Fuel-system
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12-Sep-2014 -
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Automotive
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Transcript of Fuel-system
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The object of all of the systems is to maintain the optimum air/ fuel mixture, which is chemically correct for theoretically complete combustion.
The stoichiometric ratio is 14.7 :1 (air to fuel).
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Fuel inlet system.
Idle system.
Power enrichment system.
Main metering system.
Cold start system.
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Dictate a more exact control of the engine air/fuel mixture
It generates an electrical signal and sends it to the computer
The need for Better fuel economy The increasingly strict emission control regulations
These systems operate in the following manner:
The oxygen sensor, installed in the exhaust manifold upstream of the catalytic converter, reads the oxygen content of the exhaust- gases.
The computer then decides how to adjust the mixture to. keep it at the correct air/fuel ratio.
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RICH MIXTURE
AMOUNT OF OXYGEN
IN EXHAUST. LOW
HIGH SENSOR VOLTAGE
FREQUENCY VALVE
OPEN\CLOSE RATIO
DECREASING
PRESSURE UNDER DIAPHRAM
INCREASING
LEAN MIXTURE
AMOUNT OF OXYGEN
IN EXHAUST .HIGH
LOW SENSOR VOLTAGE
FREQUENCY VALVE
OPEN\CLOSE RATIO
INCREASING
PRESSURE UNDER DIAPHRAM
DECREASING
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ENGINE EXHAUST
OXYGEN SENSOR
CATALYTIC CONVERTER
ELECTRONIC CONTROL UNIT
THROTTLE BODY
PRESSURE REGULATOR
FILTER
FUEL TANK
RETURN LINE
FUEL CONTROL SYSTEM
E.S
V.S E.
T
M.P
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Conventional Ignition
System is triggered by contact breakers
The ignition coil is switched on and off mechanically
Synchronization with the crankshaft
The vacuum advance mechanism adjusts the ignition timing in relationship to engine load.
The centrifugal advance mechanism adjusts the ignition timing in relation to engine speed.
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Transistorised Ignition
Triggering is done by transistors.
Ignition advance is the same as for the conventional.
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There is no mechanical advance system in the distributor.
Engine speed and proximity sensor is used to trigger the ignition.
The E.C.U. computes the required ignition point and modifies the output signal.
Fully programmed Electronic Ignition
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Fully programmed Electronic Ignition
An ignition advance map is written into the E.C.U.
It permits the best ignition point for any engine speed and load.
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STATIC IGNITION
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Static Ignition
The Static Ignition performs the same functions as the programmed system but has no rotating H.T. distribution system.
A four spark ignition coil is used instead of an ignition distributor
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Static Ignition
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Static Ignition
The two coils, within the four-spark ignition, are energised alternately via the E.C.U.
The respective coil generates two sparks simultaneously
One fires on the power stroke of the cylinder The other at the end of the exhaust stroke of the cylinder.
Ignition output stage, at the correct point for a given cylinder, determined by the E.C.U. ignition map
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CIRCUIT DIAGRAM
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CIRCUIT DIAGRAM
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COIL RESISTANCE
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COIL RESISTANCE
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The Motronic fuel injection system combines the digital control of individual systems such as fuel injection and ignition into a single unit.
From the inputs engine speed (rpm), crankshaft position and temperature (engine and ambient air)) the control unit determines the ideal spark advance and fuel quantity
In this manner, spark advance and fuel quantity is tailored exactly to the engine operating conditions such as idling, part load, full load, warm up, deceleration and transient modes.
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SEMULTANEOUS INJECTION
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SEMI-SEQUENTIAL INJECTION
+12
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SEQUENTIAL INJECTION
+12
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