This presentation was prepared by Mechanical Engineers during their final year in their Internal Combustion Engine program offered at University of Engineering and Technology Lahore.

1. Types of fuel injection in SI and
CI engines, performance and
advantages over conventional
petrol engines
Presented by: Asad Saleem 2014-ME-302
Salman Imtiaz 2014-ME-303
Hannan Hameed 2014-ME-307
Farzad Qamar 2014-ME-336

2. Contents
• Introduction
• Types of fuel injection systems in SI engines
• Types of fuel injection systems in CI engines
• Advantages of modern Fuel injection methods in SI engines
• Advantages of modern Fuel injection methods in CI engines

3. Introduction
• All Internal combustion engines require injection of the fuel and air
into the combustion chamber to achieve combustion and
consequently produce power.
• Both SI and CI engines have different types of fuel injection systems
which will be described in detail.

4. Types of Fuel Injection in SI engines
1. Carburetion
2. Throttle body injection system
3. Multi point fuel injection

5. 1. Carburetion
• Formation of combustible air-fuel mixture outside the combustion
chamber by mixing proper amount of fuel and air is called carburetion
• This is done by a device called carburetor
• Appropriate for Petrol 4 and 2 strokes engines as petrol is more
volatile than diesel
• Fuel is atomized by relying on the air speed

6. 2. Throttle body injection system
• Similar to carburetor throttle body injection system with a throttle
valve controlling the amount of air entering the intake manifold
• Injector is placed slightly above the throttle body
• Injector sprays the gasoline into the air in the intake manifold where
gasoline mixes with the air and mixture passes through the throttle
valve and enters the intake manifold
• It may be timed or continuous type

7. 3. Multi point fuel injection
• Multipoint fuel injection (also called PFI, port fuel injection) injects
fuel into the intake ports just upstream of each cylinder's intake valve,
rather than at a central point within an intake manifold.
• 3 types:-
Sequential: Injection is timed to coincide with each cylinder's intake stroke
Batched: Fuel is injected to the cylinders in groups, without precise synchronization
to any particular cylinder's intake stroke
Simultaneous: Fuel is injected at the same time to all the cylinders

8. Types of Fuel Injection in CI engines
1. Mechanical injection system
2. Common rail injection system

9. 1. Mechanical injection system
• Fuel is forced into the cylinder by means of compressed air
• Not widely used anymore as it requires bulky multistage air
compressor which increases engine weight and reduces brake power
output
• Despite that it gives good mixing of fuel with the air resulting in a
higher mean effective pressure meaning higher indicated power for
the engine
• High viscosity fuels can be injected through this method

10. 2. Common rail injection system
• High pressure pump supplies fuel to a fuel header
• High pressure in header pushes to the respective nozzles located in
the cylinders
• At the proper time, a mechanically operated valve allows fuel to enter
the proper cylinder through the nozzle
• Length of push rod controls the amount of fuel entering in the
combustion chamber

11. Advantages of modern Fuel injection
methods in SI engines
• Uniform distribution in multi cylinder engines
• Higher volumetric efficiency
• Reduced or eliminated detonation
• Formation of ice on the throttle plate is eliminated
• Manifold wetting is eliminated
• Atomization of the fuel is independent of cranking speed and
therefore starting the engine will be easier

12. Advantages of modern Fuel injection
methods in CI engines
• Drastically cuts emissions
• Increased fuel efficiency
• Complete control over start and end of injection
• Injection pressure is independent of engine speed
• Variable injection pressure can be set