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Electronic Engine Management
Purpose of EEM:
F Controlling of Engine operation electronically by electronic components.
F Benefits to the motorist, more power, better mileage, a smoother idle and reduced operation expenses.
F Cost of components come down.
F Engine become smaller in size.
1. Electronic Control Module
2. Fuel Delivery System
3. Ignition System
Electronic Control Module:
F It is a extremely reliable piece of hardware.
F It process information hundreds of times per second.
F It is actually a microprocessor.
F It is programmed by the Manufacturer.
F It controls the fuel delivery and ignition timing by receiving information from sensors.
Fuel Delivery system
F The fuel line passes through which feeds each injector and it passes through a pressure regulator.
F The surplus fuel heading 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.
F This fuel delivery system is controlled by ECU to provide lean and rich mixtures depending on operating conditions.
F To maximize the Engine output, spark should be at the precise moment.
F Maximum combustion chamber pressure can be attained.
F A mechanical advance distributor is used for this.
F A spark advance map is developed and stored in the ECU.
F As the speed increases, the spark should be advanced further.
1 Throttle Position Sensor
F The ECU senses how wide the throttle is opened.
F The ECU controls fuel delivery and spark timing.
F It consists of a wiper arm and resistor.
F At idle, resistance is high, Voltage is .6-.9v.
F As throttle presses, resistance decreases, voltage is 3.5-4.7v.
2. Exhaust gas oxygen sensor:
F It is placed in Engine’s exhaust system.
F Consists of Zirconium Dioxide cell, provide precise indication of stoichiometric A/F ratio.(14.7:1).
F Zirconium Dioxide is the outer cell exposed to exhaust gas and inner electrode is exposed to ambient air.
F The output varies from 0v-1v.
F At stoichiometric point it produces .45v
F It provides precise output voltage measurements.
F It senses the degree of vacuum in the engine intake manifold.
F Vacuum decreases when throttle is opened/engine are under load.
F A silicon chip (piezoelectric) is provided with a reference pressure one side.
F Pressure to be measured is applied on the other side.
F Variation in pressure causes change in resistance of the silicon chip.
F It covers the amount of air drawn into voltage.
F ECU senses it and calculates the engine load.
F It is located at the intake air stream, between the air cleaner and throttle body. Coolant temperature sensor:
F ECU Senses the temperature and decides whether to activate/deactivate the cooling fans in water cooled engines.
F It helps to enrich the mixture for cold starting, and provide lean mixtures for fuel economy.
F It directly gives the engine operating temperature.
F It is located on the coolant passage.
F It Consists of a fixed value resistor, supplied with 5V.
F ECU Senses the change in voltage between the temperature sensor and the fixed value resistor.
F When the sensor is cold, resistance is high and voltage is increases.
F As the temperature increases, the sensor resistance and the voltage decreases.
F It detects the engine knock occurs during combustion process, it is located in the engine block.
F Engine knocks within a specific frequency range.
F It is a piezoelectric element, generates a voltage when a pressure or vibration is applied.
Throttle and timing sensor:
F It provides the information about how fast the engine is running or where the crankshaft is in its rotation.
F ECU senses this information and adjusts the fuel injection and the spark timing so that the engine speed does not exceed the safe operating limits.
F These sensors use a target wheel with a missing or odd-shaped gear tooth to provide the reference position.
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