Types of air filter

The air filtration manufacturer has seen its share of changes over the last decade. They have created new products that not only have improved indoor air quality but also have reduced the cost of installation. When the American Society of Heating, Refrigeration, and Air-conditioning engineers introduced IAQ standards for an air filter. Among these several types of air filters are common in common HVAC systems. 

Different types of air filter: 

Fibreglass filter: This is the most common type of air filter. Layered fibreglass fibres are laid over each other to form the filter media and reinforced with metal supports to prevent failure. 

Polyester and pleated filter: This filter is similar to fibreglass filters but typically have a higher resistance to airflow and a superior dust stopping ability. 

Washable air filter: This filter is not common and relies on the build-up of dust along the clothes to improve the efficiency of a filter. 

High-efficiency particulate arrestance (HEPA) filter: Air passing through this filter at a very fine scale. The US department of energy (DOE) use this filter that meets standards. 

Carbon air filter: Carbon can be treated with oxygen, which opens the carbon's pores making it highly absorbent. It uses activated carbon to trap chemicals and gases, and can also filter cigarette smoke. These activated carbon air filters are well suited to an environment where chemical must be removed from the air. 

UV light air filter: This filter use reaction that occurs when titanium dioxide is exposed to UV light. As the air stream encounters the photochemical process, harmful particles, such as mould and bacteria, are neutralized. 


Explore more information : 

• Difference between the air filter and cabin filter

Positive caster Vs Negative caster

Positive caster is when the steering axis is in front of the verticle axis and negative caster is when the steering axis is behind the verticle axis. In this article, you have to clear your mind to check it out the difference between positive and negative caster, comparison and much more details about them.  

Difference : 

• Positive caster occurs when the axis of the steering wheel is ahead of the vertical axis and negative caster occurs when the axis of the steering wheel is behind the vertical axis.  
• A significant amount of positive caster provided that your vehicle has a well-fitted power steering system while negative caster symptoms make the steering wheel light and increasing the susceptibility of your vehicle, and make its path accurate without proper direction.
• Positive caster angles run between 3 - 5° on modern vehicles gives a good mix of highway stability and steering feel. Negative caster is opposite to positive caster. 

Summary : 

If you modify the caster settings on your vehicle, make sure that you keep the angular degrees of the casters completely symmetrical with one another. If you make the mistake of miscalculating the angles of the casters on various wheels of your vehicle, then you will find your car will start pulling more towards one side with respect to another side which doesn't have much of a caster angle. 

How to adjust correct steering angle?

The perfect steering is achieved when all the four wheels are rolling perfectly under all running condition. While taking turns, the perfect rolling condition is satisfied if the axis of the front wheels when produced meet the rear wheel axis at one point. Then this point is called the instantaneous centre of the vehicle. 

It can observe that the inside wheel is required to turn through a greater angle than the outer wheel. The larger the steering angle, the smaller the circle of turning. However, a maximum to which we can go as the steering angle. 

It has been found that steering angle can have a maximum value of about 44 degrees. 

The extreme positions are called lock positions on either side. The diameter of the smallest circle which the outer front wheel of the car can traverse and get when the wheels are at their extreme positions is referred to as the turning circle.

Now let we discuss the formula for correct steering angle. 

Correct Steering Angle

Let the axis of the inner wheels makes a larger angle θ than the angle φ subtended by the axis of an outer wheel. 

Let a = wheel track
b =  wheelbase
c = distance between the pivots A and B of the front axle

From the triangle IBP 

cotθ = BP / IP 

From the triangle IAP

cotø = AP / IP = AB + BP / IP = AB / IP + BP / IP = c / b + cotθ

cotø - cotθ = c / b 

This is the fundamental equation for correct steering. 

Explore more information: 

1. What is a caster?
2. Difference between the caster and camber

What is Toe in and Toe out | Definition | Effect

Definition : 

Toe-in is the amount by which the front wheels are mounted closer together on the front than on the back when the vehicle is stationary and viewed from the top. The wheel can be set closer to the rear than to the front, in which case the difference of the distances between the front and rear wheels is called toe-out. 

Effect : 

In rear-wheel-drive vehicles, there is usually an inherent tendency for the wheels to toe-out due to purposeful deviation from centre point steering due to errors in the steering angles of the inner and outer bends of the wheels. 

There is usually an inherent tendency for the wheels to toe-out in rear-wheel drive vehicles just because of purposeful deviation from centre point steering due to errors in steering angles of the inner and outer wheels bends. In order to compensate for this tendency, a small amount of toe-in was initially provided in such vehicles so that the wheels move perfectly straight ahead under normal turning condition. However, the initial toe-out was provided in the case of some front-wheel-drive vehicles to counter the toe-in present therein. 

In rear-wheel-drive vehicles, due to errors in the steering angles of the inner and outer bends of the wheels, there is usually an inherent tendency for the wheels to toe out. 

In rear-wheel-drive vehicles, there is usually an inherent tendency for the wheels to toe out due to purposeful deviation from centre point steering due to errors in the steering angles of the inner and outer bends of the wheels. A small amount of toe-in was initially provided in such vehicles to compensate for this tendency so that the wheels move perfectly straight ahead under the normal turning conditions. 

Toe-in generally does not exceed 3 mm. 

A toe-in wheel alignment can help to reduce oversteer problems and increase stability in front-wheel drives vehicles. 

A toe-out alignment can help to mitigate issues related to understeering and can improve the handling of a vehicle that has rear-wheel drive. 

Explore more information: 

1. What is a caster?

What is caster | Definition | Effect

Definition : 

The caster angle is called the angle between the kingpin centre line for the steering axis and the vertical in the wheel plane. 

If the centre line of the kingpin meets the ground at a point ahead of the verticle wheel centre line is called the positive caster and if it is behind the verticle wheel centre line is called the negative caster. 

Effect : 

The steering axis pulls the front tires, while the tire drag due to the weight of the vehicle is on the vertical line in the centre of the footprint. Since the positive caster steering axis would meet the ground ahead of the tire print centre, the later would always follow former, thus positive caster provides directional stability on the car wheels. 

A positive caster increases the effort required to turn the steering wheel. In the case of negative caster steering, it may be noted that it would be unstable. Example -There would be poor directional control, as in this case the centre of the tire print leads the steering axis. Extremely negative casters would cause shimmy and consequently cupped wear of the front tires. 

As the change of caster angle, the other angles of the steering geometry, the chamber, the inclination of the kingpin and the toe0in or toe-out are changed. Therefore, it is very important that this angle is adjusted first of all while doing the adjustment job. 

Approximately 3 degrees of castor gives good results. 

Explore more information:

1. Difference between caster and camber

Steering axis inclination | Definition | Purpose | Effect

Definition of Steering axis or Kingpin inclination : 

The inclination of the kingpin from vertical is called the king inclination or steering axis inclination. 

Steering axis inclination causes both front wheels to gain positive camber because they steer away from the centre.

In modern cars where the kingpin has been replaced by the ball joints, this term has also been termed as steering axis inclination. It is defined as the inclination of the ball joint axis from the steering vertical axis. The steering axis is an imaginary line drawn through the lower and the upper steering pivot pins. 

Steering axis inclination is set by the dimensions of the upright and therefore no adjustable once it defined. 

Purpose of steering axis inclination :

To determine vehicle stability while moving on the straight road. 

Effect of steering axis inclination :

Kingpin inclination also called steering axis inclination helps the straight-ahead recovery, thus providing directional stability. When the vehicle takes a turn, the inclination of the kingpin causes the vehicle body to move up in relation to the wheels. So when the steering wheel is left after the turn is completed, the weight of the vehicle tends to return the wheels to the straight-ahead position. 

Amount of inclination is about 7 to 8 degrees. However, the exact amount is decided considering the wheel rack value. It is kept below 8 since too much inclination cause a lot rising of the front axle when steering. 

Wheel alignment explained | Factors | Steering geometry | Linkage

What is wheel alignment?

Wheel alignment is the positioning of the steered wheels to achieve the directional stability during straight-ahead position, perfect rolling condition on steering and recovery after completing the turn. 

Factors of wheel alignment : 

Wheel alignment is used in connection with the stability and control of the vehicle while in the situation of motion. It means that while moving straight ahead the wheels should be parallel. In the event when they are pointing inward, they are said to toe in whereas if they are pointing outward they are said to toe out. Both these situations are undesirable because in either case while rolling forward, each wheel will be simultaneously slipping laterally due to which a continuous cross-tread scrubbing would take place. 

For good handling, steering, and vehicle stability, it is also necessary that 

• There should no be any setback, which is said to be the distance between the placing of the front tyres. In other word set back is a condition in which one wheel on an axle is in front of or behind the other wheel in relation to the chassis frame. When a set back of less than 6 mm is considered normal tolerance by some manufacturers. 
• The thrust angle should be zero. Thrust angle is the angle made by the thrust line with the longitudinal centre line of the vehicle. If the thrust angle is not zero, the vehicle will dog track the steering wheel will not be centred. When the thrust angle is zero, rear wheels follow the front wheels properly. Obviously, for this condition, all the four wheels should be parallel to the frame. This is called tracking. 

For effective steering under all conditions and at all loads, it is very important to consider and understand the factors which influence the stability and control of the vehicle. The factors are following below : 

• Factors pertaining to wheels 
• Steering geometry
• Steering linkage
• Suspension system 

Factors pertaining to wheels : 

• Balance of wheels 
• Inflation of tyres 
• Brake adjustment 

Steering geometry : 

• Camber 
• Caster 
• Toe-in 
• Toe-out

Steering linkage :

• Kingpin inclination ( Steering axis inclination )
• Combined angle and scrub radius 
• Over-steer 
• Under-steer 

Requirement of good steering system

For smooth and appropriate operation and performance of the steering system vehicle should fulfil the requirement given below : 

• The steering system should be very accurate and easy to handle. 
• The effort required to The spear should be minimal and must be not tiresome to the driver. 
• The steering the mechanism should also provide directional stability implies that the vehicle should have a tendency to return to its straight-ahead position after turning.
• To provide pure rolling motion to the wheel. 
• It should be designed in such a manner that shocks of the road are not transmitted to the driver. 

Principle of steering system

The steering system used along with suspension system allow driver to safely and easily control the direction of vehicle while driving. Now you can check the some functions of steering system. 

Primary function of steering system is to achieve accurate angular motion of the front wheels to negotiate a turn. This can be done through linkage and steering gear which convert the rotary motion of the steering wheel into angular motion of the front road wheels. 

Secondary function of steering system are following below : 

• To provide directional stability when the vehicle running on the straight road. 
• To provide perfect steering condition. For example perfect rolling motion of the road wheels at all times. 
• To provide facilitate straight ahead recovery after completing a turn. 
• To minimize tyre wear.

Disc brakes | Construction | Features

Construction : 

A disc brake can be made of a cast-iron disc bolted to the wheel hub and a stationary housing called calliper. The calliper is connected to some stationary part of the vehicle, like the axle casing or the stub axle and is cast in two parts, each part containing a piston. 

In between each disc and the piston, there is a friction pad held in position by retaining pins, spring plates etc. Passages are drilled for the fluid in the calliper to enter or leave each housing. These passages are also connected to another passage for bleeding. Each cylinder contains a rubber sealing ring between the cylinder and the piston. 

When the brakes are applied, hydraulically actuated pistons move the friction pads into contact with the disc, and later applying equal and opposite forces. On releasing the brakes, the rubber sealing rings act as return springs and retract the friction pad and pistons away from the disc. 

For this type of brake, 

T  = 2 µ p a R

Where, 

µ = fluid pressure 

a = cross-sectional area of one piston 

R = distance of the longitudinal axis from the wheel axis of the piston 

For special types of disc brakes include the swinging calliper type and the sliding calliper type. 

In-swinging calliper type the calliper is hinged about a fulcrum pin and one of the friction pads is fixed to the calliper. The fluid under pressure presses against the disc to the other pad to apply the brake. The reaction the calliper causes it to move the fixed pad inward slightly, applying equal pressure to the other side of the disc. The calliper automatically adjusts its position by swinging around the pin. 

In the sliding calliper type, there are two pistons between which the fluid under pressure is sent which presses on friction pad directly onto the disc, whereas the other pad is pressed indirectly via the calliper. Both these types are adjusting and have resulted in a simpler and lighter construction. 

Features : 

The discs of the brakes have made of pearlitic grey cast iron. The material is anti-wear properties. Cast steel discs have also been employed in certain cases, which are still less and provided a higher coefficient of friction, yet the big drawback in their case is the less frictional behaviour. 

Recently material like ceramics and carbon fibre have also found their way into automotive brakes. The greatest advantage of these materials is the weight reduction which greatly improves vehicle dynamics and steering characteristics, due to the reduction in unsprung mass. 

Two types of discs have been employed in various makes of disc brakes, for example, solid or the ventilated type. The ventilated type no doubt provides better cooling. It is seen that using a ventilated disc results in a reduction of about 30% in the pad temperature, as compared to solid discs. This results in a longer pad life. Whereas the ventilated discs also have certain disadvantages. They are usually thicker and even sometimes heavier than the solid discs. 

Some disc brakes use such friction pads as contain metallic contact inside. The contact is exposed when the pad wears down to the specified thickness and thereby completes an electrical circuit which lights up a warning lamp on the instrumental panel, indicating to the driver that the pads need replacement. 

Some large pistons for disc brakes are made of hard plastic whereas in some other cases, these are precision ground and plated with nickel-chrome which provides them with a hard surface which is durable. 

Drum brakes | Construction and Types | Factors

Construction and Types : 

In this types of brakes, a brake drum is attached concentrically to the axle hub whereas on the axle casing is mounted a backplate. In case of the front axle, the brakes plate is bolted to the steering knuckle. The backplate is made of pressed steel sheet and is ribbed to increase rigidity and to provide support for the expander, anchor and the brake shoes are protects the drum and shoe assembly from dust and mud. 

However, it absorbs the complete torque reaction of the shoe due to which reason it is sometimes also called a torque plate. Both brake shoes are anchored on the backplate. Friction linings are mounted on the brake shoes. Retractor springs are used to serve to keep the brake shoes away from the drum when the brakes are not applied. The brake shoes are anchored at one end whereas on the other hand force F is applied by means of some brake actuating mechanism. Which forces the brake shoe against the revolving drum, and hence applying the brakes. An adjuster is also provided to compensate for wear of friction lining with use. 

The relative braking torque obtained at the shoes for the same force applied at the pedal varies depending upon whether the expander is fixed to the brake plate or floating If the anchor is fixed or floating and then the shoes are leading or trailing. 

A

• Fixed expander type : 

To understand the action of this type it is necessary to understand the terms 'leading' and 'trailing' shoes. 

It is seen that a leading shoe tip is dragged along the drum even when there is no braking force, while the tip of the trailing shoe is thrown off the brake drum. Thus when the brakes are applied, the net force exerted on the leading shoe becomes more than the net force exerted on the trailing shoe and as such unequal braking effect is produced at the two shoes. With increased braking effect and consequently higher temperatures, the coefficient of friction gets reduced more with prolonged application in case of the leading shoe, due to which reason, leading shoe fades quicker than the trailing shoe. 

• Floating expander type :

In this type, the expander is not fixed on the backplate but is kept floating. In this way, the unequal braking effects at the two shoes are automatically balanced and made equal. Even if the lining on one shoe is worn more than on the other, the floating expander will move to one side so that the shoes still share equally the actuating force. However, the lining wear on two shoes is still unequal. 

• Floating anchor type :  

In this type of shoe operating mechanism, the two shoes are linked together at the floating anchor and have a common fixed anchor. For the direction of rotation, it is seen that both the shoes become leading, the details including merits and demerits of which are given below under separate bread since the shoes can be made leading by other means also. 

• Two leading shoe type : 

For this type, the leading shoe experiences an added breaking force or self energization. Thus if both the shoes are made leading, it definitely increases the braking torque. The lining wear also becomes uniform on both the shoes. However, the disadvantages are that firstly when the vehicle is moving in reverse, both the shoes will become trailing shoes and the braking effect is considerably decreased. This may not matter much because generally the vehicles in reverse are driven at comparatively slow speeds where the braking torque required is also less. Secondly, this type is sensitive to the coefficient of friction changes and thus will not be best suited for brakes meant for prolonged applications. 

• Two trailing shoe type :

In this type, both the shoes are trailing shoes as a result of which the braking effort at the wheels is decreased for the same force applied at the brake pedal as in case of two leading shoe type. That is why this type of brake is used generally with servo brakes or power brakes so that the driver is not fatigued. 
Apart from the above disadvantage of the decreased braking effort, this type has got a definite advantage. It has better anti-fade properties than the two leading shoe type and thus provides more consistent braking. 


Factors affecting braking effect : 

• The radius of the brake drum and the wheel 

Where Retarding force produced on a brake drum F = F_B * R_b / R_w

• The area of the brake lining and the amount of pressure applied at the brake lining increases the braking effect directly. 
• The higher coefficients of friction between braking surfaces and between tyre and road are also useful in increasing the braking effect, but two high coefficient may cause locking of wheels, which must be avoided. 

Types of brakes

There are different types of automotive brakes may be used according to the following considerations :

• Purpose
• Location 
• Construction 
• Method of actuation 
• Extra braking effort 

According to purpose : 

From this point of view, the brakes may be classified as the service or the primary and the parking or secondary brakes. The service brakes are the main brakes used for stopping the vehicle while vehicle in motion whereas the parking brakes are meant to hold the vehicle on the slop. 

According to the location : 

From this point of view, the brakes may be located either at the transmission or at the wheels. The wheel brakes are definitely better from dissipation point of view on account of two reasons. First, the location of transmission brakes from this viewpoint is very poor and secondary there is only one brake drum, whereas in the case of wheel brakes we may have four brake drums. Second, in case of transmission brakes, the whole of the braking torque has to be transmitted through the universal joints, propeller shaft, differential and the rear axle, suitable provision must be made in their design and their sizes increased proportionally.

However, if the brakes are located on the transmission, the braking torque is equally divided automatically between the two wheels and no special compensation is needed. Further because of the reduction at the differential, the transmission brakes would be stronger than the brakes of similar capacity at the wheels. 

Consideration the case of automobiles, the wheel brakes are used universally. 

According to construction : 

From this point of view brakes divided into two categories: One is drum brakes and another one is disc brakes. 

According to actuation : 

From this point of view brakes divided into following types : 

• Mechanical brakes 
• Hydraulic brakes 
• Electric brakes 
• Vacuum brakes 
• Air brakes 

According to the extra braking effort : 

When the weight of the vehicle is more that time driver can not apply the brakes comfortably without fatigue his effort is supplemented with some source of energy which makes the application of brakes easier. This types of brakes are called servo-brakes or power-assisted brakes. 

Brake efficiency and stopping distance

Braking efficiency : 

The maximum retarding force applied by the brake at the wheels F depends on the coefficient of friction between the road and the tyre surface µ. The weight of the vehicle on the wheel is W. 

F = µ F 

If the coefficient of friction achieved unity, the total retarding force produced at the wheels is equal to the vehicle weight itself, which is equal to the gravitational experienced by the falling body of the mass equal to that of the vehicle. 

If this is the case, the vehicle experiences a deceleration equal to the acceleration due to gravity g and the brakes are said to be 100 % efficient. Thus theoretical limit for brake efficiency is 100%.

In actual practice, the efficiency of 100% is rarely used for ordinary vehicles requirements like the safety of passengers in public vehicles. 

The brake efficiency usually varies from 50 to 80 % which enable the vehicle to stop within a reasonable distance. 

Stopping Distance : 

Approximate stopping distance at different vehicle velocities for various conditions of brakes are different. However, the minimum allowable limit of brake efficiency for any vehicle is 50 % for foot brakes and 30% for hand brakes. 

However, during emergency braking, the reaction of the driver and response time of the brakes also an important part. The stopping distance in case of emergency braking may be divided into 3 types : 

• Distance traversed during the reaction time of the driver. 
• Distance traversed during the time elapsed between the driver pressing the brake pedal and the brake being actually applied at the wheels. 
• Net stopping distance, depending upon the deceleration. 

Stopping distance mainly depends upon following factors :

• Vehicle speed
• Condition of tyre
• Condition of the road surface
• Coefficient of friction between tyre and road 
• Coefficient of friction between the brake drum and the brake lining 
• Braking force applied by the driver

Braking requirements

The braking system has a requirement for the correct breaking that will following below :

1. The brakes must be strong enough to stop the vehicle within a minimum distance in an emergency condition but this should also be consistent with safety. The driver must have proper control over the vehicle during emergency braking condition and the vehicle must not skid. 
2. The brakes must have good anti-fade characteristics like effectiveness should not decrease with the constant prolonged application and also descending hills. This requirement of the braking system demands the cooling of the brakes should be very efficient. 

Principle of braking system

The braking system is one of the most important control components of the vehicle. There are different types of brakes are used in various need. They are required to stop the vehicle within the smallest possible distance and this can be done by converting the kinetic energy of the vehicle into the heat energy which is dissipated into the atmosphere. 

Carter carburetor | Working

Carter carburettor is multiple jets, plain tube type of carburettor with only one adjustment which is for idling or low-speed operation.

Carter carburettor was established in 1909 and founded by William Carter, who started experimenting with automotive carburettors while running a bicycle shop.

Carter carburettor is normally used in Jeeps.

Working of carter carburettor:

A combination of fuel and air is drawn into the nozzle chamber through the jets on side of the nozzle forming a time spray which is carried by the standpipe to the venturi or main air passage, where it is absorbed by incoming air forming mixture on which engine operates.  

Jets on the side of the nozzle come into operation in direct proportion to throttle position. While more and the more throttle opened, the more jets are in operation. At wide-open throttle, all jets are working and the engine is getting maximum supply. 

Low-speed jet assembly supplies fuel to the engine at idle engine speed and up to approximately 20 km/h fuel flowing through a drilled passage connecting low-speed jet chamber with carburettor well. 

At idling, fuel is drawn through a low-speed jet and idling port at the edge of the throttle valve. With the idling screw, the mixture for idle running can be enriched or made leaner as required. 

What is magneto ignition system? | Construction | Working Principle | Advantages

Magneto is one of the special types of ignition systems with its own electric generator to provide the necessary energy for the system.

Construction of the magneto ignition system:

It is mounted on the engine and replaces all the components of the coil ignition system expect the spark plug.

When a magnet is rotated by the engine producing a very high voltage and it does not need a battery as a source of external energy. 

Magneto can be two types :

• Rotating armature type

In this type, the armature consisting of the primary and secondary windings all rotate between the poles of a stationary magnet.

• Rotating magnet type.  

In this type, the magnet revolves and the windings are kept stationary. 

Usually, the third type called polar induction type is also used. In this type, both the magnet and windings remain stationary but the voltage is generated by reversing the flux field with the help of soft iron polar projections is called inductors. 

Working principle of magneto ignition system:

At first, the magnets in flywheel rotate the magneto and magnetic flux of the magnets induces a current in the primary coil by the flywheel. 

A magnetic field develops around the primary coil with current flowing in the primary circuit. This magnetic field also surrounded by the secondary coil.  

The flywheel continues to rotate so the breaker points open and magnetic field produced by the current in the primary winding collapses. 

This collapsing magnetic field flows across the secondary coil which induces a current in the secondary coil. 

There is a winding ratio in the two coils that is 60:1 so the voltage is transformed to the 10000 and 15000 volts needed to fire the spark plug. 

Advantages of magneto ignition system:

• Reliable for medium and high speed. 
• Less maintenance.
• More effective because no battery is used. 

Disadvantages of magneto ignition system:

• Starting problem issue due to low cranking speed at a starting. 
• More expensive compared with the battery ignition system. 
• Possibility of misfire due to leakage because wiring carries very high voltage. 

What is engine cooling system

In the engine during the process of converting thermal energy into mechanical energy, the high temperatures are produced in the cylinders of the engine as a result of the combustion process. A large portion of the heat from the gases is transferred to the cylinder head and walls, piston and valves. These parts are damaged and the engine will also be damaged unless heat is carried away so the adequate cooling must be required. 

A cooling system must be provided not only to prevent damage to the vital parts of the engine, but the temperature of these components must be maintained within certain limits in order to obtain maximum performance from the engine. Hence, a cooling system is needed to keep the engine from not getting so hot as to cause problems and yet to permit it to run hot enough to ensure maximum efficiency of the engine. 

The function of the cooling system :

The cooling system keeps the engine from getting not too hot but at the same time not to keep it too cool either. 

Characteristics of an efficient cooling system :

• It should be capable of removing about 30% of the heat generated in the combustion chamber while maintaining the optimum temperature of the engine under all operating conditions of the engine. 
• It should remove heat at a faster rate when the engine is hot. 
• During the starting of the engine, the cooling should be minimum so that the working parts of the engine reach their operating temperatures in a short time. 

Types of the cooling system :

For cooling the engine a cooling medium is required. This can be either air or a liquid. 

According to that two types of the cooling system :

1. Liquid or Indirect cooling system 
2. Air or Direct cooling system 

In the liquid cooling system, there are five methods to cooled the engine. All five are listed below.

1. Direct or non-return system 
2. Thermosyphon system 
3. Forced circulating cooling system 
4. Evaporative cooling system 
5. Pressure cooling system 

In the air cooling system, there are two methods to cooled the engine. These are listed below.

1. Cooling fins 
2. Baffles 

Purpose of cooling system in engine

In the engine during the process of converting thermal energy into mechanical energy, the high temperatures are produced in the cylinders of the engine as a result of the combustion process. A large portion of the heat from the gases is transferred to the cylinder head and walls, piston and valves. These parts are damaged and the engine will also be damaged unless heat is carried away so the adequate cooling must be required. 

A cooling system must be provided not only to prevent damage to the vital parts of the engine, but the temperature of these components must be maintained within certain limits in order to obtain maximum performance from the engine. Hence, a cooling system is needed to keep the engine from not getting so hot as to cause problems and yet to permit it to run hot enough to ensure maximum efficiency of the engine. 

The function of the cooling system :

The cooling system keeps the engine from getting not too hot but at the same time not to keep it too cool either. 

What is capacitive discharge ignition system | Construction | Working | Advantages

The capacitor is used to store the ignition energy and the capacitance and the charging voltage of the capacitor determine the amount of stored energy. An induction coil is used to store the ignition energy in the battery ignition system. 

Construction of the CDI system:

The CDI trigger box includes the capacitor, thyristor power switch, charging device that is used to convert battery voltage to change the voltage of 300 to 500 V by pulse through a voltage transformer and pulse shaping unit and control unit.

Working of CDI system :

This system works by passing an electrical current over a capacitor. This type of ignition builds up a charge very quickly and starts by generating a charge and storing it up before sending it out to the spark plug in order to ignite the engine. 

The power passes through a capacitor and is transferred to an ignition coil that helps to boost the power by acting as a transformer and allowing the energy to pass through it instead of catching.

This system allows the engine to keep running as long as till charge is available in the power source.

Advantages of the CDI system:

• Insensitive to electrical shunts resulting from spark plug fouling.
• This system is suited to an application where insufficient dwell time is available because the capacitor can be fully charged in a very short time. 
• Short transient response.
• A fast voltage rise and shorter spark duration. 

Disadvantages of the CDI system: 

• The spark is strong but short in order to 0.1 to 0.3 ms which leads to ignition failure during lean mixture operating conditions because of fast capacitive discharge.
• This system generates a huge electro-magnetic noise so CDI is rarely used by automobile manufacturers.