MEC 306 AUTOMOBILE ENGINEERING

Unit I

Dr.T Ashok Kumar ME., Ph.D.,

SAP/SoME
SASTRA University

11-09-2021 1
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• UNIT I ENGINE AND AUXILIARY SYSTEMS 12 Hours
•
Introduction, Vehicle classifications; Engine components- details;
Performance Enhancement – turbocharger; Engine Auxiliary System:
Fuel supply system (SI engine) – SU electrical fuel feed pump,
carburetion - principle, Solex carburetor, gasoline injection (single
point, multipoint ); Fuel supply system (CI engine): fuel feed pump,
injection pump, injection nozzle, injection system - inline, distributor,
Common Rail Direct Injection (CRDI), Governor in diesel engine;
Lubrication System – pressurized lubrication system, lubricants
properties, oil cooler; Cooling System – types, pressurized cooling
system, coolants, antifreeze agent.
 MULTI - PORT FUEL INJECTION
SYSTEMS
A Typical Fuel Delivery System
 Drawbacks of a carburetor
• No Altitude compensation
• Mal-distribution of fuel
• Variation in air fuel ratio
• Inaccurate metering of fuel
• Does not meet emission
norms,
• Can not control Rise in Engine Idle RPM as engine
warms up.
• No temperature compensation
• No compensation for Exhaust gas Recirculation.
• No compensation for Positive Crankcase ventilation.
• No compensation for Canister Purge.
 Drawbacks of a carburettor
11. System supplies fuel a few revolutions of crank-shaft even
after the engine is switched off (Dieseling). Modified designs
require a separate anti-dieseling solenoid in the carburettor.
12. The carburettor gives correct air fuel mixture at only one
speed corresponding to the venturi design.
13. Fuel atomization depends upon the velocity of
air in the venturi.
14. Wall wetting effect occurs.
15. At high altitude, Carburettor Icing may occur at
the nozzle.
16. No compensation for the evaporative emission control
Petrol Injection is adopted for the following
reasons
•To have uniform distribution of fuel in a multi-cylinder
engine.
•To meet emission norms / standards
•To improve breathing capacity i.e. Volumetric efficiency
•To reduce Detonation
• To Improve Driveability for a l operating conditions.
•To provide system diagnosis when malfunction occurs.
•To Improve engine performance.
•To Reduce wastage of fuel during deceleration and over-
speeding of engine.
Petrol Injection is adopted for the following
reasons
•To Improve Driveability for a l operating
conditions.
•To provide system diagnosis when
malfunction occurs.
•To Improve engine performance.
•To Reduce wastage of fuel during
deceleration and over- speeding of engine.
•To Precisely time the injection of fuel.
•To Precisely meter the fuel.
•Adaptability to different operating
conditions.
Petrol Injection is adopted for the following
reasons
•To Precisely time the injection of fuel.
•To Precisely meter the fuel.
•Adaptability to dif erent operating conditions.
Methods of Petrol Injection
THROTTLE
BODY
INJECTION
THROTTLE
BODY
INJECTION
MULTI-POINT FUEL INJECTION
MULTI-POINT FUEL INJECTION
D-MPFI
System
•The D- MPFI system is the manifold fuel injection
system. In this type, the vacuum in the intake
manifold is first sensed.
•In addition, it senses the volume of air by its
density.
•As air enters into the intake manifold, the manifold
pressure sensor detects the intake manifold
vacuum and sends the information to the ECU.
•The ECU in turn sends commands to the injector to
regulate the amount of petrol supply for injection.
•When the injector sprays fuel in the intake manifold
the petrol mixes with the air and the mixture enters
the cylinder.
L- MPFI SYSTEM
•The L-MPFI system is a port fuel injection system.
• In this type, the fuel metering is regulated by the
engine speed and the amount of air that actually enters
the engine.
•The Air Flow Sensor measures the amount of air and
sends information to the ECU.
•speed sensor sends information about the speed of
the engine to the ECU
•ECU processes the information and sends commands to
the injector, in order to regulate the amount of petrol
supply for injection.
•When injection takes place, the petrol mixes with the air
and the mixture enters the cylinder.
 MPFI Electronic Control System

To Injectors
Sensors To Cold Start Injector (Input)
(Output)

Air Flow Ignition

Meter Signal

Cold Start Injector Electronic Control Unit (ECU)

Time Switch
 MPFI- Electronic Control
System
•The MPFI-electronic
control system is shown
in the form of block
diagram.
•The sensors that monitor
intake air temperature,
the oxygen, the water
temperature, the starter
signal and the throttle
position send signals to
the ECU.
MPFI- Electronic Control
System
•The air-flow sensor sends signals to the ECU regarding the
intake air volume.
•The ignition sensor sends information about the engine speed.
•ECU processes the signals and sends commands to the
injectors, to control the fuel injection.
Electronic Control Module(ECM) Control
functions
The ECU/ECM evaluates the sensor inputs using data
tables and calculations to determine the output of the actuating
devices.
. Injection volume control
•Injection timing control
•Ignition timing control
•Evaporative emission control
•Engine / vehicle speed control
•EGR control
 Electronic Control Module(ECM) Control
functions

• Injection volume control

1. Starting and Post start Enrichment
2. Warm- up Enrichment
3. Acceleration Enrichment
4. Full Throttle Enrichment
5. Overrun Fuel Cut-Off
6. Altitude Compensation
7. Closed- Loop Lambda Control
8. Idle Speed Control
9. Engine- Speed Limitations
10. Enrichment to avoid Detonation
MPFI- Fuel System
•In MPFI- fuel system, the fuel is supplied by the fuel pump. At the
time of starting, the cold start injector is operated by the cold start
injector time switch.
•The cold start injector injects fuel into the air intake chamber, thus
enriching the air-fuel mixture.
•The pressure regulator regulates the pressure of the fuel.
•The injectors receive signals from the ECU and inject the fuel
into the intake manifold.
MPFI- Air Induction System
•The MPFI- air induction system is shown in the block
diagram.
•The air cleaner, the air- flow meter, the throttle body and
the air valve supply a proper amount of air to the air
intake chamber and intake manifold
•The quantity of air supplied is just what is necessary for
complete combustion.
FUEL INJECTION CONTROL LAMBDA (λ) CLOSED LOOP
CONTROL:-
The λ sensor/ O2 sensor signal is processed by the ECU. The ECU
determines the required injector pulse width to maintain the air: fuel
ratio within the λ control window.
A sub-system of fuel control system is λ closed loop control.
Lambda λ is defined as the excess- air factor that indicates the
deviation of the actual air: fuel ratio from the theoretically required
ratio.

Quantity of Air supplied

λ= - - - - - - - - --
Theoretical required (14.7:1 for petrol)
LAMBDA (λ) CLOSED LOOP CONTROL: -

The λ sensor or exhaust gas O2 sensor is installed in the

exhaust upstream of the catalytic converter. The sensor
responds to O2 content of exhaust gas. The signal from λ
sensor serves as feedback to the fuel control system.
This provides control over air: fuel ratio to remain within
the limited catalytic converter window for optimum
catalyst performance.
The target is to stay close to λ = 1.
 Conversion efficiency of Catalytic
Converter as a Function of Excess
Air Factor
Catalytic Converter
Efficiency (%)

Excess Air Factor λ

LAMBDA (λ) CLOSED LOOP CONTROL: -

The system will operate in the closed-loop mode under

the following conditions:
•Coolant temperature above a specified value
•Timing out of the start- up delay timer in the logic module
•Generation of a valid oxygen sensor signal to the logic
module
•Operation of the vehicle under drive / idle or cruise
conditions.
FUEL INJECTION OPEN LOOP CONTROL:
-

The system will remain in open- loop mode under the

following conditions.

•Cold engine (until the oxygen sensor generates a signal)

•Park –neutral idle operation

•Wide – open throttle position

•Deceleration

•Absence of oxygen sensor signal for a specified period

of time
Idle speed control valve
An electric fuel pump & a pump-senderunit
A pressure-vacuum
gasoline filler cap.
This fuel injector design is equipped with a Pintle
type needle valve for precise fuel control
Top feed and bottom feed injectors
Grouped injectors in multiport injection
A typical Air-flow Sensor
A Mass Airflow Sensor
Knock Sensor
Mounted on Engine Block
Consists of Piezo-ceramic Measuring Element which
responds to noise oscillations
High Pressure Sensors for Petrol and Diesel
Systems
Senses absolute pressure of fuel in common rail.
Crank Angle Sensor
Mounted in close proximity of
flywheel
Senses engine speed
Air Temperature Sensor

Measures air
temperature in
manifold
Throttle Potentiometer Sensor

Mounted on
throttle valve
Inform ECM about
idle position,
deceleration, rate
of acceleration &
throttle open.
Oxygen (Lambda) sensor

Placed in
exhaust
manifold
It is ceramic device
that senses
contents of
exhaust gases
Advantages:
MPFI system provides
• Aaccuracy and adaptability in order to
minimize exhaust emissions and fuel
consumption
• Better driveability for all operating conditions
• Minimized evaporative emissions
• System diagnosis when malfunction occurs.
• Avoids detonation.
Advantages:

MPFI system provides

• Combustion of Homogeneous charge
• Higher power output than conventional engine
• Better Volumetric Efficiency
• Better Thermal Efficiency as higher
compression ratio can be employed
• Very lean mixtures with air: fuel ratio of 40:1
can be effectively used.
Disadvantages of MPFI system:
Systems are very costly.
Systems are too complicated.
Minor software glitches may cause
problems.
System failures can be repaired by
experts only, so maintenance cost is
high.
Gasoline Direct Injection System Layout
F uture trends:

• More and more dependence on

microprocessors to control the car
emissions.

• With simultaneous research in materials

technology, electronics and software the
future seems to be very bright for use of
GDI(Gasoline Direct Injection) Engine
Management systems.
 F uture trends:

•Gasoline (Petrol) engines have more

potential for Fuel Efficiency
improvements compared to the diesel
engines
•The gasoline engine has a 30 to 40%
potential for fuel economy
improvement over the standard
stoichiometric, 4-valve, PFI engine.
 Differences between PFI and TBI

PFI TBI
Fuel is injected into the port. Fuel is injected into the
center of the throttle body.

PFI uses top feed injector TBI uses bottom feed

injector
Fuel injector need not be Fuel injector needs to be
flushed flushed continuously- to
prevent formation of air
bubble.
Fuel injectors are equal to 1 or 2 Fuel injectors are
the number of cylinders used.
Differences between PFI and TBI

Port Fuel Injection Throttle Body Injection

PFI is comparatively high TBI is comparatively low

pressure injection pressure injection
(differential pressure = 2 to (differential pressure = 0.7
3.5 bar) to 1 bar )

Costly fuel pump is required Cheaper fuel pump is

to generate the required sufficient to generate the
pressure required low pressure.
Differences between PFI and TBI

Port Fuel Injection Throttle Body Injection

All cylinders receive equal Mixture mal-distribution

quantity and quality of air: may occur.
fuel mixture
More accurate fuel injection Less accurate fuel injection
control is obtained. control gives moderate fuel
Therefore increased fuel economy.
economy is obtained

Very low exhaust emission is Exhaust emission is above

achieved to meet the strict the permissible emission
emission norms. norms.
Differences between PFI and TBI
Port Fuel Injection Throttle Body Injection

Better throttle response as Moderate throttle response

fuel is injected on hot back as the fuel is injected at
side of intake valve and the throttle body and longer
shorter length of travel for length of travel for fuel to
fuel – to enter the engine enter the engine cylinder.
cylinder
This is costly system. This is a cheaper system.

Hither power output due Lower power output due

to low resistance at to lower volumetric
intake manifold and efficiency caused by
higher volumetric bulky injector body at
efficiency. the throttle body.
Engine Technology and Fuel Economy Improvement
Outlook

• As mentioned earlier, gasoline engines have more potential for

FE improvements compared to the diesel engines.
• The diesel engines have already achieved high levels of fuel
economy from going to direct injection (DI), adopting 4-valve
technology and turbochargers.
• It is estimated that the gasoline engine has a 30 to 40% potential
for fuel economy improvement over the standard stoichiometric,
4-valve, PFI engine.
• On the other hand, the fuel economy of HSDI engines can be
improved by 15 to 25% over that of the currently produced HSDI
car engines.
• The gasoline engines as discussed above would be using a
variety of technologies to improve fuel economy in the coming
years. GDI engines are likely to make more inroads in the
passenger car market.
Engine Types
The Indian passenger cars are largely powered by gasoline engines. During the
year 2007, the market share of gasoline passenger vehicles was 76%. All the
gasoline car engines are PFI engines with 3-way catalytic converters and presently
no GDI engine car is produced in the country.

The engine and vehicle technologies that can be adopted on Indian passenger
vehicles in a period of 2 to 3 years include;
variable valve timing and lift on gasoline engines,
HSDI in place of IDI diesel engine,
multi- valve diesel engines, turbocharging and CRDI fuel injection, idle
stop-start system (more likely in combination with integrated
starter/generator).

In the 4 to 5 years period the following technologies could be implemented;

GDI Engines,
integrated starter-generator,
CVT,
6- and 7- gear transmission on larger vehicles, and
HEVs in larger urban vehicle segment
MPFI Electronic Control
System
Thank You