Engine management SystemNowadays every engine today is controlled by computer. Any engine certified for on-highway use since 1998 has been computer controlled. Onboard vehicle computers are referred to as engine/electronic control modules (ECM) or engine/electronic control units (ECU).

What is Engine Management? It is the management of ignition, fuelling

and exhaust requirements of the engine to ensure smooth power delivery and optimum running.

Since 1980’s more focus is on electronic engine management due to enactment of increasingly stricter emission laws.

Electronic Engine Management Basic components are:1. Electronic Control Module2. Fuel Delivery System3. Ignition System4. Sensors

1.Electronic Control Module Definition:

An engine control module (ECM), most commonly called the powertrain control module (PCM), controls a series of actuators on an internal combustion engine to ensure the optimum running. It does this by reading values from a multitude of sensors within the engine bay, interpreting the data using multidimensional performance maps (called Look-up tables), and adjusting the engine actuators accordingly.

1.Electronic Control Module The ECM is the engine controller and controls

the parameters of an internal combustion engine.

The ECM contains a microprocessor, computer memory, and usually an output or switching apparatus.

The ECM senses how wide the throttle is opened. The ECM controls fuel delivery and spark timing

by receiving information from sensors. It process information hundreds of times per

second. It is programmed by the Manufacturer.

ECM Running Modes Open-loop : This is when the ECM is not using

input data from sensors. This occurs in certain circumstances where using input

data would not be beneficial. Such as: when the engine is cold, or wide open throttle.

Closed-loop: This uses post-combustion data to compute changes for pre-combustion parameters.

This change was implemented as the microprocessors got faster and EPA standards got tighter. Some use data from short period of time 1trip others keep track of data for months.

Some ECM Parameters Engine Load - Computed from Air Flow Rate into the engine and

Intake Manifold air pressure Engine Speed - Reported by the Crankshaft Position Sensor Coolant Temperature - Reported by the engine coolant sensor, a

thermistor that varies its resistance according to the engine coolant temperature

Throttle Position - Throttle position sensor creates a voltage signal that varies in proportion to the throttle valve opening angle

Intake Air Temperature - Measured by another thermistor located in the Mass Air Flow Sensor unit

Battery Voltage - Battery voltage affects the speed at which the fuel injectors open and must be taken into account in computing the fuel injector pulse length, or injector open time

Oxygen Sensor - The oxygen density in the exhaust emissions is

detected and generates a control signal back to the ECU indicating the burned air/fuel ratio.

2.Fuel Delivery System The fuel line passes through

a pressure regulator which feeds each injector.

The surplus fuel is headed back to the tank in the return line. The air is taken from the atmosphere. It is mixed with fuel just before the inlet valve by the fuel injector.

This fuel delivery system is controlled by ECU to provide lean and rich mixtures depending on operating conditions.

3.Ignition System To maximize the Engine

output, spark should be at the precise moment.

Maximum combustion chamber pressure can be attained.

A mechanical advance distributor is used for this.

A spark advance map is developed and stored in the ECU.

As the speed increases, the spark should be advanced further.

4. SensorsHere is a list of sensors which are monitored by the ECU:1. Pressure Sensor (How dense is the air going into the engine) -

Needed for fuel calculations2. Throttle Sensor (How open the throttle is to allow more/less

air in)3. Water Temperature (What temperature is the engine

operating at) - Colder engine equals colder intake air in turn more fuel is needed

4. Intake Air Sensor (How cold is the air going into the engine) - Needed for fuel calculations

5. Fuel Temperature Sensor ( Measures the temp of the fuel) - safety feature

6. Oxygen Sensor (Measures the amount of air left in the exhaust gas)- Needed for fuel adjustments

Working of ECU:

ECU

Control of Air/Fuel ratio: For an engine with fuel injection, an engine control

unit (ECU) will determine the quantity of fuel to inject based on a number of parameters. If the Throttle position sensor is showing the throttle pedal is pressed further down, the Mass flow sensor will measure the amount of additional air being sucked into the engine and the ECU will inject fixed quantity of fuel into the engine ( most of the engine fuel inlet quantity is fixed). If the Engine coolant temperature sensor is showing the engine has not warmed up yet, more fuel will be injected (causing the engine to run slightly 'rich' until the engine warms up).

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. Since knock tends to occur more easily at lower rpm, the ECU may send a signal for the automatic transmission to downshift as a first attempt to alleviate knock.

Control of Idle Speed: The engine RPM is monitored by the crankshaft position

sensor which plays a primary role in the engine timing functions for fuel injection, spark events, and valve timing. Idle speed is controlled by a programmable throttle stop or an idle air bypass control stepper motor. Effective idle speed control must anticipate the engine load at idle. Changes in this idle load may come from power steering systems, power brake systems, and electrical charging and supply systems. Engine temperature and transmission status, and lift and duration of camshaft also may change the engine load and/or the idle speed value desired.

A full authority throttle control system may be used to control idle speed, provide cruise control functions and top speed limitation.

Electronic valve control: Electronic valve control drastically improve torque and

horsepower, while reducing fuel consumption as much as 15%. Basically, the valves are opened by hydraulic pumps, which are operated by the ECU. The valves can open several times per intake stroke, based on engine load. The ECU then decides how much fuel should be injected to optimize combustion.

The elimination of cams, lifters, rockers, and timing set not only reduces weight and bulk, but also friction.

Cylinder deactivation could be made much more fuel efficient if the intake valve could be opened on every down stroke and the exhaust valve opened on every upstroke of the deactivated cylinder. Another even more significant advancement will be the elimination of the convention throttle. When a car is run at part throttle, this interruption in the airflow causes excess vacuum, which causes the engine to use up valuable energy acting as a vacuum pump.

Advantages: Cost of components come down. Engine become smaller in size. More power. Lowest Emissions. Degree of control 1000 times better than

carburetor. Better mileage. A smoother idle and reduced operation

expenses.

Conclusion While electronic engine management is still

a complex undertaking, the results can be worth it for small engine OEM’S seeking an edge in performance, emissions or in minimizing the long-term operating costs of their product. Plenty of application assistance is available from the manufacturer’s of the ECU, fuel-delivery system and sensors needed to implement electronic engine management.

Thank You! Made By-Tanuj

Kumar SID- 12104025

Guided By- Yogesh Sir.