ENGINE AUXILIARY SYSTEMS

1. ENGINE AUXILIARY SYSTEMS
UNIT-II

2. • CARBURETORS:
• Carburetor is a device used for atomoizing and vapourizing
the fuel and mixing it with the air in varying proportions to
suit for changing the operating conditions of engines.
• Functions of carburetor:
 It prepares a mixture of petrol and air in correct
proportions.
 It maintains a small reserve of petrol in the float chamber
at constant head
 It atomizes and vaporizes the fuel.
 It supplies a fine spray of petrol
 It produces a homogeneous mixture
 It measures and supplies the proper quantity and
proportions of air and fuel under all conditions of engine
operation such as temperature, speed and load

3. Simple Carburetor

4. Multiple jet compensation

5. SOLEX CARBURETOR
TYPES OF CIRCUITS
1. Float circuit
2. Starting circuit
3. Idle and slow running circuit
4. Normal running circuit
5. Acceleration circuit

7. Starting circuit

9. ELECTRONIC FUEL INJECTION SYSTEM
FOR SI ENGINE

10. Limitation of carburetor
• In multi cylinder engines, it becomes very difficult for
simple carburetor to supply uniform quality and
quantity
• The induction passages are of unequal lengths
• Venturi throat of the carburetor causes a restriction in
the passage of air flow to the engine.
• Air-fuel mixture supply becomes acute at low speed
and air velocity decreases which causes less efficient
atomization
• There is a loss of volumetric efficiency
• Carburetor has many wearing parts. After wear, it
operates less efficiently

11. GASOLINE INJECTION SYSTEM
1. Multi-point injection system
2. Monopoint injection system

14. Electronically Controlled Gasoline
Injection System
• Fuel delivery system
• Air injection system
• Sensors and flow control system
• Electronic control unit

16. • Air sensor: How much of air being draw into the intake
manifold for adjusting the quantity of fuel
• Intake air temp sensor: measure the temp of the intake air
for fine tuning the mixture strength
• Exhaust gas oxygen: located in the exhaust system
provides ECU the amount of oxygen in exhaust gases. ECU
determine if the air/fuel ratio is correct.
• Manifold absolute pressure: It senses the vacuum pressure
in the engines inlet manifold & gives an indication of the
load to the engine.
• Speed/crankshaft: It provided the information to ECU
about engine rotating speed and the position of the
crankshaft.
• Engine temp: sense the temp of the coolant in the engine.
• Knock sensor: is a microphone type sensor that detects
the sounds of knocking so that ignition timing can be
retarded.

17. • Advantages:
• Very high quality fuel distribution is obtained
• Increase the volumetric efficiency
• No problem of air and fuel separation & design of manifold
becomes simple.
• Reduces the specific fuel consumption
• It is free from blowbacks
• Exhaust emission are less
• Better starting
• Disadvantages
• Initial cost high
• More completed mechanism
• Increased service problem
• More noise is generated
• Weight and space requirement are more than conventional
carburettor.

18. ELECTRONIC DIESEL INJECTION
SYSTEM
1. Unit injector system
2. Rotary Distributor system
3. Common rail direct injection system
4. (In this injection system such as timing, rate
of injection, end of injection, quantity of fuel
injected etc., is difficult if the engine is
operated at high speed). It may result the
reduced efficiency and higher emission
levels.

19. • Control of the parameters:
• Quantity of fuel injection, Injection timing, Rate of
injection during various stages of injection, Injection
pressure, speed of nozzle opening, pilot injection
timing and its quantity.
• Components of diesel injection system:
• Electronic sensors for registering operating
conditions and changes. A wide array of physical
inputs is converted into electrical outputs.
• Acuators or solenoids which convert the control units
electrical output signal into mechanical control
movement.
• ECU with microprocessors which process information
from various sensors in accordance with
programmed software and out put required
electrical signals into actuators and solenoids.

20. • Various sensors used in diesel injection system:
• Injection pump speed sensor
• Fuel rack position sensor
• Charge air pressure sensor
• Fuel pressure sensor
• Engine position sensor
• Temperature sensor
• Vehicle speed sensor
• Brake pedal sensor
• Clutch pedal sensor
• Accelerator pedal sensor
• Injector needle movement sensor

21. UNIT INJECTOR SYSTEM

22. • Four separate phases:
• 1. Filling phase
• 2. Spill phase
• 3. Injection phase
• 4. Pressure reduction phase
• Advantages:
• High performance for clean and powerful engines
• High engine power balanced against low
consumption and low engine emissions
• High degree of efficiency due to comppact design.
• Low noise level due to direct assemble in the
engine block.

23. Distributor system

24. • Advantages
• Simple construction
• Low initial cost
• Easy maintenance
• Balanced cylinder fueling
• Disadvantages:
• Overall reduced durability
• Practically suitable for small bore engines

25. Common rail direct injection system

26. • Good fuel efficiency and low CO2 emission
• System injects diesel five times more accurately than the
normal injection system by high response injects with
electronic control. The result is higher reduction in the Nox and
improving the fuel efficiency and increase the torque.
• Reduce the engine noise and vibration.
• High pressure fuel pump
• Common fuel rail
• Injectors
• Engine control unit
• Injection pressure does not depend on engine speed and loads.
• Control of injection parameters is easy.
• Pilot injection reduce the engine noise and Nox
• Fuel pressure is fed to both top and bottom of the needle
value.
• Fuel will flow through nozzle holes.

27. • Advantages:
• It delivers 25% more power and torque than the normal
direct injection.
• Initial cost is low
• Superior pick up is possible
• It maintain lower levels of noise and vibration
• Higher mileage is obtained
• Emissions are low
• Fuel consumption is less
• Improved performance is obtained.
• Disadvantages:
• Many parts involve the complicated design
• Production cost is high
• High degree of engine maintenance is required.

28. Battery ignition system

29. Magneto ignition system

30. ELECTRONIC IGNITION SYSTEM

31. Transistorised ignition system

32. Advantages
• Increase the life of contact breaker point
• It gives higher ignition voltage
• It gives longer duration of spark
• It has very accurate control of timing
• Less maintenance
• Disadvantages
• More mechanical points are needed similar to
conventional system
• It has a tendency to side tracking

33. Distributorless ignition system

34. Advantages
• No timing adjustments are required
• No distributor cap and rotor are required
• There are no moving parts to wear out
• Less maintenance is required
• It does not require a distributor to drive thus
providing less engine drag

35. CAPACITIVE DISCHARGE IGNITION
SYSTEM
• Used marine engines
• CDI module has capacitor storage of its own and sent a
short high voltage(about 250 + volts) pulse through the coil.
• The coil now acts similar to a transformers and multiplies
this voltage even higher.
• CDI module output is stepped up to 25,000V output form
the coil
• The advantages of CDI is the higher coil output and hotter
spark. The spark duration is much shorter(about 11-12
microseconds) and accurate.
• Better at high RPM but can be problem for both starting
and lean mixture or high compression situations
• CDI can use low resistance coils.

36. TURBO CHARGERS

37. • Purpose of turbocharger:
• To reduce the weight per horse power of the
engine as required in aero engine
• To reduce the space occupied by the engine as
required in marine engines.
• To have better turbulence and it ensured more
complete combustion giving greater power and
low specific fuel consumption
• To improve the volumetric efficiency
• To maintain the power of a reciprocating IC
engine even at high altitudes where less oxygen is
a available for combustion.

38. • Engine pollutants:
• Carbon monoxide(CO): air fuel mixture due to lack of
sufficient oxygen for the combustion of the fuel.
• CO has more affinity than oxygen for hemoglobin in our
blood. Affect the nervous system , finally affects heart.
• Carbon dioxide (CO2): During complete combustion the
hydrocarbons in the fuel are converted into carbon dioxide is
13.7% of exhaust gas.
• Nitrogen oxides(NOx):All combustion processes where air
containing nitrogen is burned. In high temp, nitrogen reacts
with oxygen produces nitric oxide (NO) and nitrogen
dioxide(NO2). Affect living organisms & blood purification
system.
• Hydrocarbons(HC): emissions are also the result of
inadequate amount of oxygen being present to support the
complete combustion of the air fuel mixture. This is
produces smog, affects vision of human being.

39. • Smoke: produced because of insufficient mixing
of fuel and air. It contains Co andCO2. When
cold starting, blue white smoke is produced
when more carbon particles are mixed with
exhaust. Irritation of eyes, coughing, headache
and vomiting.
• Sulphur oxide: is produced if the fuel has
sulphur. It may damage the plants. It causes
irritation to eye and throat and it gives
respiratory troubles to children.
• Lead: It is a toxic air pollutant. It affects liver and
kidneys. It causes mental effects to children.

40. • Pollution control:
• They formation of pollutants is prevented as far as
possible
• The pollutants are destroyed after they are formed.
• Hydrocarbon:
• Reducing the compression ratio
• Changing the design of combustion chamber
• Changing the design of piston
• By supplying lean mixture
• By maintaining of piston and piston ring.
• Methods of destroying of Hydrocarbon:
• By suppyling air to the inle manifold
• By using after burner
• By using catalytic converter

41. • Control of CO:
• By using closed loop control
• By supplying lean mixture
• By providing suitable overlap of valves
• Methods of destroying Co:
• By using reactor in the exhaust manifold
• By using after burner
• By using catalyst converter
• Control of oxides of nitrogen”
• BY supplying the exhaust again to the inlet manifold
• By spraying water in the inlet manifold to add moisture
to the mixture
• By using catalyst converter in the exhaust the oxides of
nitrogen can be destroyed

42. • Control of smoke and smog:
• Running the engine with a limited load
• Maintaining the engine well
• By adding barium salt in the fuel
• By using a catalyst muffler
• Methods of control:
• BY using catalyst muffler
• By changing the injection system in diesel engine

43. • Evaporative emission control for SI engine.
• Petrol vapour from fuel tank escapes into atmosphere by
evaporation
• When the engine is not running, petrol will evaporate in the
carburettor float chamber.
• Is consists of a device to store fuel vapour produced in the fuel
system due to evaporation
• Vapour liquid separater provided at the top of a fuel tank.
Vapour goes to the top of the separater where the liquid petrol
is separated and it is returned to the tank.
• A vent valve is provided for venteing the fuel vapour to the
canister.
• A canister containing activated charcoal is used to store the
fuel vapour. The canister adsorbs the vapour and store it.
• When engine running, the vacuum created in the intake
manifold is used to draw fuel vapour from the canister into the
engine.
• Purging air is sucked through the canister which leads the fuel
vapour from canister to the engine.

44. • Purging is the process by which the petrol vapour
is removed from the charcoal particles inside the
canister.
• Electronically controlled purge valve is used.
• During engine acceleration additional mixture
enrichment can be tolerated and under these
operating conditions the stored fuel vapour are
usually purged into the intake manifold.
• This system is a fully closed system.
• Flow of vapour from the fuel tank may be
controlled by a mechanically operated vent valve
or an electrically operated solenoid valve.

45. EXHAUST GAS RECIRCULATION SYSTEM

46. • Excessive nitrogen oxides(NO2) form when the peak combustion temp
exceeds 1950 C. to Lower the combustion temp, may engines have
EGR system
• Cooler exhaust gas absorbs heat from combustion process.
• It reduces the peak combustion temp and lowers the formation of
NO2.
• EGR system provides a passage between exhaust manifold and
inlet manifold.
• EGR control valve is used to regulate flow of EGR depending upon
engine operating conditions.
• The intake manifold pressure and exhaust manifold back pressure
may be used to control the EGR rate with vary with engine load.
• It consists of a spring loaded vacuum diaphragm linked to a tapered
valve.
• A vacuum chamber is provided at the top of the valve.
• This valve controls the passage of exhaust gas
• The chamber is connected by tube to a vacuum port in the throttle
body.

47. • When there is no vacuum at this port, the spring pushed
the diaphragm down and keeps the passage closed.
• No exhaust gas recirculated. It happens during idle when
NO2 formation is at a minimum.
• When the throttle is opened from the idle position,
vacuum applied will gradually open throttle valve.
• It causes the exhaust gas to flow into the intake
manifold. Open throttle, the intake manifold vacuum is
low and EGR valve is closed by the spring.
• EGR valve system do not affect full power operation.
• The exhaust gas is recirculated only in this system when
the engine operating conditions are supposed to form
NO2.

49. • 3way converters use two catalyst processes
• 1.Reduction and 2.oxidation processes
• Raduction catalytic converter is first stage and uses platinum and
rhodium to help in reducing Nox emissions.
• NO or NO2 molecule contacts the catalyst
• The catalyst rips the nitrogen atom out of the moleculle and holds
on to it, freeing the oxygen in the form of O2
• The nitrogen atoms bond with other nitrogen atoms which are also
stuck to the catalyst, forming N2.
• 2.oxidation catalyticis second stage of the catalytic converter.
• It reduces the unburned hydrocarbons and carbon monoxide by
burning them over a platinum nd palladium catalyst.
• This catalyst aids the reaction of the CO and hydrocarbons with the
remaining oxygen in the exhaust gas.
• The diesel engine catalytic converter is a pure oxidation catalytic
converter.
• It oxidizes HC and CO into water and CO2. It cannot reduce NO2.

50. • EMISSION NORMS (EURO AND BS):
• Reduction in emission:
• Vehicular technology
• Fuel quality
• Inspection & maintenance of in use vehicles
• Road and traffic management
• European countries the regulatory standards are
called the Euro Norms. Numerals I,II,III,IV in the
increasing order of strigency.
• The norms for vehicles vary from country to country
reflecting the differences in traffic density and
regulation, roe infrestructure, fuel quality,
maintenance standards.

51. • Euro norms refer to the emissons levels both
petrol and diesel vehicles.
• Union member countries, some automobile
manufacturing countries in Asia and Africa and
several non manufacturing countries.
• Euro-I – 1990, Euro –II – 1996, Euro-III -2000
• Euro-IV -2005, Euro-V standards for Cars-2009,
and new model cars -2011

52. • BS – Indian emission regulations was started in
1989. Then it is replaced by mass emission limit
both petrol in 1991 and diesel vehicles in 1992.