EFI system

EFI system

1. Electronic Fuel Injection (EFI) SYSTEM SI ENGINE – EFI : TBI and MPFI BY S K Singh Centre for Energy Studies IIT Delhi

2. LIMITATIONS OF CARBURETTOR Non Uniform Mixture In Multi Cylinder Engines Accumulation Of Fuel In Manifolds So Uneven Mixture Distribution Rich Mixture Enters At End Cylinders And Leaner Mixture At Cylinders near To Carburettor !!!

3. NEED OF ELECTRONIC FUEL INJECTION (EFI)!! For uniform distribution of fuel in multi cylinder engines To Improve volumetric efficiency To prevent loss of fuel in scavenging in 2 stroke engines

4. Types of injection system (i) Gasoline Direct injection (GDI) (ii) Port Injection – Timed and continuous (iii) Manifold injection These three can be grouped under SINGLE POINT or MULTI POINT FUEL INJECTION (MPFI) SINGLE POINT (or Throttle Body Injection (TBI) ) : 1 or 2 injectors are mounted inside the throttle body MULTI POINT : 1 injector for each cylinder. Fuel is injected in more than one location

5. Types of injection system contd.. ( i ) Continuous injection : Uses a rotary pump (creates 0.75 to 1.5 bar pressure). Timing and duration of injection is determined by ECU Timed injection : A fuel supply pump supplies fuel at around 2 bar pressure when engine runs at maximum speed . Also fitted with an Injection pump and nozzle. Nozzle injection pressure: - At port 6.5 bar - Inside combustion chamber 16 to 35 bar

6. Basic components of injection system Pumping element Metering element Mixing element Metering control Mixture control Distributing element Timing control Ambient Control

7. Introduction to Electronic Petrol Throttle/Single Point Fuel Injection Systems The Carburettor has now been replaced with petrol injection systems. These systems supply the engine with a highly atomized mixture of air and fuel in the correct air/fuel ratio. This has the following advantages over the carburettor systems Lower exhaust emissions (pollution) Better fuel consumption Smoother engine operation and greater power Automatic adjustment of the air/fuel ratio to keep the vehicles Electronic Fuel Injector

8. Needle valve Electrical connector Fuel filter Fuel in Spring Armature Nozzle/jet Solenoid coil Electronic Fuel Injector Operation An injector sprays fuel into the inlet manifold by use of a solenoid coil. When the coil is switch on by the ECU, it pulls the armature/needle valve away from the nozzle, allowing pressurized fuel into the engine. When the coil is not switched on, the spring pushes the armature/needle against the nozzle, no fuel is injected into the inlet manifold Injectors are more precise and efficient than carburettors.

9. INJECTOR

10. Introduction to Electronic Fuel Injection (EFI) Systems Modern cars uses engine sensors, computer and solenoid operated fuel injectors to meter and inject the right quantity of fuel An Electronic control Unit (ECU) or the computer receives electrical signals in the form of current or voltage from various sensors. It then uses the stored data to operate the injectors, ignition system and other devices.

11. Introduction to Electronic Fuel Injection (EFI) Systems contd.. The ECU contains the following sensors: Exhaust gas or oxygen sensor (Senses O 2 in engine exhaust , calculates A/F ratio. Sensor output voltage changes in proportion to A/f ratio) Engine temperature sensor (senses coolant temp : increases richness if desired for cold starting) Air flow sensors (senses air and monitors quantity of fuel as per requirement) Air Inlet Temperature sensor Throttle position sensor (senses engine throttle position and adjusts mixture strength) (vi) Manifold pressure sensor (monitors vacuum in engine intake manifold so that mixture strength can be adjusted with changes in engine load) (vii) Camshaft position sensor (for speed and timing of injection) (viii) Knock sensor (microphone type – detects pinging noise or pre ignition noise so that the engine timing can be retarded)

12. The ECU (Brain) receives Information from various sensors. From this information it works out how much fuel the engine needs Inputs Outputs Single Point Injection Sensor

13. Advantages of Electronic Fuel Injection (EFI) Systems contd.. Increased volumetric efficiency No wetting of manifold Easy starting Better atomization, vaporization and mixing Less volatile fuel can be used A/F ratio variation negligible

14. Limitations of Electronic Fuel Injection (EFI) Systems contd.. High Initial cost High Maintenance cost Servicing problems Sensors problems

15. Electronic Fuel Injection Systems Two Basic arrangements are used Port Injection: injector is placed on side of the intake manifold near the intake port. The injector injects petrol into the air inside intake manifold. This mixture then passed through intake valve inside the cylinder for combustion. Every cylinder is fitted with separate injector 2. Throttle body injection (TBI) or Single point Injection: An injector is placed above the throat of the throttle body

16. Air drawn in by the engine Fuel Supply Throttle Body Throttle Valve Inlet Manifold The Engine Throttle Body/Single Point EFI

17. Single Point Electronic Fuel Injection (or Throttle body Injection TBI) System A fuel injector (may be 2) is located in a throttle body assembly that sits on top of the inlet manifold. Fuel is sprayed into the inlet manifold from above the throttle valve, mixing with incoming air. Fuel quantity, how much fuel is injected is controlled by an ECU. Single Point (Throttle Body) Fuel Injection ECU Fuel in Inlet manifold Air in TB injector

18. Throttle Body Injection contd.. The  throttle  body  injection  (TBI)  system uses one or two injector valves mounted in a throttle body assembly. The injectors spray fuel into the top of the throttle body air horn The TBI fuel spray mixes with the air flowing through the air horn. The mixture is then  pulled  into  the  engine  by  intake  manifold  vacuum. The throttle body injection assembly typically consists of the following: throttle body housing, fuel injectors, fuel pressure regulator, throttle positioner, throttle position sensor, and throttle plates. The THROTTLE  BODY  housing,  like  a carburetor body, bolts to the pad on the intake manifold. It houses the metal castings that hold the injectors, the fuel pressure regulator, and the throttle plates. The throttle plates are located in the lower section of the body. A linkage or cable connects the throttle plates with the accelerator pedal. An inlet fuel line and outlet return line connects to the fittings on the body.

19. THROTTLE BODY INJECTION SYSTEM CONTD.. A type of electronic fuel injection system that uses a single injector or pair of injectors mounted in a centrally located throttle body. The throttle unit resembles a carburetor except that there is no fuel bowl, float or metering jets. Fuel is sprayed directly into the throttle bore(s) by the injector(s).

20. EXAMPLE OF THROTTLE BODY INDIRECT MPI AND DIRECT MPI INJECTION SYSTEM

21. Multi-Point Fuel Injection MPFI SYSTEM Port Injection In this the injector is placed on the side of the intake manifold near the intake manifold

22. Air drawn in by the engine Fuel Injectors Throttle Valve Fuel Supply Inlet Manifold Injectors Engine Multi – Point S.I. Fuel Injection

23. M.P.F.I. System M.P.F.I. means Multi Point Fuel Injection system . In this system each cylinder has number of  injectors to supply/spray fuel in the cylinders as compared to one injector located centrally to supply/spray fuel in case of single point injection system . Multi-point fuel injection injects fuel into the intake port just upstream of the cylinder's intake valve, rather than at a central point within an intake manifold. MPFI (or just MPI) systems can be: SEQUENTIAL, in which injection is timed to coincide with each cylinder's intake stroke, BATCHED , in which fuel is injected to the cylinders in groups, without precise synchronization to any particular cylinder's intake stroke, or SIMULTANEOUS , in which fuel is injected at the same time to all the cylinders. Many modern EFI systems utilize sequential MPFI; however, it is beginning to be replaced by direct injection systems in newer gasoline engines.

24. More uniform A/F mixture will be supplied to each cylinder , hence the difference in power developed in each cylinder is minimum . Vibration from the engine equipped with this system is less , due to this the life of engine components is improved . No need to crank the engine twice or thrice in case of cold starting as happens in the carburetor system. 3. Immediate response , in case of sudden acceleration / deceleration. 4. Since the engine is controlled by ECM * (Engine Control Module), more accurate amount of A/F mixture will be supplied and as a result complete combustion will take place. This leads to effective utilization of fuel supplied and hence low emission level. The mileage of the vehicle will be improved. Advantage of M. P. F. I. System

25. CLASSIFICATION OF MPFI SYSTEM (i) D-MPFI SYSTEM & (ii) L-MPFI SYSTEM D MPFI SYSTEM: (Manifold Fuel injection system) Vacuum in intake manifold is first sensed and also senses volume of air by its density. As air enters into the intake manifold, the manifold pressure sensor detects intake manifold vacuum and sends information to ECU. Speed sensor - sends information about engine RPM to ECU ECU regulates the amount of fuel supply – injector sprays fuel in intake manifold

26. D-MPFI SYSTEM (Manifold FI system) Inlet manifold vacuum sensor Engine Air Mixture of Air and Fuel RPM Sensor ECU injector Injection into intake manifold Injection Volume control Fuel

27. CLASSIFICATION OF MPFI SYSTEM Contd.. L-MPFI SYSTEM ( Port Fuel injection system) The fuel metering is regulated by engine speed and amount of air that actually enters the engine. This is called air mass metering or air flow metering As air enetrs into intake manifold , the air flow sensor measures the amount of air and sends information to ECU. The speed sensor sends information about engine speed to ECU ECU processes received information and sends command to injector

28. Air flow sensor Engine Air Mixture of Air and Fuel RPM Sensor ECU injector Injection Near port Injection Volume control Fuel L-MPFI SYSTEM (Port FI system) Throttle valve