Electronic Fuel Injection• Prepared by:

SALMAN AHMED• Submitted to:

OMAIS ABDUR REHMAN

• Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive engines, having replaced carburetors during the 1980s and 1990s.

• The primary difference between carburetors and fuel injection is that fuel injection atomizes the fuel through a small nozzle under high pressure, while a carburetor relies on suction created by intake air accelerated through a Venturi tube to draw the fuel into the airstream

Carburettor• Carburettor is a device that

blends air and fuel for an internal combustion engine.• Air enters through the

throttle vale creating a lower pressure inside the venturi and this sucks in the fuel from the jet.

Problems with Carburettor.• A carburettor cannot give each cylinder precisely the same fuel/air mixture

because some of the cylinders are further away from the carburettor than others. • The twists and turns of the intake manifold can also cause the air and fuel

mixture to separate as it flows to the cylinders, resulting in uneven fuel mixtures between cylinders, making peak fuel economy, performance and emissions more difficult .• Incomplete combustion of fuel also results in toxic emissions like CO, NOx and

HC.• To meet this need Electronic Fuel Injection system are used nowadays in

automobiles.

To meet these problems Electronic Fuel Injection system was introduced.

• Electronic Fuel Injection system combines sophisticated computer controls with a high pressure fuel delivery system to provide optimum power and fuel efficiency.• The system is controlled by an

electronic control unit (ECU).

There are 3 types of Electronic Fuel Injection System

 in the market today.

1. Throttle body fuel injection2. Multipoint fuel injection3. Direct fuel injection

1. Throttle Body Injection • It consists of an electrically controlled fuel injector placed above the

throttle valve that sprays fuel into the throttle body.• Fuel pressure is created by an electric fuel pump and pressure is

controlled by a regulator.• Fuel is sprayed into the engine when the engine computer energizes

the injectors, which occurs in a rapid series of short bursts rather than a continuous stream.• It provides better atomization and does not have a troublesome

choke mechanism.

Throttle Body Fuel Injection System

2. Multipoint Fuel Injection System• Separate fuel injector for each cylinder.• Provides further precision by varying the fuel quantity and injection

timing by governing each injector separately. • Thereby improving the performance and controlling the emissions.• Since only air flows through the intake manifold, the intake manifold

remains dry and there are no problems with fuel puddling when the engine is cold or fuel separation causing uneven fuel mixtures in the center and end cylinders.

Multipoint Fuel Injection System

3. Direct Fuel Injection System• A separate injector used for each cylinder but the injectors are

relocated on the engine to spray fuel directly into the combustion chamber rather than the intake port.• Uses injectors that spray the fuel at a very high pressure(2200 psi)

directly into the combustion chamber.• The mixing of air & fuel occurs inside the combustion chamber rather

than in the inlet manifold.• Less fuel required to produce equivalent horsepower.• Significant improvement in fuel economy and power. (12%-25%)

Direct Fuel Injection System

Fuel Injector• A fuel injector is a spring-loaded solenoid

pintle valve.• When energized by the computer, the

solenoid pulls the valve open. allowing fuel to spray out of the nozzle and into the engine.• When the computer cuts the circuit that

powers the injector, the valve inside the injector snaps shut and fuel delivery stops.• Changing the pulse width, the volume of

the fuel to be delivered is varied.

Pulse Width

• The amount of fuel suppled to the engine is determined by the amount of time the fuel injector remains open. This is called pulse width and is controlled by the ECU.

Engine SensorsIn order to provide the engine with the correct amount of fuel for the operating conditions the engine control unit has to monitor a number of various sensors.

• Mass airflow sensor (Measures the amount of outside air entering the engine)

• Throttle position sensor (Variable resister connected to the throttle plate.)

• Coolant temperature sensor (Monitors the operating temperature of the engine)

• Manifold absolute pressure sensor (Measures the pressure, or vacuum inside the engine intake manifold.)

• Voltage sensor• Engine speed sensor

Comparison between Carburettors and Electronic Fuel Injection.

CARBURETTORS ELECTRONIC FUEL INJECTION

Winter drivability Poor Excellent

Summer drivability Excellent Excellent

Skill level required Average Advanced

Initial cost Low High

Long term cost High Low

Performance Good Better

Emission friendly Poor Excellent

Reliability Good Excellent

Fuel distribution Fair Excellent