Engine Management ECU (EMS ECU)

From Wikipedia,

“ 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. “

Engine control units accomplishes various functions but the most important aim is to calculate amount of fuel and​ exact moment of injection​ based on driver demand from the accelerator pedal ,other engine loads and temperature etc… and thereby providing better fuel efficiency , performance and meeting legal emission requirements. Crank ,camshaft sensors ,pedal position sensors are the primary sensors and injection and ignition valves are the main actuators

If we go into detailed working of EMS,there are 5 major subsystems

• Injection /ignition System — injectors,ignition coil,speed sensors,etc..
• Air Intake system — main components include throttle position sensor,turbocharger/supercharger,etc..
• Exhaust system — main components include lamda sensor,Lean NOx trap,Selective catalytic reduction etc…
• Fuel system — Fuel pump,Fuel tank , fuel pressure sensor,etc..
• Miscellaneous sensors and loads — Alternator,AC,Heater.etc..

Injection/Ignition System

For gasoline systems the ignition system generates sparks that are necessary for igniting the air-fuel mixture. The optimal ignition timing is calculated by the engine ECU according to each driving condition and it makes the ignition coil to generates high voltage which is then applied to the spark plug electrodes to generate spark ignition.

Air Intake System

The optimal air/fuel ratio for complete com-bustion is 14.5 parts air to 1 part fuel by volume.(for a Gasoline System, for Diesel system it is 14.7:1). This is referred to as the stoichiometric ratio. Mixture corrections must be made as required to satisfy the differing engine demands encountered under any given driving condition. The intake system adjusts the air volume required for combustion which involves detection of intake air volume by a mass airflow sensor. Air is filtered by the air cleaner after this and the volume adjustment is performed by the throttle valve.ECU takes the input from mas airflow sensor and other sensors and controls the throttle

Air pressure can also be controlled by turbocharger by ECUs in Diesel vehicles

Different Exhaust elements are controlled differently.To control Nitrogen oxides different method are used which include exhaust gas recirculation,NOx storage catalyst and selective catalytic reduction.ECU controls these devices based on the different sensors(Nox sensor or other sensors) to reduce the emission, also injection/ignition and air inflow is also controlled accordingly.To decrease partculate matter particulate filter is used.To decrease hydrocarbons and arbon monoxide ,Diesel oxidation catalyst is used

Fuel system

The fuel system controls the fuel supply required for combustion. ECU controls the fuel pump and pumps the fuel and maintains pressure at constant required level, and the surplus fuel is returned to the fuel tank. The fuel then travels through the fuel filter where dust and moisture are removed, passes through the delivery pipe, and is fed to the injectors

Miscellaneous

ECU can also control Heater , AC and can support other features like OBDII etc..

Originally published at https://www.vtronics.in on September 9, 2019.