Engine Control Unit (ECU)

An Engine control unit (ECU) is an Electronic control unit, controls various aspects of an internal combustion engines’ operation.

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 monitoring and control is done using a control loop (such as a PID controller).

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 other peripherals.

ECU Capable For Audi

ECU Capable For Audi

Hybrid digital designs:

A hybrid digital design was popular in the mid 1980s. These used analogue techniques to measure and process input parameters from the engine, and then used a look-up table stored in a digital ROM chip to yield pre-computed output values. Later systems compute these outputs dynamically. The ROM type of system is amenable to tuning if one knows the system well.

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), ceramic substrate or a thin laminate substrate. 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 or replacing chips. This is also referred to as an (electronic) Engine Management System (EMS).

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 waste gates 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.

Modern ECUs sometimes include features as cruise control, transmission control, anti-skid brake control, and anti-theft control, etc.