Engine 2&3 - Fuel System Petrol 2
Petrol injection system
This does not use a carburetor. Here petrol under pressure is spray through an injector nozzle into the inlet manifold
or directly into the cylinder. The primary difference between carburetors and fuel injection is that fuel injection
atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake
air accelerated through a Venturi tube to draw the fuel into the airstream. Fuel injection has several advantages over
carburetor.
Fuel efficiency
Power Output
Emissions performance
Running on alternative fuels
Reliability
Drivability and smooth operation
Initial cost
Maintenance cost
Diagnostic capability
Range of environmental operation
Engine tuning
Type of petrol injection
There are two basic ways of classifying fuel injection system
1. According to where the fuel is injected in the engine.
2. According to the method of injection.
Petrol under pressure can be spray through an injector nozzle into one of three locations.
1. Petrol may be injected into the throttle body at the entrance to the intake manifold.(single point injection or
throttle body injection)
2. Petrol may be injected into the intake manifold just ahead of the intake valve.( multipoint/port injection-
MPI)
3. Petrol may be injected directly in to the cylinder ( Direct injection)
Here, a) and b) are called indirect injection. Most of the engines system based on indirect injection, but the latest
development in petrol injection is the gasoline direct injection system.
1
Eishaka
, Engine 2&3 - Fuel System Petrol 2
Method of injection
There are number of design differences among method of injecting petrol, but they used one of the following three
methods to regulate the quantity of fuel injector.
1. Intermittent injection- Timed
2. Intermittent injection- Non timed
3. Continuous injection
Intermittent injection- Timed
Some fuel injection systems inject fuel ahead of each inlet valve just before/ during intake stroke. This system uses
one injector for each cylinder. Each injector is opened for only several millisecond and is carefully timed to each
cylinder intake stroke. Since the injection take place according to the firing order of the engine, and this method is
also called sequential injection. The injector is open by means of an electric solenoid. When an electric current is
passed through the solenoid winding, it force a powerful magnetic field that lifting needle from its seat. This admits a
stream of fuel for as long as the injector remain energized.
In some systems there is only one injector per engine which is in the entrance to the inlet manifold (throttle body
injection/SPI). The injector is triggered synchronizing with ignition timing.
Intermittent injection- Non timed
A number of petrol injection systems do not attempt to precisely each injection to a specific cylinder intake stroke. In
some systems all the injectors inject fuel at the same time. This method is called simultaneous injection (inject same
time). In this method only, half of the required amount of fuel is injected at a time and the other half later during the
cycle. Therefore there is two injections per 720’ of crankshaft revolution.
Some systems energized one half of the injection all at once. Then entire other half on a alternating basis. Some use
three for four groups. This method is also called group injection. In these non-timed systems, the mixture will remain
in the inlet manifold until the intake strokes drawn in to the cylinder.
Continuous injection
During engine operation, this system feeds atomized fuel from the injector all the time. The amount will vary to suit
the engine needs. The continuous system does not need solenoid to open or closed them. Fuel pump pressure
causes the spring loaded injector open causing fuel to spray into the intake manifold.
GDI - The engine management system continually chooses among three combustion modes: ultra-lean burn,
stoichiometric, and full power output. Each mode is characterized by the air-fuel ratio. The stoichiometric air-fuel
ratio for gasoline is 14.7:1 by weight (mass), but ultra-lean mode can involve ratios as high as 65:1 (or even higher in
some engines, for very limited periods). These mixtures are much leaner than in a conventional engine and reduce
fuel consumption considerably. Modern engine operated a pressure of 200bars.
Beginning of petrol fuel injection
Bosch in 1967 when it introduced the first successful mass-produced electronic fuel injection system for
gasoline engines. It first appeared on the 1967 Volkswagen 1600. This was a mechanical fuel injection
system.
Bosch's first electronic fuel injection system, called Jetronic, was based in part on technology developed by
Bendix Corp. It used an early computer and sensors to measure airflow and air temperature.
In 1979, Bosch introduced the next generation of Jetronic, called Motronic. It tied the ignition and gasoline
injection into one central control unit. This is also called engine management system.
In 1995, Bosch introduced electronic throttle control (Motronic). This is called drive by wire system, which
eliminates use of throttle cable.
Latest fuel injections systems are Mono point, Mono Motronic, ,LE-Jetronic, Motronic ME7, Motronic MED.
2
Eishaka
Petrol injection system
This does not use a carburetor. Here petrol under pressure is spray through an injector nozzle into the inlet manifold
or directly into the cylinder. The primary difference between carburetors and fuel injection is that fuel injection
atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake
air accelerated through a Venturi tube to draw the fuel into the airstream. Fuel injection has several advantages over
carburetor.
Fuel efficiency
Power Output
Emissions performance
Running on alternative fuels
Reliability
Drivability and smooth operation
Initial cost
Maintenance cost
Diagnostic capability
Range of environmental operation
Engine tuning
Type of petrol injection
There are two basic ways of classifying fuel injection system
1. According to where the fuel is injected in the engine.
2. According to the method of injection.
Petrol under pressure can be spray through an injector nozzle into one of three locations.
1. Petrol may be injected into the throttle body at the entrance to the intake manifold.(single point injection or
throttle body injection)
2. Petrol may be injected into the intake manifold just ahead of the intake valve.( multipoint/port injection-
MPI)
3. Petrol may be injected directly in to the cylinder ( Direct injection)
Here, a) and b) are called indirect injection. Most of the engines system based on indirect injection, but the latest
development in petrol injection is the gasoline direct injection system.
1
Eishaka
, Engine 2&3 - Fuel System Petrol 2
Method of injection
There are number of design differences among method of injecting petrol, but they used one of the following three
methods to regulate the quantity of fuel injector.
1. Intermittent injection- Timed
2. Intermittent injection- Non timed
3. Continuous injection
Intermittent injection- Timed
Some fuel injection systems inject fuel ahead of each inlet valve just before/ during intake stroke. This system uses
one injector for each cylinder. Each injector is opened for only several millisecond and is carefully timed to each
cylinder intake stroke. Since the injection take place according to the firing order of the engine, and this method is
also called sequential injection. The injector is open by means of an electric solenoid. When an electric current is
passed through the solenoid winding, it force a powerful magnetic field that lifting needle from its seat. This admits a
stream of fuel for as long as the injector remain energized.
In some systems there is only one injector per engine which is in the entrance to the inlet manifold (throttle body
injection/SPI). The injector is triggered synchronizing with ignition timing.
Intermittent injection- Non timed
A number of petrol injection systems do not attempt to precisely each injection to a specific cylinder intake stroke. In
some systems all the injectors inject fuel at the same time. This method is called simultaneous injection (inject same
time). In this method only, half of the required amount of fuel is injected at a time and the other half later during the
cycle. Therefore there is two injections per 720’ of crankshaft revolution.
Some systems energized one half of the injection all at once. Then entire other half on a alternating basis. Some use
three for four groups. This method is also called group injection. In these non-timed systems, the mixture will remain
in the inlet manifold until the intake strokes drawn in to the cylinder.
Continuous injection
During engine operation, this system feeds atomized fuel from the injector all the time. The amount will vary to suit
the engine needs. The continuous system does not need solenoid to open or closed them. Fuel pump pressure
causes the spring loaded injector open causing fuel to spray into the intake manifold.
GDI - The engine management system continually chooses among three combustion modes: ultra-lean burn,
stoichiometric, and full power output. Each mode is characterized by the air-fuel ratio. The stoichiometric air-fuel
ratio for gasoline is 14.7:1 by weight (mass), but ultra-lean mode can involve ratios as high as 65:1 (or even higher in
some engines, for very limited periods). These mixtures are much leaner than in a conventional engine and reduce
fuel consumption considerably. Modern engine operated a pressure of 200bars.
Beginning of petrol fuel injection
Bosch in 1967 when it introduced the first successful mass-produced electronic fuel injection system for
gasoline engines. It first appeared on the 1967 Volkswagen 1600. This was a mechanical fuel injection
system.
Bosch's first electronic fuel injection system, called Jetronic, was based in part on technology developed by
Bendix Corp. It used an early computer and sensors to measure airflow and air temperature.
In 1979, Bosch introduced the next generation of Jetronic, called Motronic. It tied the ignition and gasoline
injection into one central control unit. This is also called engine management system.
In 1995, Bosch introduced electronic throttle control (Motronic). This is called drive by wire system, which
eliminates use of throttle cable.
Latest fuel injections systems are Mono point, Mono Motronic, ,LE-Jetronic, Motronic ME7, Motronic MED.
2
Eishaka
