An engine control unit (ECU) controls the air-fuel ratio. It determines the amount of fuel that needs to be injected. The throttle position sensor indicates the throttle position. The mass flow sensor tells the excess amount of air being sucked. Based on these parameters, the ECU injects the desired amount of fuel into the engine. Fuel will also be injected if the engine control temperature sensor shows that the engine needs more warming.
An ECU also controls the ignition timing to provide improved economy and power. On noticing a knock, it adjusts the timing of the spark appropriately. If the knock is due to low revolution per minute (RPM) then ECU manages automatic transmission and changes to a lower gear.
Some ECUs have idle speed control. The crankshaft position sensor monitors the revolution speed of the engine which has a primary role in functions such as spark events, fuel injection, and valve timing. A programmable throttle controls the idle speed scarico sportivo Maserati MC20.
In engines with variable valve timing, the ECU controls the time of valve opening thus optimizing the airflow into the cylinder. It helps the electronic valve control system in selecting a set of lobes in the camshaft. These sets of lobes are designed for low and high RPM.
New technologies have brought forth engines that do not have camshafts. Opening and closing of the intake and exhaust valves are fully controlled electronically. These engines do not need a starter motor. Torque and horsepower are significantly improved. Such engines are more energy efficient and less polluting. Matching ECU is in place for such engines.
Programmable ECUs have also been introduced in the market for those engines that have been substantially modified, reworked, and reconditioned. There are upgraded engines in which the intercourse or turbocharger has been changed or added, the exhaust system has been changed or the engine has been converted to run on an alternative fuel. In the aforementioned situation, a programmable ECU can be plugged in. ECU is programmed by mapping on a worksheet in a connected laptop. It maps the amount of fuel to be injected into the cylinder, ignition timing, revolution limits, water temperature correction, transient fueling, a low fuel pressure modifier, and closed loop lambda. Advanced stand-alone ECU also includes functions like waste gate control, stage injection, gear control, variable cam timing, etc. An ECU used in race cars may have special software for recording data related to all sensors for subsequent analysis and desired corrections.
The latest innovation in ECU incorporates microprocessors which enable the processing of engine inputs in real-time.