A gasoline direct injection system uses an electric fuel pump to pressurize fuel and spray it directly into engine cylinders. An electronic control unit controls the fuel injectors and monitors various sensors to precisely meter fuel delivery. A common rail distributes high-pressure fuel from the pump to the electronic injectors, which spray fuel into the combustion chambers when activated by the ECU. This allows for improved efficiency and engine performance compared to earlier fuel injection systems.

1. Gasoline electronic Direct Injection SystemGasoline electronic Direct Injection System
prepared by:prepared by:
•
•
•
•
•
•
•

2. Gasoline electronic Fuel InjectionGasoline electronic Fuel Injection
SystemsSystems

3. IntroductionIntroduction
A modern gasoline injection system uses pressureA modern gasoline injection system uses pressure
from an electric fuel pump to spray fuel into thefrom an electric fuel pump to spray fuel into the
engineengine intake manifold. Like a carburetor, it mustintake manifold. Like a carburetor, it must
provide theprovide the engine with the correct air-fuelengine with the correct air-fuel
mixture for specificmixture for specific operatingoperating
conditions. Unlike a carburetor, howeverconditions. Unlike a carburetor, however,,
PRESSURE, not engine vacuum, is used to feedPRESSURE, not engine vacuum, is used to feed
fuelfuel into the engineinto the engine.. This makes the gasolineThis makes the gasoline
injection injection system very efficientsystem very efficient

4. A gasoline injection system has severalA gasoline injection system has several
possible advantages over a carburetorpossible advantages over a carburetor
type of fuel system. type of fuel system.
Some advantages are as followsSome advantages are as follows::
* Improved atomization. Fuel is forced into the* Improved atomization. Fuel is forced into the
intake manifold under pressure that helps breakintake manifold under pressure that helps break
fuel droplets into a fine mist.fuel droplets into a fine mist.
* Better fuel distribution. Equal flow of fuel vapors* Better fuel distribution. Equal flow of fuel vapors
into each cylinder. into each cylinder.
* Smoother idle. Lean fuel mixture can be used* Smoother idle. Lean fuel mixture can be used
without rough idle because of better fuelwithout rough idle because of better fuel
distribution and low-speed atomization.distribution and low-speed atomization.

5. * Lower emissions. Lean efficient air-fuel* Lower emissions. Lean efficient air-fuel
mixture reduces exhaust pollution. mixture reduces exhaust pollution.
* Better cold weather drivability. Injection* Better cold weather drivability. Injection
provides better control of mixture enrichmentprovides better control of mixture enrichment
than a carburetor.than a carburetor.
* Increased engine power. Precise metering of* Increased engine power. Precise metering of
fuel to each cylinder and increased air flow canfuel to each cylinder and increased air flow can
result in more horsepower output.result in more horsepower output.
* Fewer parts. Simpler, late model, electronic fuel* Fewer parts. Simpler, late model, electronic fuel
injection system have fewer parts thaninjection system have fewer parts than
modern computer-controlled carburetors. modern computer-controlled carburetors.

6. There are many types of gasoline injectionThere are many types of gasoline injection
systems. Before studying the mostsystems. Before studying the most
common ones, you should havecommon ones, you should have ::
A basic knowledge of the different classificationsA basic knowledge of the different classifications ::
** single- or multi-point injectionsingle- or multi-point injection
* indirect or direct injection* indirect or direct injection

7. • The point or location of fuel injection is one way toThe point or location of fuel injection is one way to
classify a gasoline injection system. A single-pointclassify a gasoline injection system. A single-point
injection system, also call throttle body injectioninjection system, also call throttle body injection
(TBI), has the injector nozzles in a throttle body (TBI), has the injector nozzles in a throttle body
assembly on top of the engine. Fuel is sprayed intoassembly on top of the engine. Fuel is sprayed into
the top center of the intake manifoldthe top center of the intake manifold ..

8. • A multi-point injection system, also called portA multi-point injection system, also called port
injection, has an injector in the port (air-fuel passage)injection, has an injector in the port (air-fuel passage)
going to each cylinder. Gasoline is sprayed into eachgoing to each cylinder. Gasoline is sprayed into each
intake port and toward each intake valve. Thereby, theintake port and toward each intake valve. Thereby, the
term multipoint (more than one location) fuelterm multipoint (more than one location) fuel
injection is used. injection is used.

9. • An indirect injection systemAn indirect injection system
sprays fuel into the engine intake manifold. sprays fuel into the engine intake manifold.
Most gasoline injectionMost gasoline injection
systems are of this type.systems are of this type.
• Direct injection forces fuel intoDirect injection forces fuel into
the engine combustion chambers.the engine combustion chambers.
Diesel injection systems are directDiesel injection systems are direct
type.type.
SoSo
Gasoline electronic Direct Injection SystemGasoline electronic Direct Injection System
is Classified asis Classified as :: multi-point and Direct injection systemsmulti-point and Direct injection systems

11. System componentSystem component ::
• Fuel tankFuel tank
• Electric fuel pumpElectric fuel pump
• Fuel filterFuel filter
• Electronic control unitElectronic control unit
• Common rail andCommon rail and Pressure sensor
• ElectronicElectronic Injectors
• fuel line

12. Fuel tankFuel tank
• is safe container for flammable liquids andis safe container for flammable liquids and
typically part of an engine system in which thetypically part of an engine system in which the
fuel is stored and propelled (fuel pump) orfuel is stored and propelled (fuel pump) or
released (pressurized gas) into an engine.released (pressurized gas) into an engine.
• Typically, a fuel tank must allow or provide theTypically, a fuel tank must allow or provide the
following:following:
* Safe (UL Approved) fuel storage, there is some* Safe (UL Approved) fuel storage, there is some
concern that UL (Underwriters Laboratories) isconcern that UL (Underwriters Laboratories) is
not the final arbiter of safety.not the final arbiter of safety.
* Filling (the fuel tank must be filled in a secure* Filling (the fuel tank must be filled in a secure
way) No Sparks.way) No Sparks.
* Storage of fuel (the system must contain a given* Storage of fuel (the system must contain a given
quantity of fuel and must avoid leakage and limitquantity of fuel and must avoid leakage and limit
evaporative emissions)evaporative emissions)

13. * Provide a method for determining level of fuel in tank,* Provide a method for determining level of fuel in tank,
Gauging (the remaining quantity of fuel in the tankGauging (the remaining quantity of fuel in the tank
must be measured or evaluated)must be measured or evaluated)
* Venting (if over-pressure is not allowed, the fuel vapors* Venting (if over-pressure is not allowed, the fuel vapors
must be managed through valves)must be managed through valves)
* Feeding of the engine (through a pump)* Feeding of the engine (through a pump)
* Anticipate potentials for damage and provide safe* Anticipate potentials for damage and provide safe
survival potential.survival potential.

14. Electric fuel pumpElectric fuel pump
• An electric fuel pump is used on engines with fuelAn electric fuel pump is used on engines with fuel
injection to pump fuel from the tank to the injectors.injection to pump fuel from the tank to the injectors.
The pump must deliver the fuel under high pressureThe pump must deliver the fuel under high pressure
(typically 30 to 85 psi depending on the application) so(typically 30 to 85 psi depending on the application) so
the injectors can spray the fuel into the engine.the injectors can spray the fuel into the engine.
• Electric fuel pumps are usually mounted inside the fuelElectric fuel pumps are usually mounted inside the fuel
tank,tank,
• Some vehicles may even have two fuel pumps (aSome vehicles may even have two fuel pumps (a
transfer pump inside the tank, and a main fuel pumptransfer pump inside the tank, and a main fuel pump
outside).outside).

15. • Electric fuel pumps come in a variety of designs.Electric fuel pumps come in a variety of designs.
Some older applications use a positive displacementSome older applications use a positive displacement
"roller cell" pump. This type uses rollers mounted on"roller cell" pump. This type uses rollers mounted on
an offset disc that rotates inside a steel ring. Fuel isan offset disc that rotates inside a steel ring. Fuel is
drawn into the spaces (cells) between the rollers anddrawn into the spaces (cells) between the rollers and
pushed along from the pump inlet to the outlet. Thispushed along from the pump inlet to the outlet. This
type of pump can generate very high pressure, andtype of pump can generate very high pressure, and
the flow rate tends to be constant. But the outputthe flow rate tends to be constant. But the output
comes in pulses, so a muffler is often mounted in thecomes in pulses, so a muffler is often mounted in the
fuel line after the pump to dampen pressure pulses. Afuel line after the pump to dampen pressure pulses. A
roller cell pump may also be mounted outside the fuelroller cell pump may also be mounted outside the fuel
tank, and used with a second low pressure supplytank, and used with a second low pressure supply
pump mounted inside the fuel tank.pump mounted inside the fuel tank.

16. • Most newer vehicles use a "turbine" style fuel pump. AMost newer vehicles use a "turbine" style fuel pump. A
turbine pump has an impeller ring attached to theturbine pump has an impeller ring attached to the
motor. The blades in the impeller push the fuelmotor. The blades in the impeller push the fuel
through the pump as the impeller spins. This type ofthrough the pump as the impeller spins. This type of
pump is not a positive-displacement pump, so itpump is not a positive-displacement pump, so it
produces no pulsations, runs very smoothly andproduces no pulsations, runs very smoothly and
quietly. It is also less complicated to manufacture andquietly. It is also less complicated to manufacture and
is very durable. Some aftermarket pump supplies useis very durable. Some aftermarket pump supplies use
this type of pump to replace the older designs.this type of pump to replace the older designs.

17. Fuel filterFuel filter
• The fuel filter is the fuel system's primary line ofThe fuel filter is the fuel system's primary line of
defense against dirt, debris and small particles of rustdefense against dirt, debris and small particles of rust
that flake off the inside of the fuel tank .that flake off the inside of the fuel tank .
• many filters for fuel injected engines trap particles asmany filters for fuel injected engines trap particles as
small as 10 to 40 microns in size.small as 10 to 40 microns in size.
• fuel filter normally made intofuel filter normally made into
cartridges containing a filter paper.cartridges containing a filter paper.

18. Electronic control unitElectronic control unit
• In automotive electronics,In automotive electronics, electronic control unitelectronic control unit
((ECUECU) is a generic term for any embedded system) is a generic term for any embedded system
that controls one or more of the electrical systems orthat controls one or more of the electrical systems or
subsystems in a motor vehicle.subsystems in a motor vehicle.
• AnAn engine control unit (ECU)engine control unit (ECU) , also known as, also known as
power-train control module (PCM)power-train control module (PCM) , or, or engineengine
control module (ECM)control module (ECM) is a type of electronicis a type of electronic
control unit that determines the amount of fuel, ignitioncontrol unit that determines the amount of fuel, ignition
timing and other parameters an internal combustiontiming and other parameters an internal combustion
engine needs to keep running. It does this by readingengine needs to keep running. It does this by reading
values from multidimensional maps which containvalues from multidimensional maps which contain
values calculated by sensor devices monitoring thevalues calculated by sensor devices monitoring the
engine.engine.

19. Working of ECUWorking of ECU
• Control of fuel injection:Control of fuel injection: ECU will determine theECU will determine the
quantity of fuel to inject based on a number ofquantity of fuel to inject based on a number of
parameters. If the throttle pedal is pressed furtherparameters. If the throttle pedal is pressed further
down, this will open the throttle body and allow moredown, this will open the throttle body and allow more
air to be pulled into the engine. The ECU will injectair to be pulled into the engine. The ECU will inject
more fuel according to how much air is passing intomore fuel according to how much air is passing into
the engine. If the engine has not warmed up yet, morethe engine. If the engine has not warmed up yet, more
fuel will be injected .fuel will be injected .
• Control of ignition timing :Control of ignition timing : A spark ignition engineA spark ignition engine
requires a spark to initiate combustion in therequires a spark to initiate combustion in the
combustion chamber. An ECU can adjust the exactcombustion chamber. An ECU can adjust the exact
timing of the spark (called ignition timing) to providetiming of the spark (called ignition timing) to provide
better power and economy.better power and economy.

20. • Control of idle speedControl of idle speed :: Most engine systems haveMost engine systems have
idle speed control built into the ECU. The engine RPMidle speed control built into the ECU. The engine RPM
is monitored by the crankshaft position sensor whichis monitored by the crankshaft position sensor which
plays a primary role in the engine timing functions forplays a primary role in the engine timing functions for
fuel injection, spark events, and valve timing. Idlefuel injection, spark events, and valve timing. Idle
speed is controlled by a programmable throttle stop orspeed is controlled by a programmable throttle stop or
an idle air bypass control stepper motor.an idle air bypass control stepper motor.

21. Common rail andCommon rail and Pressure
sensor
• The term "common rail" refers to the fact that all of theThe term "common rail" refers to the fact that all of the
fuel injectors are supplied by a common fuel rail whichfuel injectors are supplied by a common fuel rail which
is nothing more than a pressure accumulator whereis nothing more than a pressure accumulator where
the fuel is stored at high pressure. This accumulatorthe fuel is stored at high pressure. This accumulator
supplies multiple fuel injectors with high pressure fuel.supplies multiple fuel injectors with high pressure fuel.

22. • The fuel injectors are typically ECU-controlled.The fuel injectors are typically ECU-controlled.
When the fuel injectors are electrically activated aWhen the fuel injectors are electrically activated a
hydraulic valve (consisting of a nozzle and plunger)hydraulic valve (consisting of a nozzle and plunger)
is mechanically or hydraulically opened and fuel isis mechanically or hydraulically opened and fuel is
sprayed into the cylinders at the desired pressure.sprayed into the cylinders at the desired pressure.
Since the fuel pressure energy is stored remotelySince the fuel pressure energy is stored remotely
and the injectors are electrically actuated theand the injectors are electrically actuated the
injection pressure at the start and end of injection isinjection pressure at the start and end of injection is
very near the pressure in the accumulator (rail), thusvery near the pressure in the accumulator (rail), thus
producing a square injection rate. If the accumulator,producing a square injection rate. If the accumulator,
pump, and plumbing are sized properly, the injectionpump, and plumbing are sized properly, the injection
pressure and rate will be the same for each of thepressure and rate will be the same for each of the
multiple injection events.multiple injection events.

24. ElectronicElectronic Injectors
• The injectors can survive the excessive temperatureThe injectors can survive the excessive temperature
and pressure of combustion by using the fuel thatand pressure of combustion by using the fuel that
passes through it as a coolantpasses through it as a coolant

25. • The electronic fuel injector is normally closed, andThe electronic fuel injector is normally closed, and
opens to inject pressurized fuel as long as electricity isopens to inject pressurized fuel as long as electricity is
applied to the injector's solenoid coil.applied to the injector's solenoid coil.
• When the injector is turned on, it opens, sprayingWhen the injector is turned on, it opens, spraying
atomized fuel at the combustion chamber .atomized fuel at the combustion chamber .
• Depending on engine operating condition ,injectionDepending on engine operating condition ,injection
quantity will vary .quantity will vary .

26. fuel line
• Fuel line hoses carry gasoline from the tank to
the fuel pump, to the fuel filter, and to the fuel
injection system. While much of the fuel lines are
rigid tube, sections of it are made of rubber
hose, which absorb engine and road vibrations.
• There are two basic types of fuel hose: Fuel and
oil hoses that meet the SAE 30R7 standard, and
fuel injection hose that meets the requirements
of SAE 30R9.

27. Gasoline direct injectionGasoline direct injection
• In internal combustion engines,In internal combustion engines, gasolinegasoline
direct injectiondirect injection is a variant of fuel injectionis a variant of fuel injection
employed in modern two- and four- stroke petrolemployed in modern two- and four- stroke petrol
engines. The petrol/gasoline is highlyengines. The petrol/gasoline is highly
pressurized, and injected via a common rail fuelpressurized, and injected via a common rail fuel
line directly into the combustion chamber ofline directly into the combustion chamber of
each cylinder, as opposed to conventional multi-each cylinder, as opposed to conventional multi-
point fuel injection that happens in the intakepoint fuel injection that happens in the intake
tract, or cylinder port.tract, or cylinder port.

28. How system work:How system work:

29. • When the driver turns the ignition key on,When the driver turns the ignition key on,
the power train control module (PCM)the power train control module (PCM)
energizes a relay that supplies voltage toenergizes a relay that supplies voltage to
the fuel pump. The motor inside the pumpthe fuel pump. The motor inside the pump
starts to spin and runs for a few secondsstarts to spin and runs for a few seconds
to build pressure in the fuel system. Ato build pressure in the fuel system. A
timer in the PCM limits how long the pumptimer in the PCM limits how long the pump
will run until the engine starts.will run until the engine starts.
• Fuel is drawn into the pump through anFuel is drawn into the pump through an
inlet tube and mesh filter sockinlet tube and mesh filter sock
• The fuel then exits the pump through aThe fuel then exits the pump through a
one-way check valve and is pushedone-way check valve and is pushed
toward the engine through the fuel linetoward the engine through the fuel line
and filter.and filter.

30. • The fuel filter traps any rust, dirt or other solidThe fuel filter traps any rust, dirt or other solid
contaminants that may have passed throughcontaminants that may have passed through
the pump to prevent such particles fromthe pump to prevent such particles from
clogging the fuel injectors.clogging the fuel injectors.
• The fuel then flows to the fuel supply rail on theThe fuel then flows to the fuel supply rail on the
engine and is routed to the individual fuelengine and is routed to the individual fuel
injectors. A fuel pressure regulator on the fuelinjectors. A fuel pressure regulator on the fuel
rail maintains fuel pressure, and recirculatesrail maintains fuel pressure, and recirculates
excess fuel back to the tank.excess fuel back to the tank.
• The fuel pump runs continuously once theThe fuel pump runs continuously once the
engine starts, and continues to run as long asengine starts, and continues to run as long as
the engine is running and the ignition key is on.the engine is running and the ignition key is on.
If the engine stalls, the (PCM) will detect theIf the engine stalls, the (PCM) will detect the
loss of the RPM signal and turn the pump off.loss of the RPM signal and turn the pump off.

31. Finally :Finally :
• what is Fuel Injection? it describes the way the
fuel (usually a liquid fuel) is injected (pumped
under pressure) into some part of the engine
where it can combine with the air charge in the
cylinders and combustion can take place,
releasing energy to propel the vehicle.
• What’s different about diesel [CI] engine injection?
Diesel (compression ignition or CI ) and petrol/gasoline
(spark ignition or SI ) engines go about the task of
releasing energy from their fuels in quite different
ways.

32. • In fuel-injected spark ignition [SI] engines, fuel is
always injected into the air charge well before ignition
takes place. This necessary because the liquid or
gaseous fuel must be thoroughly mixed together with
air into a combustible mixture, able to be ignited by the
electrical arc generated by the sparkplug. If the ratio of
air to fuel is not reasonably close to 15:1 in the vicinity
of the sparkplug, the mixture will not ignite at all and a
miss-fire results.

33. • Compression ignition [CI] engines always inject the fuel charge
directly into a combustion chamber in the engine. Fuel injection
and ignition are inextricably tied together in compression
ignition [CI] engines. Recall that CI engines only work because
they compress the air charge so that it is hot enough to
instantly ignite the fuel charge as it is being injected. The
combustion of the fuel begins at the instant it begins being
injected (well, within a couple of milliseconds, if you want to split
hairs) into the combustion chamber full of very hot air (more
than 400 ºC, often over 700 ºC).
• This means the timing of ignition is intimately tied to the fuel
injection process. So, the fuel injection system of a CI engine is
responsible for regulating both the quantity of fuel to be injected
and timing of the beginning of combustion. Many ingenious
techniques have been developed to achieve both these tasks
with admirable accuracy, long before the advent of
sophisticated electronic controls.

34. How much fuel are we injecting here?
• let’s do a few simple sums based on 1997 Land Rover
Discovery. It has a 4 cylinder 2.5 liter engine. At 100 km/h in 5th
gear it’s doing very close to 2400 rpm or 2400/60 = 40
revolutions per second. Because it’s a 4 cylinder 4 stroke
engine, it will be producing 2 power strokes every revolution, so
that’s 80 power strokes per second. At a steady cruising speed
of 100 km/h, it is likely to be covering 10 km/liter or, in other
words, using 10 litres/100 km. Therefore, our fuel burn rate is
10 liters per hour or 10/3600 = 0.00278 liters per second = 2.78
mL/sec. Now, this 2.78 mL is shared between the 80 power
strokes of the engine per second. So, for each power stroke of
the engine while we are cruising at 100 km/h, the fuel injection
system is delivering 2.78/80 = 0.03472 mL into each cylinder.
Not much is it? And the injection system delivers precisely this
quantity of fuel to one of the cylinders of the engine, 80 times
per second and at the exact instant the cylinder needs to fire.
Not bad for a completely mechanical system with no electronic
“smarts” at all, is it?

35. How much
pressure?• SI engine (petrol/gasoline) injection systems typically run at
pressure of 2 to 3 bar (30 to 40 psi). In contrast CI (diesel)
engines employ injection pressures of at least 350 bar (~5000
psi) and possibly in excess of 2000 bar (>29,000 psi) – quite a
bit different to petrol/gasoline systems! This explains why CI
injection systems are so solidly built and piped-up with strong
steel tubing, etc.
• Petrol/gasoline readily vaporizes in the air stream entering the
engine’s cylinders and in contact with the hot cylinder head
surfaces, to form an easily ignitable air/vapor mixture. On the
other hand, to instantly ignite the much less volatile diesel fuel
in the hot air charge of a CI engine it is necessary to spray it
into the combustion chamber in extremely small droplets. And
to achieve this, extremely high injection pressures are required
– the higher the better, in general.