Basic EFI by IoD26Xu

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									Basic EFI
                  Layout
                 Diaphragm                          Spring


                                                     Manifold
Injectors                                            Vacuum



                                         Seat
                         Pintle


                             Fuel Pump          Return Line
            Fuel Tank
       ECM Controls
To determine the amount of fuel
required, the ECM needs to know how
much air is entering the engine
Two methods for measuring airflow
 Speed-Density
 Mass Airflow
      Speed-Density
The ECM receives input from
 MAP (engine vacuum)
 TPS (throttle position)

 CTS (coolant temperature)

 IAT (air temperature)

 O2 (rich/lean indicator)

 CKP (engine RPM)
        Speed-Density
Based on the engine vacuum, engine rpm,
intake air temperature, and the pre-
programmed volumetric efficiency of the
engine, the computer calculates the amount
of air entering the engine
Engine operating temperature, throttle
position, and rich/lean indications from the O2
are then used to calculate/adjust the required
amount of fuel
            Speed Density
                              O2     CTS   TPS


MAP
                  ECM   Airflow    ECM
CKP

IAT



      Injectors
        Mass Airflow
Based on the airflow data received from
the MAF engine operating temperature,
throttle position, and rich/lean
indications from the O2 are used to
calculate/adjust the required amount of
fuel
Mass Airflow                  O2     CTS   TPS

                                                 CKP

                  ECM   Airflow    ECM
MAF




      Injectors
          Fuel Injectors
Solenoid type
  ECM controls the ground side of the injector circuit

Poppet type
  When pressure reaches a predetermined level the
   injector is forced open
  Diesel, CFI, CIS
Types of Fuel Injection
Throttle Body Injection (TBI)
Port Fuel Injection (PFI) (MPFI)
Central Point Injection (CPI)
Gasoline Direct Injection (GDI)
Constant Injection System (CIS)
Different manufacturers may call similar
systems by different names
Throttle Body Injection
         (TBI)
The throttle body looks similar to a carburetor
The throttle body contains the fuel injectors and
usually the pressure regulator
Pressure regulator does not use vacuum to cut back
fuel pressure during high vacuum conditions
    Port Fuel Injection
Throttle body only controls the amount of air entering
the engine
Injectors are located in each intake port
  One injector per cylinder
May use an additional cold start injector
Intake manifold only has to deliver air therefore
problems with fuel puddling are greatly reduced
Injectors may be batch fired or sequentially fired (SFI)
Tuned port injection operates the same as port fuel
injection, except the intake manifold is designed for
optimal cylinder filling
Port Fuel Injection
Port Fuel Injection
Port Fuel Injection
  (Batch Fired)
Cold Start Injector
     Central Point Fuel
         Injection
Used on GM Vortec engines
Central injection assembly located in the lower intake
Fuel flow controlled by electric solenoids in the CPI
assembly
May be batch fired or sequentially fired
Pressure regulator located in the CPI assembly
Actual fuel injectors are mechanical
  Won’t open unless the specified fuel pressure is
   present
Operates at a relatively high fuel pressure (55-61
PSI)
Central Point Fuel
    Injection
Central Point Fuel
    Injection




 Poppet Injector
                Central Point Fuel
                    Injection
                              CPI Assembly
Pressure Line




                                  ECM Actuated
                                  Solenoid-type
                                  Injectors

Return Line     Pressure       Poppet Injectors
                Regulator
   Constant Injection
     System (CIS)
Mechanical injection system
Used extensively by the Germans
Amount of fuel delivered is controlled by
altering fuel pressure at the injector
rather that injector on time
Uses a air vane to sense engine airflow
and change fuel delivery rates
         Constant Injection
              System
Mechanical
Injector
                  Metering
                   Valve      Differential
                              Pressure Valve

                                               Filter




                                                        Pump

       Air Vane              Pressure           Tank
                             Regulator
Constant Injection
 System (CIS-E)
    Idle Speed Control
In EFI systems the ECM controls idle
speed
 Throttle opening control
 Throttle Air Bypass
     To increase idle speed, more air is bypassed
      by the throttle blades
     To decrease idle speed, less air is bypassed by
      the throttle blades
IDLE SPEED CONTROL
To comply with federal emissions
standards, idle speed control systems
are used
Idle speed controlled by electronic
module
Earlier systems, engines idled in open
loop
Idle systems depend on inputs to PCM
    Throttle Kicker
 controlled by Vacuum
      Diaphragm




Electrically controlled by solenoid
Operates during engine warm up, with air
conditioning on and engine overheating
Some act as a dashpot
                                           327C
Throttle Kicker and Idle
     Stop Solenoid
             Electrically
             controlled
             Vacuum operated
             throttle kicker for
             additional load
             Allows curb idle
             speed to be lower
             Controlled by PCM
             Must be adjusted
     327C
IDLE SPEED CONTROL
    MOTOR (ISC)
          PCM controlled
          Reversible gear
          drive dc motor
          PCM reverses
          polarity
          Has idle tracking
          switch
  325C    Must be adjusted
ISC Schematic
  IDLE AIR CONTROL
         (IAC)
Used with Fuel
Injection systems
PCM controlled
Stepper motor
Diverts air around
throttle plate
Do not over extend
when replacing
Not adjustable
Throttle Body IAC
    Location
          Screws into throttle
          body
          Must be careful to
          not over-tighten
          Must keep passages
          clean
          Can use Scanner to
          diagnose idle
          problems
                                       508L

      IAC SCHEMATIC




Contains two motor windings
Can test with ohmmeter (GM are 40 - 80 ohms)
Use IAC Test tool to check operation
Can monitor operation with Scanner
IAC SCOPE PATTERNS
          Typical patterns
          Compare patterns to
          known good patterns
          Some IAC’s operate on
          12 volts and others on
          less voltage
          IAC operates with a
          duty cycle
  ADJUSTING CURB IDLE
(Idle Hardstop or Minimum
        Idle speed)
Minimum idle rpm is
factory adjusted
Idle must be
adjusted correctly
Passages must be
clean
Some systems, you
must adjust TPS
also
                      502L
 IDLE SPEED
ADJUSTMENT
      Must shut off idle air
      to adjust minimum
      idle speed
      Use idle plug on TBI
      units
      Other systems, you
      just turn a screw to
      control air flow (idle
      rpm)
Ford Pulse Width Idle Control
  Motor (Bypass Air Valve)
Depending on the % on time form the
ECM the pulse width motor allows more
or less air to bypass the throttle blades

      ICM

                   Throttle
                   Body
 Intake

								
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