GET TO KNOW YOUR CAR

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GET TO KNOW YOUR CAR.
A MUST DO COURSE FOR ALL DRIVERS 1. How You’re Engine Works.

V 1.0

1. a The engine is the entity which propels the car forward or backward. It is comprised of multiple parts which together develop horse power and in turn this is transferred to the crankshaft which is connected to the transmission and then to the back wheels via the differential and axle assembly. 1. b The first thing we are going to discuss is how the power is produced. There are a number of components that work together in the engine and they are: 1. pistons 2. connecting rods 3. crankshaft 4. inlet and exhaust valves 5. fuel injection or carburetor 6. sparkplugs 7. flywheel 1.c The first thing that occurs when you turn the ignition key is the starter motor engages the flywheel by means of a gear arrangement which in turn turns the crankshaft, attached to the crankshaft is the connecting rod and piston assembly. As the crankshaft turns, the piston moves down the cylinder bore creating a vacuum at the top of the piston (this is known as the intake stroke), this vacuum draws a mixture of fuel and air(in a fine mist) supplied by the carburetor(or in the case of a fuel injected engine it will be only air at this stage) past the inlet valve, until the piston is at the end of its stroke and the inlet valve is closed(at this point the fuel injection system will inject a fine mist of fuel into the cylinder). The crankshaft continues to turn and moves the piston in an upward direction, where the fuel/air mix starts to compress (compression stroke). When the piston is nearly at the top of its stroke the spark plug creates a spark and ignites the fuel/air mix, as the mixture burns the gas created expands at an enormous rate and as soon as the piston reaches the top of the compression stroke it is pushed back down with enormous force (power stroke), thus creating power output at the crankshaft. The crankshaft continues to move through the inertia created by the power stroke and with the aid of the flywheel which uses its weight to keep things moving, thus sending the piston back up the cylinder where this time the spent gases are pushed out the now open exhaust valve (exhaust stroke). The piston is again at the top of the cylinder ready to start the cycle again, but this time instead of the starter motor starting things off the stored energy through the inertia of the flywheel continues the cycle until the ignition is switched off. This process occurs alternately with each cylinder, not necessarily at the same time as each other, this will depend on the engines configuration. 1. d The valves are opened and closed by a camshaft, this turns in conjunction with the crankshaft and pushes the valves open at the appropriate time by the means of a push rod or directly by the “lobe” of the camshaft and a heavy duty spring fitted under the valve closes them when the camshaft rotates away from the valve.

2 1.e There are a number of different configurations that are used with engines such as V8, V6, inline 6 and inline 4 which are the more commonly used. The number refers to the number of cylinders and the “V” or “inline” refers to the configuration or shape of the engine. The different configurations are normally used depending on available area in the vehicles engine bay and power output required. V = cylinders set at an angle horizontally opposed. Inline = cylinders set one behind the other.

2. Engine Systems 2.1 Carburetor/Fuel Injection
2.1a. This is the means of metering the amount of fuel that is mixed with the air being drawn into the engine by the vacuum produced at the top of the piston as it moves down the cylinder on the intake stroke. 2.1b. Fuel is issued to the carburetor /fuel injection by means of a mechanical or electrical fuel pump. The pump will be mounted on the engine, in the case of a mechanical pump (driven by the engine) or on the body, particularly in the boot for electric fuel pumps. 2.1c. The amount of fuel/air mix will vary depending on the position of the accelerator as the more fuel/air mix is delivered to the engine the more power is produced.

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CARBURETTOR

2.2 Ignition System (Fig. 13)
2.2a. The spark that ignites the fuel/air mix is produced by the coil, this can be described as a type of transformer which transforms a low voltage i.e. 12 volts to something in the vicinity of around 18000 – 20000 volts which is needed for the spark to jump the gap between the centre electrode of the spark plug to the earth electrode. 2.2b. The coil is triggered by the opening and closing of a set of points or in the event of most modern cars an electronic switching system. 2.2c. The switching system is located in the distributor housing and is what causes the coil to produce a spark for every cylinder at the correct time. The distributor is known as such because it distributes the necessary high voltage to the correct cylinder when needed. 2.2d. Because there are different configurations for different engines, the order in which cylinder fires next will differ. All engines regardless of the amount of cylinders, will fire in a sequence that coincides with the compression stroke of a particular cylinder. Each cylinder fires in a predetermined order so the engine runs smoothly.

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2.3 Lubrication System (Fig. 14)
2.3a. The engine relies on good quality and the right amount of engine oil to perform reliably. 2.3b. If at any time the engine oil gets down below the add mark on the dipstick (the dipstick is fed into a small tube fixed to the engines sump to indicate the amount of oil in the engine) problems may occur. 2.3c. As the engine relies on adequate lubrication to enable all moving parts efficient operation, there is an oil pump fitted to all engines which has a pickup tube fitted to it to draw the oil from the bottom of the sump (an oil reservoir at the bottom of the engine) and distribute it under pressure to all internal moving parts. 2.4d. If at any time the pickup pipe doesn’t have any oil to pickup, oil pressure will be non existent and major damage can result (this will be prevalent with load noises coming from the engine). Oil pressure can also be very low or non existent if internal parts are worn excessively. Either of these two conditions will cause the oil warning light on the dash to come on not under any circumstance drive the car when this light is on pull over to the side of the road as soon as possible and turn the engine off. When the oil level is at a point that is dangerously low even turning corners, braking and accelerating, going up or down hills will uncover the oil pickup pipe, thus causing damage. Check your oil regularly. 2.5e. When topping up the engine oil always use the same oil that is in the engine already as there are many different oils available and they all use different specifications, mixing oils can destroy an engine. The best time and place to check your oil is before you first start it in the morning and on flat ground, giving all the oil in the engine a chance to run back into the sump. 2.6f. It is acceptable for an engine to use some oil (e.g. 1 litre per 1000 kms) as some will be burnt off in the cylinders as they are lubricated. If an engine is using too much oil it will be visible by seeing grey smoke coming from the exhaust pipe, normally as an engine becomes older it will start to use more oil. 2.6g. Oil loss may also be contributed by leaks from engine seals and gaskets; these will usually be evident by black oily deposits on the driveway. If an oil leak is left too long major problems may occur. 2.6h. Regular oil changes are necessary whether you use the car often or not as oil deteriates over time through the acids produced by the internal processes of the engine. Oil filters are fitted to all cars and these filter out the harmful waste products produced by combustion such as carbon deposits and fine metal particles in the oil. The oil filters should be changed at regular service intervals

2.4 Cooling System.
2.4a. When we top up the water or radiator we are topping up the cooling system. Part of the cooling system is an integral part of the engine block where waterways are cast into the block to remove heat from the cylinder head and the cylinders where the majority of heat is generated.

5 2.4b. The coolant is pumped around the cooling system by means of a water pump which is located on the engine in such a way that it is part of the waterway. The water pump is generally driven by a fan belt coming from the main engine pulley, and its primary job is to circulate coolant around the engine and through the radiator. 2.4c. The radiator is mounted in the front of the engine bay so as to make the most of the air flow that is created when the car is in motion. It is constructed of light weight aluminum alloy tubes and fins which dissipate heat very efficiently. The water enters at the top of the radiator and exits at the bottom back into the engine. As the water travels through the radiator it is cooled by the airflow created by the moving vehicle. It is also cooled by the fan blades when the vehicle is moving slowly or stationary. The radiator is connected to the engine by rubber hoses creating a sealed unit. 2.4d. The cooling system is pressurised not unlike a pressure cooker to allow a greater heat to be present before the coolant boils allowing higher operating temperatures. 2.4e. The cars heater is also ran of the cooling system and utilises both fan forced heating and flow through from the forward movement of the vehicle.

COOLING SYSTEM

3. Transmission (Fig. no. 1, 4, 8, 9, 10)
3.a. The transmission is connected to the rear of the engine by a torque converter in the case of an automatic transmission or a clutch assembly for a manual transmission. 3.b. The torque converter (fig.11) is driven by hydraulic fluid (automatic transmission fluid), one half is connected to the crankshaft and the other half connected to the transmission, each half having a series of small blades, the crankshaft side drives the transmission side by pressure created as the blades turn.

6 3.c. The clutch (fig.12) consists of a flywheel bolted to the crankshaft, a clutch plate and a pressure plate. The pressure plate in effect sandwiches the clutch plate, (which drives the transmission), between the flywheel and pressure plate thus transmitting power to the transmission. When the clutch pedal is depressed a series of levers release pressure at the pressure plate stopping power from being transmitted. 3.d. The transmission can be of manual or automatic configuration. It is used to convey drive to either the front or rear wheels or both depending on what is required. 3.e. In the case of a manual transmission the driver decides what gear to select whereas an automatic transmission more often than not decides on its own what gear to select depending on speed and load of the vehicle. 3.f. In the case of an automatic transmission there is a series of clutch and band mechanisms which are used to control encased gear sets and are energized by hydraulic fluid pressure; these are controlled by a central hydraulic switching unit known as the valve body. This unit controls how many and which band or clutch pack is utilised to produce the required gear. 3.g. When the gear stick is used to select a specific gear the flow of fluid is transferred directly to the corresponding unit to provide the chosen gear. In the case of the transmission changing gears on its own, this is regulated by hydraulic valves inside the transmission that are sensitive to the throttle position and the road speed of the vehicle, these in turn cause the pressure at the valve body to change, altering the flow of fluid and the appropriate gear is chosen. 3.h. There are various configurations to automatic transmissions i.e. 3 speed, 4 speed, some are controlled by the use of control rods and others by electronic means. Most late model cars utilise the cars computer to sense all aspects of the engine and transmission to select the appropriate gear so as to obtain the best fuel economy and drivability. 3.i. The manual gearbox is as the name suggests all gear selections are done manually by the driver. When a gear is selected, instead of hydraulic pressure being used to select that gear a series of selector rods move the corresponding gears into place. 3.j. These gears are sized to correspond to the gear we select. For instance, when 1st gear is selected a small gear will drive a larger gear, allowing the engine to develop power at a slow speed thus enabling the vehicle to go up steep grades. Therefore as a higher gear is selected so the speed of the vehicle increases.

AUTOMATIC TRANSMISSION

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4. Final Drive (Fig. no. 1, 2, 10)
4.a. Connected to the transmission is the final drive, this is connected via a tailshaft for rear wheel drive vehicles and generally through a set of gears for front wheel drive vehicles, this unit drives the road wheels. 4.b. In the case of a front wheel drive vehicle, the engine, transmission and final drive are situated under the bonnet in a compact unit, opposed to a rear wheel drive vehicle where the engine, transmission and final drive are spread throughout the length of the vehicle. 4.c. The final drive unit comprises: 1. housing 2. crown wheel and pinion 3. differential assembly 4. axles 5. hubs which the wheels bolt to. 4.d. The crown wheel and pinion are positioned in the final drive housing. Both the crown wheel and pinion are gears, where the pinion gear is driven by the output of the transmission and the crown wheel is driven by the pinion gear. The pinion turns approximately 3 to 4 times to one turn of the crown wheel, allowing the engine to produce sufficient power to move the vehicle, similar to the gearbox. 4.e. The differential is fitted to the crown wheel and transfers power at right angles to the axles. The differential also comprises a gear system which enables the axles to turn at different speeds when cornering to allow the vehicle to corner smoothly otherwise the vehicle tends to be pushed straight ahead. PINION GEAR HOUSING

CROWN WHEEL WHEELWHEEL

DIFFERENTIAL AXLE

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5. Brakes (Fig. no. 1, 3, 10)
5.1 Brake Master Cylinder and Booster 5.1.a. All vehicles of today employ the use of a brake booster, this is used in conjunction with the brake master cylinder. The brake booster greatly enhances the pressure needed at the brake pedal. The brake booster uses vacuum created at the engines inlet manifold for its power. Inside the brake booster there is a rubber diaphragm which is sealed to the inner edge of the booster housing, in the centre of the diaphragm is a push rod which is the brake master cylinder actuating rod. The rod is connected to the brake pedal arm and when the brake pedal is pushed, the vacuum which is present at the engine side of the diaphragm helps the master cylinder actuating rod apply brake pressure to the braking system. 5.2 There are two major types of braking systems these being drum and disc brakes. 5.3 Drum brakes 5.3.a. The main components of a drum brake system are: 1. backing plate 2. brake shoes 3. wheel cylinders 4. brake drum 5.3.b. The brake backing plates are bolted to the final drive housing or front hub assembly. The brake shoes are fastened to the backing plate usually by a retaining spring or clip which allows them to move a small amount. One end of the shoe sits on a fixed bracket where it is allowed to pivot slightly and the other end sits on the wheel cylinder. When the brake pedal is applied, brake fluid is forced into the wheel cylinder, (issued by the brake master cylinder via small steel and rubber hoses) and as fluid doesn’t compress it forces the pistons in the wheel cylinder outward moving the brake shoes out onto the brake drum thus slowing down the vehicle. The brake shoes have a layer of braking material fixed to them, this material allows the braking effect to be smooth and is designed to take a great deal of heat that of which is generated by the braking procedure. 5.4. Disc Brakes 5.4.a. The main components of a disc brake system are: 1. disc caliper 2. disc pads 3. disc 5.4.b. The disc caliper is mounted in such a way that it stays in line with the disc at all times and is comprised of two pistons which fit over the disc. Positioned at each of the pistons are the brake pads, these also have a layer of braking material. When the brake pedal is applied the pistons move outwards onto the disc, basically trapping the disc in between the brake pads and effectively stopping the vehicle.

9 5.5. Application 5.5.a. Different manufacturers use different brake setups, where a majority use disc brakes at the front of the vehicle as a majority of the braking is done by the front brakes and drum brakes at the rear for small and family cars, but chose to fit disc brakes at all four wheels for the more sportier models. 5.5.b. There are advantages and disadvantages for both brake systems. Drum brakes are generally more efficient as there is more surface area, but generate a lot of heat which will reduce the braking performance. Disc brakes on the other hand have less surface area and require more pressure to work effectively, but dissipate heat very efficiently and therefore are more beneficial if the vehicle is doing a lot of braking at higher than average speeds. 5.6 Handbrake 5.6.a. The handbrake is controlled by the use of a wire cable which is attached at one end to a handbrake lever in the vehicle located at a point which is easy for the driver to access and the other end attached to the braking system at the rear wheels. 5.6.a. When the handbrake is applied it manually actuates the rear brake assembly applying the brakes. The actuating lever in the vehicle is held in position by the means of a ratchet system which stops the handle from going back to the off position. When the driver decides to release the handbrake the ratchet mechanism is released and the lever is returned to the off position.

BRAKING SYSTEM

DRUM BRAKES

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6. Suspension (Fig. no. 1, 2, 3, 10)
6.1 There are various types of suspension used in vehicles today e.g. • Coil spring • Leaf spring • Torsion bar • Pneumatic • Hydraulic Which ever system is used they all work on the same principal and that is to suspend the body of the vehicle from the wheels and axles to give a comfortable ride and good handling characteristics. 6.1.a. If a suspension is soft it will be comfortable, but when cornering at any sort of speed it will tend to be harder to handle as the suspension will allow the body of the vehicle to move or roll around slightly, therefore the weight of the vehicle through inertia will unbalance the vehicle and it will be harder to control. Whereas a vehicle with hard suspension will have a very harsh ride, but will handle or corner very well as the body won’t move around as much allowing more stable handling. 6.2 Shock absorbers 6.2.a. Shock absorbers are an oil filled hydraulic dampening device which are used in conjunction with the suspension. They are fitted in between the body and the axle assembly and are used to slow down the rate of rebound that a spring produces. Without shock absorbers a sprung suspension will continue to bounce due to the energy created when a spring is compressed then released. The dampening effect of a shock absorber is controlled by internal valves, these can be of varying sizes depending on the use of the vehicle i.e. sports cars will have more dampening to allow the suspension to move less when cornering and a family car will have less dampening to allow a smoother ride.

COIL SPRING SUSPENSION

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7. Steering (Fig. no. 1, 6)
7.1 The steering system consists of these main components: 1. 2. 3. 4. steering Wheel steering column steering box or rack steering arms

7.1.a. We use the steering wheel to provide leverage to the steering components, that is why the steering wheel is proportional to the vehicle we are driving i.e. if we used a trucks steering wheel in a car it would be very easy to turn because of the leverage effect, but it would take forever to turn because of its size. 7.1.b. The steering wheel turns the steering column which is connected to the steering box or rack. These assemblies are the two methods of directing the movement of the steering wheel to the steering arms which are connected to the front hub assemblies. The hubs are mounted on the suspension in such a way that they are able to pivot left to right freely when the steering arms move, the road wheels are mounted on the hubs therefore the wheels turn in the direction that the steering wheel is directed. 7.1.c. All steering systems have some sort of adjustment to allow for wear in the suspension components and the steering components. This adjustment is referred to as wheel alignment. It is imperative that the steering is kept within manufactures specifications and by making these small adjustments the tires will have maximum life and the vehicle will be safe to drive. 7.2 Power Steering 7.2.a. Power steering is provided to take the physical effort from steering the vehicle and make steering less of a chore. Power steering uses hydraulic power provide by a hydraulic pump mounted on the engine and generally driven by a belt from the engines main crankshaft pulley. Hydraulic pressure is fed to the steering box or rack by high pressure hoses which helps the components move when needed.

STEERING RACK

STEERING BOX

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RACK AND PINION STEERING

8. Charging System
8.1.a As we are well aware the battery stores power to allow us to start the car and run any electrical device on the vehicle, but as all batteries it will eventually run out of power. Therefore there is an inbuilt charging system on all motor vehicles. 8.1.b. The main unit used to do this is the alternator or on older vehicles the generator. This unit produces electrical power by the means of a stator which spins inside a series of windings housed in the alternator housing. 8.1.c. Most vehicles use a 12 volt system and the amount of amps(power) produced will vary accordingly to the amount of windings in the alternator, this will be relevant to the vehicles usage, basically the more electrical systems fitted to the vehicle such as lights and management computers the more amps will be needed. 8.1.d. The battery can only store a predetermined amount of power; therefore the alternator will provide any extra that is required. As some systems (i.e. engine management computer) depend on the alternator as their main power source the alternator needs to be able to supply the correct amperage otherwise problems may occur. 8.1.e. The batteries stored power is replenished by the alternator/generator and that is controlled by the regulator. The regulator will only allow the battery to be charged to its maximum capacity as it senses the current flow and reduces the charge rate accordingly. 8.1.f. Due to the constant charging effect that the battery undergoes it will heat up slightly, therefore the water/acid solution that is in the battery will eventually evaporate, that is why the battery water level should be periodically checked so that there is sufficient water in the battery. This is normally carried out when the car is serviced using distilled or previously boiled water.

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CHARGING SYSTEM

9. Exhaust System (Fig. no. 6)
9.1.a. The exhaust system carries burnt combustion gases from the engine to the outside of the vehicle. This is done by the exhaust pipe which incorporates one or more mufflers. The muffler restricts the amount of exhaust noise created by the engine and can influence the performance of the vehicle depending on its construction. 9.1.b. While the mufflers job is primarily to reduce noise, if it is too restrictive it can reduce the flow of exhaust gases exiting the engine consequently reducing the amount of fuel/air mix from entering the engine, subsequently reducing engine performance. This can sometimes happen if an internal part of the muffler has broken off and interrupts the flow of exhaust gases, also if the incorrect muffler has been fitted this could effectively reduce the flow of exhaust gases. 9.1.c. After market exhaust systems are available that can improve the engines performance and fuel economy, but this will normally be at the expense of creating more exhaust noise.

EXHAUST SYSTEM

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10. Wheels and Tyres
10.1. Wheels 10.1.a. Wheels are constructed of either steel or aluminum alloy and can vary in width and diameter. When larger diameter wheels are used special tyres have to be fitted. There are advantages in using larger diameter wheels such as more precise cornering, but this at the sacrifice of ride comfort as the tires used on these rims have less of a cushioning effect. 10.2. Tyres 10.2.a. Tyres are made of rubber and steel belts. The steel belts are constructed of woven steel wire which is encased in rubber; this gives them both strength and grip. There is a great deal of different types of tyres to choose from, some offer greater grip often at the sacrifice of ride and life span, where others offer better ride and longer life.

11. Vehicle Maintenance
11.1.a. All vehicles have a routine maintenance schedule which is provided by the manufacturer at time of sale and should be adhered to from when the vehicle is new. 11.1.b. A well maintained vehicle will give relatively trouble free motoring. The schedule takes into account the life expectancy of things such as oil life, oil filtering capabilities, air cleaner life and numerous checks and adjustments throughout the vehicle, when carried out at the correct intervals will give optimum vehicle life. 11.1.c. Lubrication of all moving parts and components such as wheel bearings, suspension components down to door striker plates and hinges will reduce the amount of wear and consequently give optimum life to these components. 11.1.d. Daily checks can be carried out by the owner such as oil level, water level and all lights including indicators and brake lights, ensuring safe motoring.

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