11/22/2016 1 11/22/2016 2 WHY GASOLINE INJECTION?

• To have uniform distribution of fuel in a multicylinder engine. • To improve volumetric efficiency. • To reduce or eliminate detonation.

11/22/2016 3 Electronic Fuel Injection (EFI) system main components

Modern gasoline injection systems use:

1. Solenoid Operated Fuel Injectors 2. An Electronic Control Unit (ECU) 3. Sensors

11/22/2016 4 1. Fuel Injectors

The fuel injector is a solenoid switch that’s either on (fuel flows) or off (fuel doesn’t flow). (Courtesy Kawasaki Motor Corp., U.S.A.)

11/22/2016 5 11/22/2016 6 Typical sensors for an electronic fuel injection system

• Exhaust gas or oxygen sensor - • Engine temperature sensor - • Air flow sensor - • Air-inlet temperature sensor - • Throttle position sensor - • Manifold pressure sensor - • Camshaft position sensor - • Knock sensor -

11/22/2016 7 Electronic fuel injection system

11/22/2016 8 Types of Injection Systems Injection Systems can be classified into: • Gasoline direct injection into the cylinder (GDI) • Port injection • Manifold injection

Another Classification of Injection Systems

 Multi-Point Injection (MPI) (a) Gasoline direct injection into the cylinder (GDI). (b) Port injection.  Single-Point Injection (SPI) (c) Throttle body injection

11/22/2016 9 a. Gasoline Direct Injection (GDI) Engine (Stratified- Charge Engines) • Fuel is injected directly into the cylinder during the intake stroke or the compression stroke • High pressure injector required, 5-10 MPa • Need bowl in piston design to direct the fuel spray towards the spark plug

11/22/2016 10 a. Gasoline Direct Injection (GDI) Engine (Stratified- Charge Engines)

During intake stroke air enters the cylinder

Near the end of the compression stroke fuel is injected and directed by the piston head bowl towards the spark plug

The mixture at the spark plug is “rich” in fuel thus easy to ignite but the amount of fuel injected results in an overall “lean” fuel-air mixture

Lowers heat transfer to the walls but increases thermal cyclic load on the spark plug, and standard catalytic converter doesn’t work

11/22/2016 11 a. Gasoline Direct Injection (GDI) Engine (Stratified- Charge Engines) Benefits of GDI system Engine that combines the best features of SI and CI engines:

• Operate at optimum compression ratio (12-15) for efficiency by injecting fuel directly into engine during compression (avoiding knock associated with SI engines with premixed charge)

• Control engine power by fuel added (no throttling  no pumping work)

• Increasing the engine volumetric efficiency.

• Create easily ignitable fuel-air mixture at the spark plug and a leaner fuel-air mixture in the rest of the cylinder.

• Lean burn results in lower emissions and higher energy efficiency

11/22/2016 12 a. Gasoline Direct Injection (GDI) Engine (Stratified- Charge Engines)

Benefits of GDI system • Manifold wetting is eliminated due to the fuel being injected' into or close to the cylinder and need not flow through the manifold.

• Formation of ice on the throttle plate is eliminated (Carburetor Icing).

11/22/2016 13 a. Gasoline Direct Injection (GDI) Engine (Stratified- Charge Engines)

Example:

Mitsubishi GDI engine achieves complete combustion with an air-fuel ratio of 40:1 compared to 15:1 for conventional engines

This results in a 20% improvement in overall fuel efficiency and CO2 production, and reduces NOx emissions by 95% with special catalyst

11/22/2016 14 b. Port Injection (Semi direct injection) Multi-point Fuel Injection (MPFI) system

11/22/2016 15 Multi point fuel injectors

11/22/2016 16 c. Single-Point Fuel Injection (SPFI) system Throttle Body Injection System

11/22/2016 17 Fuel Injection System

Air intake manifold

Throttle

Fuel tank 200 KPa

During start-up the components are cold so fuel evaporation is very slow, as a result additional fuel is added through a second injecting valve

11/22/2016 18 11/22/2016 19 11/22/2016 20 c. Throttle body for air flow control

11/22/2016 21 Problems associated with injection systems

• High maintenance cost, • Difficulty in servicing, • Possibility of malfunction of some sensors.

11/22/2016 22 11/22/2016 23 Injection in diesel engines

Diesel Indirect-Injection (IDI) Process Diesel Direct-Injection (DI) Process

11/22/2016 24