Internal Combustion Engine

Prem Kumar
Assistant Professor
Department Of Mechanical Engineering
Government Engineering College Samastipur
 Module-V
❑ Ignition system:
❖ Battery and magneto ignition system,
❖ spark plug, firing order, quality, quantity & hit and miss governing.
❑ Lubrication system and Cooling system:
❖ Lubrication of engine components,
❖ Lubrication system – wet sump and dry sump,
❖ crankcase ventilation,
❖ Types of cooling systems – liquid and air cooled,
❖ comparison of liquid and air cooled systems.
 Ignition System
The ignition system is a system used to generate a very high voltage from the car battery and to
send it to each spark plug in turn thereby igniting the fuel-air mixture in the combustion chamber
of the engine.

Types of Ignition System:

❑Magneto ignition systems

❑Battery coil ignition systems

 Magneto ignition systems
❑This type of ignition system is mostly used in motorcycles, scooters and racing cars.
❑Working of the Magneto Ignition System:
• The engine's rotation drives the magneto, creating a magnetic field that induces a current in the
primary coil.
• As the breaker points open, the magnetic field collapses
rapidly, inducing a high voltage in the secondary coil.
• This high voltage is delivered to the spark plug,
where it jumps the gap, creating a spark to ignite the
air-fuel mixture in the engine.
❑The magneto Ignition system with main components is
shown in Figure
 Magneto ignition systems
1. Magneto
The magneto is the core component of the system that generates electricity. It consists of a
permanent magnet rotating around a coil or a coil rotating around a magnet.
Function:
• Converts mechanical energy into electrical energy.
• When the magnet rotates, it creates a magnetic field that induces current in the coil
(via electromagnetic induction).

2. Primary Coil
A low-resistance coil of wire (typically made of copper) within the magneto.
Function:
•It carries a low-voltage current induced by the magneto's movement.
•The primary coil is part
3. Secondary Coil
A high-resistance coil wound around or alongside the primary coil, but with more
turns of wire.
Function:
•Steps up the voltage generated in the primary coil to a high voltage
(thousands of volts).
•This high voltage is necessary to create a spark across the spark plug gap.
4. Breaker Points (Contact Points)
A mechanical switch that opens and closes the primary coil circuit.
Function: 3

• Interrupts the current flow in the primary coil, causing a sudden collapse of the magnetic field.
• This rapid change in the magnetic field induces a high voltage in the secondary coil.
2.
Magneto ignition systems
5. Cam
•A mechanical device used to control the timing of the breaker points'
opening and closing.
•Function:
• Synchronizes the breaker points' operation with the engine's
cycle.
• Ensures that the spark occurs at the correct point in the
compression stroke.
6. Distributor (Optional in Multi-Cylinder Engines)
•Used in multi-cylinder engines to route the high-voltage current to the
appropriate spark plug.
•Function:
• Directs the ignition spark to the correct cylinder in the correct
firing order.
7. Capacitor (Condenser)
•A small electronic component connected parallel to the breaker points.
•Function:
• Prevents arcing (sparking) across the breaker points when they
3
open.
• Ensures a rapid collapse of the magnetic field, maximizing the
voltage spike in the secondary coil.
2.
 Battery coil ignition Systems
❑ It is used in passenger cars and light trucks. A Battery Ignition system for four-cylinder engine
where the battery supplies the electrical energy.
❑ An ignition switch is used to control the battery current for starting or stopping the engine. The
ignition coil transforms the battery low tension current to high tension current required to
produce a spark by jumping in a spark plug.
❑ The distributor delivers the spark to the proper cylinder and incorporates the mechanical
breaker, which opens and closes the primary circuit at exact times.
 Battery coil ignition Systems
❑ The various units are connected by electrical wiring. The spark plugs
provide the spark in engine cylinder.
❑ The figure shows battery ignition system for a 4-cylinder petrol
engine.
❑ It mainly consists of a 6 or 12 volt battery, ammeter, ignition switch,
auto-transformer (step up transformer), contact breaker, capacitor,
distributor rotor, distributor contact points, spark plugs, etc.
❑ The ignition system is divided into 2-circuits namely the Primary
Circuit and Secondary Circuit.
❖ Primary Circuit : It consists of 6 or 12 V battery, ammeter,
ignition switch, primary winding it has 200-300 turns of 20 SWG
(Sharps Wire Gauge) gauge wire, contact breaker, capacitor.

❖ Secondary Circuit: It consists of secondary winding. Secondary

Ignition Systems winding consists of about 21000 turns of 40
gauge wire.
❖ Bottom end of which is connected to bottom end of primary and
top end of secondary winding is connected to centre of
distributor rotor. Distributor rotors rotate and make contacts with
contact points and are connected to spark plugs which are fitted
in cylinder heads.
 Working Principle
❑ When the ignition switch is closed and engine in cranked, as soon as
the contact breaker closes, a low voltage current will flow through the primary
winding.
❑ When the contact breaker opens the contact, the magnetic field begins to
collapse. Because of this collapsing magnetic field, current will be induced
in the secondary winding. And because of more turns of secondary,
the voltage goes upto 20000-35000 volts.
❑ This high voltage current is brought to centre of the distributor rotor.
❑ Distributor rotor rotates and supplies this high voltage current to proper stark plug depending
upon the engine firing order. When the high voltage current jumps the spark plug gap, it
produces the spark and the charge is ignited-combustion starts-products of combustion expand
and produce power.
❑ When compared to the magneto ignition system, the battery ignition system is more expensive
but at the same time it is very highly reliable as it aids in reliable sparking.
 Spark Plug
❑ The spark plug consists of a porcelain insulator in which there is an
insulated electrode supported by a metal shell with a grounded electrode.
They have a simple purpose of supplying a fixed gap in the cylinder
across which the high voltage surges from the coil must jump after
passing through the distributor.

❑ The spark plugs use ignition coil high voltage to ignite the fuel mixture.
Somewhere between 4,000 and 10,000 volts are required to make current
jump the gap at the plug electrodes.

❑ Spark plug gap is the distance between the center and side electrodes.
Normal gap specifications range between .030 to .060 inch. Smaller spark
plugs gaps are used on older vehicles equipped with contact point ignition
systems
 Firing Order
The order or sequence in which the firing takes place, in different cylinders of a multicylinder engine is called Firing
Order.
In case of SI engines the distributor connects the spark plugs of different cylinders according to Engine Firing Order.

❑ Advantages
(a) A proper firing order reduces engine vibrations
(b) Maintains engine balancing.
(c) Secures an even flow of power.
:
 Types Of Governing
1. Hit-and-Miss Governing
•Used in early stationary engines.
•Skips power strokes to maintain speed within a desired range.
2. Quality Governing
•Controls the quality (or air-fuel ratio) of the mixture supplied
to the engine.
•Common in diesel engines, where fuel quantity is adjusted
while maintaining constant air supply.
3. Quantity Governing
•Adjusts the quantity of the air-fuel mixture entering the engine.
•Common in carbureted petrol engines.
 Hit-and-Miss Governing
Hit-and-miss governing is a mechanical method of speed regulation primarily used in early single-cylinder engines. This
technique was designed to maintain a consistent operating speed despite fluctuating loads on the engine.
• The governing system operates based on the principle of selectively engaging or disengaging the engine’s power strokes to
maintain a target speed. This is achieved through a mechanical governor that monitors the rotational speed of the engine and
adjusts its operation accordingly.
1. Speed Monitoring:
1. A mechanical governor, often a flyweight or centrifugal type, is linked to the engine’s crankshaft.
2. The governor detects the rotational speed of the crankshaft and compares it to the pre-set desired speed.
2. Controlling the Power Strokes:
1. If the engine speed exceeds the desired range:
1. The governor actuates a mechanism that prevents either the ignition system from firing or the intake valve from
opening.
2. This results in a "miss," where the engine skips a power stroke, reducing its speed.
2. If the engine speed drops below the desired range:
1. The governor disengages the blocking mechanism, allowing normal operation of the ignition and fuel systems.
2. This results in a "hit," where the engine produces a power stroke, increasing its speed.
3. Cycle Continuation:
1. The hit-and-miss cycle continues dynamically, maintaining the engine’s speed within a narrow range under varying loads.
 Lubrication of Engine Component
Main component of IC engine to be lubricated
➢ Piston & cylinder
➢ Main crankshaft bearings
➢ Small and big end bearings of connection rod
➢ Cam, cam shaft and its bearing
➢ Valve and valve operating mechanism
➢ Timing gears
 Lubrication of engine component
The method of reducing the friction by introducing the substance called lubricant between the
mating parts is called lubrication.
Objectives
❑ Reduce friction thus increase efficiency
❑Reduce wear and tear of moving parts
❑Carry away heat
❑Provides sealing action between cylinder and piston rings, thereby it reduce blow by.
❑Provide protection against corrosion.
❑Lubrication film acts as cushion and reduce vibration
❑Carrying away the grit & other deposits and provide cleaning
❑Reduce noise
 Types of lubricants

❑Solid (e.g. Graphite molybdenum, Mica)

❑Semi-Solid (e.g. Heavy greases)

❑Liquid (e.g. Mineral oils, Vegetable Oils, Animal Oils)

 Type of lubrication system
Wet Sump lubrication system
➢ Bottom of the crankcase contain an oil pan.
➢ Oil pump supply the oil to engine parts.
Types :
➢ Splash Lubrication system
➢ Splash & Pressure feed system
➢ Fully Pressure feed system
Wet Sump Lubrication System-Splash Lubrication System
 Dry sump lubrication system
➢ Lubricating oil is maintained in a separate tank kept behind
the radiator.
➢ Oil is kept cool because of air blast thrown on the radiator.
➢ Due to less temperature, permits the use of thinner oil, which
reduces the friction.
 Oil Pump
Circulate the lubricant under pressure to various part of the engine.
Driven by gear mounted on the cam shaft.
➢ Gear type pump, which consist two meshing spur gears of
equal size in housing is commonly used.
➢ Pressure depends on speed
➢ Overcome excessive pressure, pressure relief valve is
provided, which bypass the oil into the pump inlet