It’s not complicated, but there are a lot of details...
•  EFI Introduction
•  Background and Theory
•  Hardware Components
•  Ways to Retrofit EFI
•  Examples

General Perspective.
Internal Combustion Engines are reactors which combine air and fuel to produce heat and energy. We can control them to deftly and efficiently use the fuel and produce energy as we wish. We accomplish this by how we fuel the engines.

Fueling needs for an engine.
•  Right Mixture (ratio) of oxygen and fuel
   •  not lean or rich
   •  air fuel ratio called AFR
•  Right total amount of correct mixture
   •  small amount at idle
   •  larger amounts under load

The Common Control Strategy For Fueling Engines.
•  Control/limit the amount of air (oxygen) entering into the engine
•  Add correct amount of fuel for that amount of air (oxygen)
   Result: the right ratio of air and fuel and the right total amount of mixture

How To Limit Oxygen Intake.
•  Restrict Air (20% Oxygen) Flow into engine
      Throttle Plate Cheap, Easy, common
      Variable Regulator Expensive

Ways to Add Fuel.
•  Use Physical Forces Directly (Carb)
•  Use Electronic Devices (EFI)
•  Use measurements and calculations to define the amount of fuel to use for ignition event
•  Squirt the fuel into the airstream entering the engine

Carb Fueling.
•  Use the inrush of air to get the right amount of fuel into the motor (Bernoulli effect)
•  Constant Velocity variable venturi (SU, etc)
•  Variable Velocity constant venturi (Holley)
•  Pretty good & cheap, Can Look ‘Cool’ but Not very accurate or flexible
•  Less power and more pollution
•  Lower engine life

EFI Fueling Strategy.
•  Measure the amount of air going into the engine
•  Calculate the right amount of fuel
•  Inject the right amount of fuel for each combustion event (from dizzy or crank)
•  Car Runs better, cleaner, more reliably
•  Flexible Tuning

Measure the Amount of Air for Each Combustion Event.
•  MAP: Air pressure and Cylinder volume defines the amount of oxygen going into the motor, so just measure manifold pressure (vacuum) (simpler, more reliable) and use cylinder volume to calculate
•  MAF: measure mass of air going into motor directly. (first, still used)

Calculate the Right Amount of Fuel For A Single Ignition Event.
•  Start with Theoretical value of oxygen
•  Calculate Amount of fuel to add
•  Make corrections for:
      Physical Conditions (temperature, etc)
      Driving Conditions (acceleration, etc)
      Non Ideal Motor Performance
      Real Performance Tweak (Oxygen Sensor)

Inject the fuel.
•  Use Constant pressure system
•  Use a solenoid Valve (fuel injector)
•  Open the valve for various times to inject various amounts of fuel per ignition event

Components of EFI System.
•  Fuel Delivery
•  Pump, Regulator, Tubing, Injector(s)
•  Sensors
•  Temperature, MAP/MAF, Crank, Knock, TPS
•  Computer (ECU)
•  Software

Fuel Delivery Hardware.
•  Hi Pressure Pump (12 or 50 psi common)
•  Pressure Regulator
•  Return Line for regulator bypass flow
•  Pipes and Tubing
•  Injectors
      Lo P TBI
      Hi P Port style

About Injectors.
•  Location
   •  Outside Throttle Plate (TBI)
   •  Inside Manifold (Port)
•  Types
   •  Lo Pressure type (12 psi typical)
      •  Modest performance (but better than carb)
      •  Common in TBI applications
   •  Hi Pressure (43 psi or more)
      •  Great atomization great performance
      •  Usually used in port type applications

About Tubing, etc.
•  Steel tubing (mostly) 5/16 or 3/8
•  Small amounts of special EFI hose
•  Connection to Injector -Commercial or DIY-
•  Special Hose Clamps

About Sensors. •  Air Intake (MAP or MAF) (amount of oxygen)
•  Ignition Event (Crank, Distributor, Coil)
•  Temperatures (water, air, oil)
•  Throttle Position (TPS) detect accel, decel
•  Knock detect pinging

About the ECU (electronic control unit). •  Dedicated Small Computer
•  First were analog computers (Bosch)
•  All are now Digital devices
•  Can Do Extra Stuff
•  Retune car on the fly (self learn)
•  Control spark, fan, a/c, fuel pump, etc
•  Can be reprogrammed

EFI Summary.
•  EFI System has fluidic, mechanical and electronic components, all working together.

Retrofitting EFI.
•  Why bother?
•  Car runs much better
•  Engine lasts longer
•  More power
•  Much less pollution
•  Better gas mileage
•  Caveat: Safety in Working and Use

Retrofitting EFI Task.
•  Add
•  Sensors
•   ECU
•  Add and Locate Injectors
•  Fuel pump and tubing
•  Locate Injectors
•  Custom intake manifold for injectors (expensive)
•  TBI approach
•  Motorcycle TBI’s
•  Modify/Add to Stock Carbs
•  Modify Fuel System
•  Get Car to Run
•  Get Car to Run Right
•  Measure performance
•  Tuning Strategies

Retrofitting Approaches.
•  Replace With New Parts (manifold, etc) $$
•  Modify Existing System (IMHO preferred)

Add Sensors.
•  TPS - mounts on throttle shaft
•  MAP/ MAF - vacuum tube to manifold
•  Water T - into water line, on Radiator
•  Air T - air filter box
•  Ign Event - Crank, Distributor, or Coil(-)
•  Knock - Mount on Block

Add ECU.
•  Choose ECU (OEM or Aftermarket)
•  Choose Location
   •  Easy access for wiring, installation
   •  Protect from Water, Vibration, etc.
   •  Access to Firewall for Wiring to engine
•  Common Locations
   •  In Passenger Compartment
   •  Under Dash or on A Post panel

Selecting ECU.
•  Reprogram an OEM ECU
•  Complicated. but works
•  Use Aftermarket ECU
•  Several available, but most are expensive
•  Megasquirt is popular , much less expensive
•  Relatively inexpensive
•  Updatable via Internet
•  Very Flexible

Locating Injectors.
•  Before Throttle plate (TBI) simple, works well
   •  Modify Carb to hold injector (cheap) or
   •  Replace Carb with TBI unit
•  Into intake manifold (Port) more complications
•  Modify Manifold to hold injectors or
•  Replace manifold more expensive, but more likely to work right

About Locating Injectors.
•  In Front of Throttle Plate (TBI) simplest
   •  Modify Carb Body to hold Injector(s)
   •  Replace carb with a TBI unit (custom or from motorcycle, etc.)
•  In Intake Manifold
   •  Modify Intake (Not So Straightforward)
   •  Buy Intake and Throttle Body

Fuel Delivery System.
•  Choose EFI Pump
•  Choose Presure Regulator
•  Define Flow Path, Locate Components
•  Plumb up System
•  Set Up for Safety

Choosing Flow Path for Fuel.
•  Define location(s) of fuel pump(s)
•  Define location of Pressure Regulator
•  Define Regulator Bypass Flow Route
•  Define Final Flow Path
•  Check for Safety, Practicality