbytes. A wastegate is a valve that diverts exhaust gases away from the turbine wheel in a turbocharged engine system. ... Look up boost in Wiktionary, the free dictionary. ... Variable Cam Timing (VCT) is an automobile variable valve timing technology developed by Ford. ... Semi-automatic transmission, or also known as clutchless manual transmission, automated manual transmission, e-gear, or paddle shift gearbox is a system which uses electronic sensors, processors and actuators to do gear shifts on the command of the driver. ...

In order to communicate with the driver, a race ECU can often be connected to a "data stack", which is a simple dash board presenting the driver with the current RPM, speed and other basic engine data. These race stacks, which are almost always digital, talk to the ECU using one of several proprietary protocols running over RS232, CANbus]].

ECU flashing

Example reflash tuning software

Many recent (around 1996 or newer) cars use OBD-II ECUs that are sometimes capable of having their programming changed through the OBD port. Automotive enthusiasts with modern cars take advantage of this technology when tuning their engines. Rather than use an entire new engine management system, one can use the appropriate software to adjust the factory equipped computer. By doing so, it is possible to retain all stock functions and wiring while using a custom tuned program. This should not be confused with "chip tuning", where the owner has ECU ROM physically replaced with a different one -- no hardware modification is (usually) involved with flashing ECUs, although special equipment is required. Image File history File links Download high-resolution version (1216x902, 140 KB)[edit] Summary [Ecuedit] editor with a USDM 2004 Subaru WRX STI ROM opened. ... Image File history File links Download high-resolution version (1216x902, 140 KB)[edit] Summary [Ecuedit] editor with a USDM 2004 Subaru WRX STI ROM opened. ... OBD-II (OnBoard Diagnostics version 2) is a common hardware diagnostics interface that is present on all cars sold in the United States after 1996. ...

Factory engine management systems often have similar controls as aftermarket units intended for racing, such as 3-dimensional timing and fuel control maps. They generally do not have the ability to control extra ancillary devices, such as variable valve timing if the factory vehicle was a fixed geometry camshaft or boost control if the factory car was not turbocharged. Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. ... Boost control is the principle of controlling the boost level produced in the intake manifold of a turbocharged or supercharged engine by affecting the air pressure delivered to the pneumatic and mechanical wastegate actuator. ...

History

Hybrid digital designs

A hybrid digital design was popular in the mid-'80s. This used analogue techniques to measure and process input parameters from the engine, then used a look-up 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 is less able to compensate than a CPU based system. In computer science, a lookup table is a data structure, usually an array or associative array, used to replace a runtime computation with a simpler lookup operation. ... Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. ... Engine tuning or engine building is the adjustment, modification or design of internal combustion engines to yield optimal performance, either in terms of power output or economy. ...

Sophisticated engine management systems receive inputs from other sources, and control other parts of the engine; for instance, some variable valve timing systems are electronically controlled, and turbocharger wastegates can also be managed. They also may communicate with transmission control units or directly interface electronically-controlled automatic transmissions, traction control systems, and the like. The Controller Area Network or CAN bus automotive network is often used to achieve communication between these devices. Variable valve timing, or VVT, is a generic term for an automobile piston engine technology. ... Air foil bearing-supported turbocharger cutaway made by Mohawk Innovative Technology Inc. ... A Transmission Control Unit is a device that controls modern electronic automatic transmissions. ... The automatic gear selector in a Ford Five Hundred vehicle An automatic transmission (commonly abbreviated as AT) is an automobile gearbox that can change gear ratios automatically as the vehicle moves, thus freeing the driver from having to shift gears manually (similar but larger devices are also used for railroad... Traction control systems, on current production vehicles, are typically (but not necessarily) electro-hydraulic systems designed to prevent loss of traction (and therefore the control of the vehicle) when excessive throttle or steering is applied by the driver. ... Controller Area Network (CAN) is a broadcast, differential serial bus standard, originally developed in the 1980s by Robert Bosch GmbH, for connecting electronic control units (ECUs). ...

Modern ECUs

Modern ECUs use a microprocessor which can process the inputs from the engine sensors in real time. An electronic control unit contains the hardware and software (firmware). The hardware consists of electronic components on a printed circuit board (PCB). The main component on this circuit board is a microcontroller chip (CPU). The software is stored in the microcontroller or other chips on the PCB, typically in EPROMs or flash memory so the CPU can be re-programmed by uploading updated code. This is also referred to as an (electronic) Engine Management System (EMS). A microprocessor is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). ... It has been suggested that Real-time computing be merged into this article or section. ... A microcontroller, like this PIC18F8720 is controlled by firmware stored inside on FLASH memory In computing, firmware is a computer program that is embedded in a hardware device, for example a microcontroller. ... Part of a 1983 Sinclair ZX Spectrum computer board. ... CPU can stand for: in computing: Central processing unit in journalism: Commonwealth Press Union in law enforcement: Crime prevention unit in software: Critical patch update, a type of software patch distributed by Oracle Corporation in Macleans College is often known as Ash Lim. ... EPROM. The small quartz window admits UV light during erasure. ... A USB flash drive. ...

Other applications

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 aeroplanes than in automobiles, because of the large costs of certifying parts for aviation use, relatively small demand, and the consequent stagnation of technological innovation in this market. Also, a carburated engine with magneto ignition and a gravity feed fuel system does not require any electrical power to run, which is a safety bonus. FADEC is the acronym for Full Authority Digital Engine Control. ... Airplane and Aeroplane redirect here. ... Bendix-Technico (Stromberg) 1-barrel downdraft carburetor model BXUV-3, with nomenclature A carburetor (North American spelling) / carburettor (international spelling), colloquially called a carb (in North America and the United Kingdom) or carby (chiefly in Australia), is a device that blends air and fuel for an internal combustion engine. ... A magneto provides pulses of electrical power to the spark plugs in some gasoline-powered internal combustion engines where batteries are not available, most commonly those in 2-stroke and 4-stroke engines used in small motorcycles, lawnmowers and chainsaws. ...

ECU failures

As usually occurs with a technology shift, computer-controlled engine management has replaced old failure modes with new ones^{[citation needed]}. With advanced age, a failing ECU can cause seemingly random starting and driveability faults. For example, a vehicle may refuse to start when cranked with the starter motor, but may respond easily to a push start. Failing electrolytic capacitors in the ECU no longer smooth the power supply to the microprocessor, and the varying load on the starter motor causes sufficient line voltage fluctuation that the computer reboots repeatedly while attempting to start the engine^{[citation needed]}. An industry has evolved to refurbish ECUs with this and other types of failures related to age and use. In 1903, the first U.S. patent for an automobile electric self-starter was issued to Clyde J. Coleman of New York City (No. ... Electrolytic capacitors An electrolytic capacitor is a type of capacitor typically with a larger capacitance per unit volume than other types, making them valuable in relatively high-current and low-frequency electrical circuits. ...

See also

• Air flow meter
• Malfunction Indicator Lamp
• Trionic 8
• Fuel injection
• Automobile self starter

An air flow meter, also know as air consumption meter, is a device that measures how much air is flowing through a tube. ... A Malfunction Indicator Lamp, this one labeled Service Engine Soon. A Malfunction Indicator Lamp (MIL) is an indicator of the internal status of a car engine. ... This does not cite its references or sources. ... // Multi Port Fuel injection is a means of metering fuel into an internal combustion engine. ... An automobile self-starter is an electric motor that initiates piston motion in a cars internal combustion engine before it can power itself. ...

Manufacturers of Aftermarket ECUs

• Adaptronic
• AEM
• Apex'i
• ATP Electronics
• Autronic
• Bowling & Grippo (Makers of MegaSquirt open source ECU)
• Electromotive TEC³r and TECgt
• EMS Aftermarket Engine Management
• FAAR Industry
• Haltech Engine Management Systems
• Hondata
• Link ElectroSystems
• Microtech
• Motec
• Performance Electronics, Ltd.
• Perfect Power
• Simple Digital Systems

AEM is a three-letter abbreviation with multiple meanings, as described below: AEM (1924 automobile), a French elctric car; AEM (1987 automobile), a Welsh-built version of the Mini-Moke car; AEM (label), a record label This page concerning a three-letter acronym or abbreviation is a disambiguation page—a... MegaSquirt is an aftermarket electronic fuel injection (EFI) controller designed to be used with a wide range of internal combustion engines. ... Link ElectroSystems Ltd. ... MoTeC makes engine control units as well as instrumentation and data logging equipment, including telemetry. ...

Open source engine management systems

• CarDAQ-plus J2534 pass-thru hardware device

DIY engine management systems

• VEMS group

External links

This article or section includes a list of references or external links, but its sources remain unclear because it lacks in-text citations. You can improve this article by introducing more precise citations.

• Articles from Toyota Motor Sales, USA, Inc. at Autoshop 101
• Explanation of the SAE J2534-1 Standard for pass-thru programming of ECUs
• LabVIEW VIs for developing test systems with vehicle PassThru (J2534-1)
• Forum discussion of J2534 devices and software at Tuner Tools,llc
• Interesting tool used by ECU developers to electrically emulate four-stroke engine signals