Gasoline electronic Direct Injection System prepared by:

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Gasoline electronic Direct Injection System
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Gasoline electronic Fuel Injection Systems
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Introduction

• A modern gasoline injection system uses pressure
  from an electric fuel pump to spray fuel into the
  engine intake manifold. Like a carburetor, it
  must provide the engine with the correct air-fuel
  mixture for specific operating conditions.    Unli
  ke a carburetor, however, PRESSURE, not engine
  vacuum, is used to feed fuel into the engine.
  This  makes  the  gasoline  injection system
   very  efficient

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

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

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There are many types of gasoline injection
systems. Before studying the most common ones,
you should have A basic knowledge of the
different classifications
single- or multi-point injection
indirect or direct injection
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• The point or location of fuel injection is one
  way to classify a gasoline injection system. A
  single-point injection  system,  also  call
   throttle  body  injection  (TBI), has the
  injector nozzles in a throttle body assembly on
  top of the engine. Fuel is sprayed into the top
  center of the  intake  manifold .

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

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• An indirect injection system
  sprays fuel into the
  engine  intake  manifold.  
  Most  gasoline  injection
  systems are of this
  type.
• Direct injection forces fuel
  into the engine combustion
  chambers. Diesel
  injection systems
  are direct type.
• So
• Gasoline electronic Direct Injection System
  
• is Classified as multi-point and Direct
  injection systems
• 
  

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System component

• Fuel tank
• Electric fuel pump
• Fuel filter
• Electronic control unit
• Common rail and Pressure sensor
• Electronic Injectors
• fuel line

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Fuel tank

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

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

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Electric fuel pump

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

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

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

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Fuel filter

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

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Electronic control unit

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

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Working of ECU

• Control of fuel injection ECU will determine the
  quantity of fuel to inject based on a number of
  parameters. If the throttle pedal is pressed
  further down, this will open the throttle body
  and allow more air to be pulled into the engine.
  The ECU will inject more fuel according to how
  much air is passing into the engine. If the
  engine has not warmed up yet, more fuel will be
  injected .
• 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.

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• Control of idle speed Most engine systems have
  idle speed control built into the ECU. 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.

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Common rail and Pressure sensor

• The term "common rail" refers to the fact that
  all of the fuel injectors are supplied by a
  common fuel rail which is nothing more than a
  pressure accumulator where the fuel is stored at
  high pressure. This accumulator supplies multiple
  fuel injectors with high pressure fuel.

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

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Electronic Injectors

• The injectors can survive the excessive
  temperature and pressure of combustion by using
  the fuel that passes through it as a coolant

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

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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.

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Gasoline direct injection

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

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

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

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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.
• Whats 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.

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• 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
  151 in the vicinity of the sparkplug, the
  mixture will not ignite at all and a miss-fire
  results.

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• 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.

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How much fuel are we injecting here?

• lets 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 its doing very
  close to 2400 rpm or 2400/60 40 revolutions per
  second. Because its a 4 cylinder 4 stroke
  engine, it will be producing 2 power strokes
  every revolution, so thats 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?

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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 (gt29,000
  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 engines 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.