Unit 1

VEHICLE STRUCTURE AND ENGINES

ENGINE:

Engine block assembly

⦁ Very sophisticated casting.

⦁ Made of cast iron or aluminum with cast iron cylinder liners.

⦁ A great deal of machining involved in the process of manufacturing.

⦁ Becomes the frame of the engine.

Bottom end parts:

⦁ Block

⦁ Crankshaft

⦁ Connecting Rod

⦁ Pistons, Rings, & Wrist Pin

⦁ Bearings (Main and Connecting rod)

⦁ Caps (main and Connecting Rod)

⦁ Fly Wheel and nuts and bolts

Cylinder block configurations:

⦁ Common cylinder configurations:

⦁ Vee, inline, opposed

⦁ And slant.

⦁ Number from farthest front backwards

Crankshaft:

⦁ Converts reciprocating motion into rotary motion.

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⦁ Made of either nodular iron, forged steel, or billet steel

Crankshaft bearings:

⦁ Known as friction or precision insert bearings.

⦁ Uses a steel backing with soft metal on crankshaft side.(lead, tin, copper, silver,

cadmium)

⦁ Oil clearance between crankpin and bearing very critical. (.001”)

⦁ Oil Clearance measured with plastigauge.

⦁ The flywheel (known as the flex plate when used with an automatic transmission)

carries the engines inertia in between power strokes.

⦁ It is the powers take off for the engine. The clutch or torque converter bolts to it.

Lastly it has the starter motor’s ring gear

Vibration damper:

⦁ The vibration damper smoothes the vibrations caused by the power strokes.

⦁ It has a pulley on it the run auxiliary systems.

⦁ It may contain timing marks or crankshaft timing sensors.

Balancer shafts:

⦁ Used to counteract the normal vibrations inherent to piston engines.

⦁ Found on 4 cylinder and 6 cylinder engines mostly.

Cover and pans:

⦁ Made of steel metal, aluminum, or plastic materials.

⦁ Usually use gaskets or seals

Gaskets seals and sealers:

⦁ Gaskets seal two stationary surfaces.

⦁ Seals do it when one surface moves.

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⦁ Many types of materials: rubber, paper, aluminum, steel, cork and more.

⦁ Sealers adhere gaskets to one of the surfaces.

Pistons:

Pistons harness the energy of the power stroke and transfer the force toward the crankshaft.

⦁ Head or crown

⦁ Ring grooves

⦁ Ring lands

⦁ Oil return holes

⦁ Skirt

⦁ Pin hole

⦁ Pin boss

⦁ Pin offset

Piston rings:

⦁ Rings seal the compression in the combustion chamber and the motor oil in the

crankcase.

⦁ Automotive engines use 3 rings: 2 compression and 1 multi-piece oil ring

Types:

⦁ Rings are usually made of cast iron

⦁ can be plated with chrome or molybdenum.

⦁ Help seal the ring to the cylinder wall.

⦁ Shapes of the ring vary to also help the ring seal better.

Piston pin:

⦁ Hollow polished steel pin.

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⦁ Attached in a variety of ways.

⦁ Pinned to piston.

⦁ Clamped to rod small end.

⦁ Snap ring free floating.

⦁ Press fit.

Connecting rods:

⦁ I-beam style rod use to transfer the pistons force to the crankshaft.

⦁ Small end contains the piston pin and the big end has a removable cap to install it to

the Crank.

⦁ Nuts and bolts are usually of a very high quality.

Installation of pistons:

⦁ Cylinder number

⦁ Piston number

⦁ Notch to the front

⦁ Position ring gaps

⦁ Remove rod cap check bearing inserts

⦁ Cover bolts with fuel line if needed

⦁ Crankshaft at TDC or BDC

⦁ Install ring compressor

⦁ Oil piston, cylinder wall, & crank journal

⦁ Carefully tap in piston with hammer handle.

⦁ Properly replace rod cap

Automotive chassis:

Introduction of Chassis Frame: Chassis is a French term and was initially used to denote

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the frame parts or Basic Structure of the vehicle. It is the back bone of the vehicle. A vehicle with out body is called Chassis. The components of the vehicle like Power plant, Transmission System, Axles, Wheels and Tyres, Suspension, Controlling Systems like Braking, Steering etc., and also electrical system parts are mounted on the Chassis frame. It is the main mounting for allthe components including the body. So it is also called as Carrying Unit.

The following main components of the Chassis are1. Frame: it is made up of long two members called side member riveted together with the help of number of cross members.2. Engine or Power plant: It provides the source of power3. Clutch: It connects and disconnects the power from the engine fly Wheel to the transmission system.4. Gear Box 5.U Joint 6. Propeller Shaft 7. Differential

FUNCTIONS OF THE CHASSIS FRAME:1. To carry load of the passengers or goods carried in the body.2. To support the load of the body, engine, gear box etc.,3. To withstand the forces caused due to the sudden braking or acceleration4. To withstand the stresses caused due to the bad road condition.5. To withstand centrifugal force while corneringTYPES OF CHASSIS FRAMES:There are three types of frames1. Conventional frame2. Integral frame3. Semi-integral frame

1. Conventional frame: It has two long side members and 5 to 6 cross members joined together with the help of rivets and bolts. The frame sections are used generally.a. Channel Section - Good resistance to bendingb. Tabular Section - Good resistance to Torsionc. Box Section - Good resistance to both bending and Torsion

2. Integral Frame: This frame is used now days in most of the cars. There is no frame and all the assembly units are attached to the body. All the functions of the frame carried out by the body itself. Due to elimination of long frame it is cheaper and due to less weight most economical also. Only disadvantage is repairing is difficult.

3. Semi - Integral Frame: In some vehicles half frame is fixed in the front end on which engine gear box and front suspension is mounted. It has the advantage when the vehicle is met with accident the front frame can be taken easily to replace the damaged chassis frame. This type of frame is used in FIAT cars and some of the European and American cars.

VARIOUS LOADS ACTING ON THE FRAME:

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Various loads acting on the frame are1. Short duration Load - While crossing a broken patch.2. Momentary duration Load - While taking a curve.3. Impact Loads - Due to the collision of the vehicle.4. Inertia Load - While applying brakes.5. Static Loads - Loads due to chassis parts.6. Over Loads - Beyond Design capacity.

STATE THE DIFFERENT BODIES USED IN AUTOMOBILES:The Automobile bodies are divided in two groups

⦁ Passenger Body

⦁ Commercial body

REQUIREMENTS OF BODIES FOR VARIOUS TYPES OF VECHILE:The body of the most vehicle should fulfill the following requirements:1. The body should be light.2. It should have minimum number of components.3. It should provide sufficient space for passengers and luggage.4. It should withstand vibrations while in motion.5. It should offer minimum resistance to air.6. It should be cheap and easy in manufacturing.7. It should be attractive in shape and color.8. It should have uniformly distributed load.9. It should have long fatigue life.10. It should provide good vision and ventilation.

Unit 2

Engine Auxiliary systems

Gasoline Electronic Fuel Injection System:

A modern gasoline injection system uses pressure from an electric fuel pump to spray fuel into

the engine intake manifold. Like a carburetor, it must provide the engine with the correct air-

fuel mixture for specific operating conditions. Unlike a carburetor, however, PRESSURE, not

engine vacuum, is used to feed fuel into the engine. This makes the gasoline injection

system very efficient.

A gasoline injection system has several possible advantages over a carburetor type of fuel

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system.

Some advantages are as follows:

1. Improved atomization. Fuel is forced into the intake manifold under pressure that helps

break fuel droplets into a fine mist.

2. Better fuel distribution. Equal flow of fuel vapors into each cylinder.

3. Smoother idle. Lean fuel mixture can be used without rough idle because of better fuel

distribution and low-speed atomization.

* Lower emissions. Lean efficient air-fuel mixture reduces exhaust pollution.

* Better cold weather drivability. Injection provides better control of mixture enrichment

than a carburetor.

* Increased engine power. Precise metering of fuel to each cylinder and increased air flow

can result in more horsepower output.

* Fewer parts. Simpler, late model, electronic fuel

injection system have fewer parts than modern computer-controlled carburetors

Types:

* single- or multi-point injection

* indirect or direct injection

The point or location of fuel injection is one way to classify a gasoline injection system. A single-

point injection system, also call throttle body injection (TBI), has the injector nozzles in a

throttle body assembly on top of the engine. Fuel is sprayed into the top center of

the intake manifold .

A multi-point injection system, also called port injection, has an injector in the port (air-fuel

passage) going to each cylinder. Gasoline is sprayed into each intake port and toward each

intake valve. Thereby, the term multipoint (more than one location) fuel injection is used

System component:

⦁ Fuel tank

⦁ Electric fuel pump

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⦁ Fuel filter

⦁ Electronic control unit

⦁ Common rail and Pressure sensor

⦁ Electronic Injectors

⦁ fuel line

Fuel Tank:

⦁ is safe container for flammable liquids and typically part of an engine system in which

the fuel is stored and propelled (fuel pump) or released (pressurized gas) into an

engine.

⦁ Typically, a fuel tank must allow or provide the following:

⦁ Safe (UL Approved) fuel storage, there is some concern that UL (Underwriters

Laboratories) is not the final arbiter of safety.

⦁ Filling (the fuel tank must be filled in a secure way) No Sparks.

⦁ Storage of fuel (the system must contain a given quantity of fuel and must avoid

leakage and limit evaporative emissions)

⦁ Provide a method for determining level of fuel in tank, Gauging (the remaining quantity

of fuel in the tank must be measured or evaluated)

⦁ Venting (if over-pressure is not allowed, the fuel vapors must be managed through

valves)

⦁ Feeding of the engine (through a pump)

⦁ Anticipate potentials for damage and provide safe survival potential.

Electronic fuel pump:

⦁ An electric fuel pump is used on engines with fuel injection to pump fuel from the tank

to the injectors. The pump must deliver the fuel under high pressure (typically 30 to 85

psi depending on the application) so the injectors can spray the fuel into the engine.

⦁ Electric fuel pumps are usually mounted inside the fuel tank,

⦁ Some vehicles may even have two fuel pumps (a transfer pump inside the tank, and a

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main fuel pump outside).

⦁ An electric fuel pump is used on engines with fuel injection to pump fuel from the tank

to the injectors. The pump must deliver the fuel under high pressure (typically 30 to 85

psi depending on the application) so the injectors can spray the fuel into the engine.

⦁ Electric fuel pumps are usually mounted inside the fuel tank,

⦁ Some vehicles may even have two fuel pumps (a transfer pump inside the tank, and a

main fuel pump outside).

Most newer vehicles use a "turbine" style fuel pump. A turbine pump has an impeller ring

attached to the motor. The blades in the impeller push the fuel through the pump as the

impeller spins. This type of pump is not a positive-displacement pump, so it produces no

pulsations, runs very smoothly and quietly. It is also less complicated to manufacture and is very

durable. Some aftermarket pump supplies use this type of pump to replace the older designs.

Fuel Filter:

⦁ The fuel filter is the fuel system's primary line of defense against dirt, debris and small

particles of rust that flake off the inside of the fuel tank.

⦁ Many filters for fuel injected engines trap particles as small as 10 to 40 microns in size.

⦁ Fuel filter normally made into cartridges containing a filter paper.

Electronic Control Circuit:

⦁ In automotive electronics, electronic control unit (ECU) is a generic term for any

embedded system that controls one or more of the electrical systems or subsystems in

a motor vehicle.

⦁ An engine control unit (ECU), also known as power-train control module (PCM), or

engine control module (ECM) is a type of electronic control unit that determines the

amount of fuel, ignition timing and other parameters an internal combustion engine

needs to keep running. It does this by reading values from multidimensional maps

which contain values calculated by sensor devices monitoring the engine.

Working of ECU:

⦁ Control of fuel injection: ECU will determine the quantity of fuel to inject based on a

number of parameters. If the throttle pedal is pressed further down, this will open the

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throttle body and allow more air to be pulled into the engine. The ECU will inject more

fuel according to how much air is passing into the engine. If the engine has not warmed

up yet, more fuel will be injected.

⦁ Control of ignition timing: A spark ignition engine requires a spark to initiate

combustion in the combustion chamber. An ECU can adjust the exact timing of the

spark (called ignition timing) to provide better power and economy.

⦁ Control of idle speed: Most engine systems have idle speed control built into the ECU.

The engine RPM is monitored by the crankshaft position sensor which plays a primary

role in the engine timing functions for fuel injection, spark events, and valve timing. Idle

speed is controlled by a programmable throttle stop or an idle air bypass control

stepper motor.

Common rail and Pressure sensor:

⦁ The fuel injectors are typically ECU-controlled. When the fuel injectors are electrically

activated a hydraulic valve (consisting of a nozzle and plunger) is mechanically or

hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since

the fuel pressure energy is stored remotely and the injectors are electrically actuated

the injection pressure at the start and end of injection is very near the pressure in the

accumulator (rail), thus producing a square injection rate. If the accumulator, pump,

and plumbing are sized properly, the injection pressure and rate will be the same for

each of the multiple injection events.

⦁ The term "common rail" refers to the fact that all of the fuel injectors are supplied by a

common fuel rail which is nothing more than a pressure accumulator where the fuel is

stored at high pressure. This accumulator supplies multiple fuel injectors with high

pressure fuel.

Electronic injectors:

⦁ The injectors can survive the excessive temperature and pressure of combustion by

using the fuel that passes through it as a coolant

⦁ The electronic fuel injector is normally closed, and opens to inject pressurized fuel

as long as electricity is applied to the injector's solenoid coil.

⦁ When the injector is turned on, it opens, spraying atomized fuel at the combustion

chamber. Depending on engine operating condition ,injection quantity will vary.

Fuel line:

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⦁ Fuel line hoses carry gasoline from the tank to the fuel pump, to the fuel filter, and

to the fuel injection system. While much of the fuel lines are rigid tube, sections of

it are made of rubber hose, which absorb engine and road vibrations.

⦁ There are two basic types of fuel hose: Fuel and oil hoses that meet the SAE 30R7

standard, and fuel injection hose that meets the requirements of SAE 30R9.

Gasoline direct injection:

⦁ In internal combustion engines, gasoline direct injection is a variant of fuel injection

employed in modern two- and four- stroke petrol engines. The petrol/gasoline is highly

pressurized, and injected via a common rail fuel line directly into the combustion

chamber of each cylinder, as opposed to conventional multi-point fuel injection that

happens in the intake tract, or cylinder port.

Gasoline direct injection:

⦁ When the driver turns the ignition key on, the power train control module (PCM)

energizes a relay that supplies voltage to the fuel pump. The motor inside the pump

starts to spin and runs for a few seconds to build pressure in the fuel system. A timer in

the PCM limits how long the pump will run until the engine starts.

⦁ Fuel is drawn into the pump through an inlet tube and mesh filter sock

⦁ The fuel then exits the pump through a one-way check valve and is pushed toward the

engine through the fuel line and filter.

⦁ The fuel filter traps any rust, dirt or other solid contaminants that may have passed

through the pump to prevent such particles from clogging the fuel injectors.

⦁ The fuel then flows to the fuel supply rail on the engine and is routed to the individual

fuel injectors. A fuel pressure regulator on the fuel rail maintains fuel pressure, and

recirculates excess fuel back to the tank.

⦁ The fuel pump runs continuously once the engine starts, and continues to run as long as

the engine is running and the ignition key is on. If the engine stalls, the (PCM) will detect

the loss of the RPM signal and turn the pump off.

Unit-3

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Transmission systems

Front wheel drive:

⦁ Most automobiles today have front-wheel drive

⦁ FWD car has transaxle

⦁ Drive axles extend to front wheels out of each side of transaxle

⦁ Each end of the drive axle is a CV joint

⦁ Transaxle can be either manual or automatic

⦁ Advantages

⦁ More efficient drivetrain

⦁ Better fuel economy

⦁ Combined with MacPherson struts: less unsprung weight for better handling

⦁ Transmission hump is eliminated

⦁ A few FWD engines have been mounted longitudinally

⦁ Most transaxles mounted sideways

Manual Transaxle:

⦁ Manual transaxles and transmissions

⦁ Use same kind of clutch

⦁ Three parallel paths for power flow

⦁ Input shaft located above intermediate shaft

⦁ Input shaft gears directly drive output shaft gears

⦁ Differential assembly

⦁ Gear shafts

⦁ Supported by larger ball, roller, or tapered roller bearings

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⦁ End play is controlled by thrust washers

Shift linkage:

⦁ Transverse transaxles

⦁ Shifted by cables or shift linkage

⦁ Two shift cables or rods

⦁ One moves a selector on transaxle

⦁ Other moves shift fork back and forth

⦁ Advantage

⦁ Engine shake is not transmitted back to driver’s hand on shift lever

Transaxle differential:

⦁ Allows wheels to turn at different speeds when rounding corners

⦁ Same as rear-wheel-drive differential

⦁ Ordinary helical gearset

⦁ Used instead of bevel gears

⦁ Power from differential side gears is transmitted to front drive axles through

axle shafts

Transaxle power flow:

⦁ Five-speed power flow

⦁ Fixed gears for first, second, and reverse on input shaft

⦁ Fixed gears for third, fourth, fifth on intermediate shaft

⦁ Power flow leaves transmission intermediate shaft

⦁ Continues through drive pinion to axles

⦁ Engine is mounted sideways

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⦁ Axles run parallel to input shaft

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Automatic transaxle:

⦁ Combination of automatic transmission and differential

⦁ Same parts and operation apply

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⦁ Transverse engine

⦁ Power flow is through gears or sprocket and chain

⦁ Chain drive

⦁ Allows transaxle to be mounted slightly below and to the side of the engine

Front drive axles:

⦁ Difference between rear-wheel drive and front-wheel drive axles

⦁ Front-wheel drive axles have CV joints at ends

⦁ Axles driven at sharper angles

⦁ Allow steering front wheels during power transmission

⦁ Universal joint changes output speed twice in every revolution when run at an

angle

⦁ Rear-wheel drive vehicle drive shaft turns very fast

⦁ Positioned before gear reduction of differential

Axle shaft parts:

⦁ Drive axle is called half shaft or axle shaft

⦁ Stub shaft (stub axle)

⦁ Short shaft at outside end

⦁ Splined to front hub so it can drive front wheels

⦁ CV joint classifications

⦁ Inboard and outboard

⦁ Fixed and plunge

⦁ Ball and tripod

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Axle shafts:

⦁ Characteristics

⦁ May be solid or hollow

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⦁ May have damper weights to absorb vibration

⦁ Turn much slower than rear-wheel drive shaft

⦁ Balance not as important

⦁ When different lengths: long one twists and lags before puts its torque to

the wheel

⦁ Torque steer is prevented by longer axle shaft of larger diameter

tubing

CV joint boots:

⦁ Boots at each end of axle contain grease

⦁ Protect joint from the elements

⦁ CV joint boot

⦁ Attached to axle and stub shafts with plastic or steel bands or straps

⦁ Made of natural rubber, neoprene, silicone, or urethane

Unit 4

Steering, Brakes and Suspension systems

Steering systems:

⦁ Any mode of transportation used by people must have some means of control. For the

automobile, two primary control systems are at the driver's disposal: (1) the steering

system, and (2) the braking system.

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⦁ The steering mechanism converts the driver's rotational input at the steering wheel into

a change in the steering angle of the vehicle's steering road wheels.

⦁ For a car to turn smoothly, each wheel must follow a different circle. Since the inside

wheel is following a circle with a smaller radius, it is actually making a tighter turn than

the outside wheel. If you draw a line perpendicular to each wheel, the lines will

intersect at the center point of the turn. The geometry of the steering linkage makes

the inside wheel turn more than the outside wheel.

⦁ Steering behavior

⦁ The requirements in terms of steering behavior can be summarized as follows:

⦁ 1. Jolts from irregularities in the road surface must be damped as much as possible

during transmission to the steering wheel. However, such damping must not cause the

driver to lose contact with the road.

⦁ 2. The basic design of the steering kinematics must satisfy the Ackermann conditions:

the extensions of the wheel axes of the left and right front wheels, when at an angle,

intersect on an extension of the rear axle.

⦁ 3. When the steering wheel is released, the wheels must return automatically to the

straight-ahead position and must remain stable in this position.

⦁ 4. The steering should have as Iow ratio as possible (number of steering-wheel turns

from lock to lock) in order to obtain ease of handling. The steering forces involved are

determined not only by the steering ratio but also by the front suspension load, the

turning circle, the suspension geometry (caster angle, kingpin angle, kingpin offset), the

properties of the tire tread and the road surface.

⦁ The steering ratio is the ratio of how far you turn the steering wheel to how far the

wheels turn. For instance, if one complete revolution (360 degrees) of the steering

wheel results in the wheels of the car turning 20 degrees, then the steering ratio is 360

divided by 20, or 18:1. A higher ratio means that you have to turn the steering wheel

more to get the wheels to turn a given distance. However, less effort is required

because of the higher gear ratio.

⦁ Generally, lighter, sportier cars have lower steering ratios than larger cars and trucks.

The lower ratio gives the steering a quicker response -- you don't have to turn the

steering wheel as much to get the wheels to turn a given distance -- which is a desirable

trait in sports cars. These smaller cars are light enough that even with the lower ratio,

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the effort required to turn the steering wheel is not excessive.

⦁ Some cars have variable-ratio steering, which uses a rack-and-pinion gearset that has a

different tooth pitch (number of teeth per inch) in the center than it has on the outside.

This makes the car respond quickly when starting a turn (the rack is near the center),

and also reduces effort near the wheel's turning limits.

Linkage steering system (worm) gear parts:

⦁ Steering Wheel – used by the driver to rotate a steering shaft that passes through the

steering column.

⦁ Steering Shaft – transfers turning motion from the steering wheel to the steering

gearbox.

⦁ Steering Column – supports the steering column and steering shaft.

⦁ Steering gears are enclosed in a casing known as steering gear box.

⦁ A steering box must have the following qualities:

⦁ - no play in the straight-ahead position,

⦁ -low friction, resulting in high efficiency,

⦁ - high rigidity,

⦁ - readjustability.

⦁ For these reasons, two types have become established:

Rack and pinion streering:

⦁ Basically, as the name implies, the rack-and-pinion steering consists of a rack and a

pinion, The steering ratio is defined by the ratio of pinion revolutions (steering-¬wheel

revolutions) to rack travel. Suitable toothing of the rack allows the ratio to be made

variable over the travel. This lowers the actuating force or reduces the travel for

steering corrections.

⦁ Rack-and-pinion steering is quickly becoming the most common type of steering on

cars, small trucks. It is actually a pretty simple mechanism. A rack-and-pinion gearset is

enclosed in a metal tube, with each end of the rack protruding from the tube. A rod,

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called a tie rod, connects to each end of the rack.

⦁ The pinion gear is attached to the steering shaft. When you turn the steering wheel,

the gear spins, moving the rack.

⦁ The rack-and-pinion gearset does two things:

⦁ It converts the rotational motion of the steering wheel into the linear motion needed to

turn the wheels.

⦁ It provides a gear reduction, making it easier to turn the wheels.

⦁ On most cars, it takes three to four complete revolutions of the steering wheel to make

the wheels turn from lock to lock (from far left to far right).

⦁ The primary components of the rack and pinion steering system are:

⦁ Rubber bellows

⦁ Pinion

⦁ Rack

⦁ Inner ball joint or socket

⦁ Tie-rod

Rubber Bellows:

⦁ This rubber bellows is attached to the Rack and Pinion housing. It protects the inner

joints from dirt and contaminants. In addition, it retains the grease lubricant inside the

rack and pinion housing. There is an identical bellows on the other end of the rack for

the opposite side connection.

Pinion:

⦁ The pinion is connected to the steering column. As the driver turns the steering

wheel, the forces are transferred to the pinion and it then causes the rack to move

in either direction. This is achieved by having the pinion in constant mesh with the

rack.

Rack:

⦁ The rack slides in the housing and is moved by the action of the meshed pinion into the

teeth of the rack. It normally has an adjustable bush opposite the pinion to control their

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meshing, and a nylon bush at the other end.

Inner ball or socket:

⦁ The inner ball joint is attached to the tie-rod, to allow for suspension movement

and slight changes in steering angles

Tie rod:

⦁ A tie rod end is attached to the tie-rod shaft. These pivot as the rack is extended or

retracted when the vehicle is negotiating turns. Some tie-rods and tie-rod ends are left

or right hand threaded. This allows toe-in or toe-out to be adjusted to the

manufacturer's specifications.

Toe:

⦁ Toe is defined as the difference of the distance between the leading edge of the wheels

and the distance between the trailing edge of the wheels when viewed from above.

Toe-in means the front of the wheels are closer than the rear; toe-out implies the

opposite. Figure 7.20 shows both cases.

⦁ For a rear-wheel-drive vehicle, the front wheels normally have a slight amount of toe-

in.. When the vehicle begins to roll, rolling resistance produces a force through the tire

contact patch perpendicular to the rolling axis. This force produces a torque around the

steering axis that tends to cause the wheels to toe-out. The slight toe-in allows for this,

and when rolling, the wheels align along the axis of the vehicle. Conversely, front-

wheel-drive vehicles require slight toe out. In this case, the tractive force of the front

wheels produces a moment about the steering axis that tends to toe the wheels inward.

In this case, proper toe-out absorbs this motion and allows the wheels to parallel the

direction of motion of the vehicle.

Power rack and pinion:

⦁ When the rack-and-pinion is in a power-steering system, the rack has a slightly different

design.

⦁ Part of the rack contains a cylinder with a piston in the middle. The piston is connected

to the rack. There are two fluid ports, one on either side of the piston. Supplying higher-

pressure fluid to one side of the piston forces the piston to move, which in turn moves

the rack, providing the power assist.

Re- circulating ball streering:

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⦁ The forces generated between steering worm and steering nut are transmitted via a

low-friction recirculating row of balls. The steering nut acts on the steering shaft via

gear teeth. A variable ratio is possible with this steering box,

⦁ Recirculating-ball steering is used on many trucks and SUVs today. The linkage that

turns the wheels is slightly different than on a rack-and-pinion system.

⦁ The recirculating-ball steering gear contains a worm gear. The first part is a block of

metal with a threaded hole in it. This block has gear teeth cut into the outside of it,

which engage a gear that moves the pitman arm (see diagram above). The steering

wheel connects to a threaded rod, similar to a bolt, that sticks into the hole in the block.

When the steering wheel turns, it turns the bolt. Instead of twisting further into the

block the way a regular bolt would, this bolt is held fixed so that when it spins, it moves

the block, which moves the gear that turns the wheels.

⦁ Instead of the bolt directly engaging the threads in the block, all of the threads are filled

with ball bearings that recirculate through the gear as it turns. The balls actually serve

two purposes: First, they reduce friction and wear in the gear; second, they reduce slop

in the gear. Slop would be felt when you change the direction of the steering wheel --

without the balls in the steering gear, the teeth would come out of contact with each

other for a moment, making the steering wheel feel loose.

⦁ Power steering in a recirculating-ball system works similarly to a rack-and-pinion

system. Assist is provided by supplying higher-pressure fluid to one side of the block.

⦁ Power steering helps drivers steer vehicles by increasing steering effort of the steering

wheel. Hydraulic or electric actuators add controlled energy to the steering mechanism,

so the driver needs to provide only slight effort regardless of conditions. Power steering

helps considerably when a vehicle is stopped or moving slowly. As well, power steering

provides some feedback of forces acting on the front wheels to give an ongoing sense

of how the wheels are interacting with the road; this is typically called "rοad feel"·

⦁ Representative power steering systems for cars increase steering effort via an actuator,

a hydraulic cylinder, which is part of a servo system. These systems have a direct

mechanical connection between the steering wheel and the linkage that steers the

wheels. This means that power-steering system failure still permits the vehicle to be

steered using manual effort alone.

⦁ In other power steering systems, electric motors provide the assistance instead of

hydraulic systems. As with hydraulic types, power to the actuator (motor, in this case) is

controlled by the rest of the power-steering system.

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⦁ Some construction vehicles have a two-part frame with a rugged hinge in the middle;

this hinge allows the front and rear axles to become non-parallel to steer the vehicle.

Opposing hydraulic cylinders move the halves of the frame relative to each other to

steer.

Hydraulic power assisted steering:

⦁ Energy source

⦁ The energy source consists of a vane pump (generally driven by the engine) with

an integral oil-flow regulator, an oil reservoir and connecting hoses and pipes.

⦁ The pump must be dimensioned so that it generates sufficient pressure to enable

rotation of the steering wheel at a speed of at least 15 m/s even when the engine is

only idling.

⦁ The compulsory pressure-limiting valve required on hydraulic systems is usually

integrated. .

⦁ The pump and the system components must be designed such that the operating

temperature of the hydraulic fluid does not rise to an excessive level (<100°C) and

such that no noise is generated and the oil does not foam.

Control Valve:

⦁ All power steering pumps have a flow-control valve to vary fluid flow and power

steering system pressures. A pressure relief valve prevents excessive pressures

developing when the steering is on full-lock, and held against its stops. The flow control

valve is located at the outlet fitting of the pump.

⦁ During slow cornering, or when parking, pump speeds are normally low. There is less

demand for fluid flow, but to provide the required assistance, high pressure is needed.

Discharge ports direct the fluid to the outlet, and then to the steering gear. The outlet

fluid pressure is slightly lower than the internal high pressure coming from the pump.

Pump:

⦁ The hydraulic power for the steering is provided by a rotary-vane pump. This pump is

driven by the car's engine with a belt and pulley. It contains a set of retractable vanes

that spin inside an oval chamber.

⦁ As the vanes spin, they pull hydraulic fluid from the return line at low pressure and

force it into the outlet at high pressure. The amount of flow provided by the pump

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depends on the car's engine speed. The pump must be designed to provide adequate

flow when the engine is idling. As a result, the pump moves much more fluid than

necessary when the engine is running at faster speeds.

⦁ The pump contains a pressure-relief valve to make sure that the pressure does not get

too high, especially at high engine speeds when so much fluid is being pumped.

Rotary Valve:

⦁ A power-steering system should assist the driver only when he is exerting force on the

steering wheel (such as when starting a turn). When the driver is not exerting force

(such as when driving in a straight line), the system shouldn't provide any assist. The

device that senses the force on the steering wheel is called the rotary valve.

Electric power assisted with pull drift :

Pull-Drift Compensation starts with EPAS technology, which replaces the traditional hydraulic-

assist powersteering pump with an electric motor. This increases fuel economy because the

electric motor operates only when steering assistance is required.

Sensors constantly measure steering wheel torque applied by the driver to

maintain the vehicle’s path. Continuous adjustments are made as the system resets to adapt to

changing road conditions or maneuvers, such as the vehicle turning a corner.

When the system detects a pulling or drifting condition, such as a crowned

road surface, it provides torque assistance to help make steering easier. For drivers, this

assistance is seamless and imperceptible.

EPAS technology can be fine-tuned by engineers to fit the driving characteristics

of varying products, whether it’s a luxury sedan or sporty compact SUV.

Unit-5

ALTERNATIVE ENERGY SOURCES

Alternative fuels:

As the cost of conventional fuels goes up, the interest in other fuel sources increase.

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In some cases, alternative fuels are more environmentally friendly. Some alternative

fuels are more energy efficient

Types of alternative fuels:

⦁ Ethanol

⦁ Natural gas

⦁ Propane

⦁ Hydrogen

⦁ Biodiesel

⦁ Electricity

⦁ Methanol

Ethanol:

⦁ Ethanol is an alcohol-based alternative fuel produced by fermenting and distilling

starch crops or cellulose that have been converted into simple sugars

⦁ Ethanol is most commonly used to increase octane and improve the emissions

quality of gasoline.

⦁ Ethanol can be blended with gasoline to create E85, a blend of 85% ethanol and

15% gasoline.

⦁ Ethanol can degrade quickly in water, therefore, posing less environmental harm

than oil in the case of a spill

⦁ Ethanol is an excellent, clean-burning fuel, potentially providing more horsepower

than gasoline. In fact, ethanol has a higher octane rating (over 100) and burns

cooler than gasoline

⦁ One acre of corn can produce 300 gal. Of ethanol per growing season. So, in order

to replace that 200 billion gal. Of petroleum products, American farmers would

need to dedicate 675 million acres, or 71 percent of the nation's 938 million acres

of farmland, to growing feedstock.

Natural gas:

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⦁ Natural gas is produced either from gas wells

⦁ Or in conjunction with crude oil production.

⦁ Because of the gaseous nature of this fuel, it must be stored onboard a vehicle in

either a compressed gaseous state or in a liquefied state

⦁ A natural gas vehicle can be less expensive to operate than a comparable

conventionally fueled vehicle depending on natural gas prices.

⦁ The United States has vast natural gas reserves across the country

⦁ Vehicles tend to cost $3500 to $6000 more than gasoline powered ones

Propane:

⦁ Propane or liquefied petroleum gas (LPG) is a

⦁ Popular alternative fuel choice for vehicles because there is already an

infrastructure of pipelines, processing facilities, and storage for its efficient

distribution.

⦁ LPG produces fewer vehicle emissions than gasoline.

⦁ Propane is produced as a by-product of natural gas processing and crude oil

refining.

⦁ Propane vehicles can produce fewer ozone-forming emissions than vehicles

powered by reformulated gasoline

⦁ The cost of a gasoline-gallon equivalent of propane is generally less than that of

gasoline, so driving a propane vehicle can save money.

⦁ Hydrogen, a gas, will play an important

⦁ role in developing sustainable transportation

⦁ In the United States, because in the future it may be produced in virtually

unlimited quantities using renewable resources.

Hydrogen:

⦁ Hydrogen and oxygen from air fed into a proton exchange membrane fuel cell

produce enough electricity to power an electric automobile, without producing

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harmful emissions. The only byproduct of a hydrogen fuel cell is water.

⦁ Currently there are no original equipment manufacturer vehicles available for sale

to the general public. Experts estimate that in approximately 10-20 years hydrogen

vehicles, and the infrastructure to support them, will start to make an impact.

Bio diesel:

⦁ Biodiesel is a domestically produced, renewable fuel that can be manufactured

from vegetable oils, animal fats, or recycled restaurant greases.

⦁ Biodiesel is safe, biodegradable, and reduces serious air pollutants such as

particulates, carbon monoxide, hydrocarbons, and air toxics.

⦁ Biodiesel can also be used in its pure form but it may require certain engine

modifications to avoid maintenance and performance problems and may not be

suitable for wintertime use.

⦁ Pure biodiesel, B100, costs about $3.50--roughly a dollar more per gallon than

petro diesel.

⦁ Need to heat storage tanks in colder climates to prevent the fuel from gelling

⦁ Like E85, biodiesel began with farm co-ops and local entrepreneurs. High fuel

prices affect farmers, too, and here was an opportunity to make money from

otherwise fallow farmland

Electricity:

⦁ Electricity can be used as a transportation fuel to power battery electric and fuel

cell vehicles. When used to power electric vehicles, electricity is stored in an

energy storage device such as a battery.

⦁ EV batteries have a limited storage capacity and their electricity must be

replenished by plugging the vehicle into an electrical source.

⦁ EVs have lower "fuel" and maintenance costs than gasoline-powered vehicles.

⦁ Vehicles that operate only on electricity require no warm-up, run almost silently

and have excellent performance up to the limit of their range. Also, electric cars

are cheap to "refuel." At the average price of 10 cents per kwh, it costs around 2

cents per mile. Pure electric cars still have limited range, typically no more than

100 to 120 miles.

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Methanol:

⦁ Methanol, also known as wood alcohol, can be used as an alternative fuel in

flexible fuel vehicles that run on M85

⦁ It is not a commonly used fuel at this time as methanol produces a high amount of

formaldehyde in emissions.

⦁ The benefits include lower emissions, higher performance, and lower risk of

flammability than gasoline. Methanol can easily be made into hydrogen for

hydrogen fuel cell vehicles in the future

⦁ Methanol is extremely corrosive, requiring special materials for delivery and

storage. Methanol, in addition, has only 51 percent of the BTU content of gasoline

by volume, which means its fuel economy is worse than ethanol's.

⦁ Methane also can be produced by processing biomass such as grass clippings,

sawdust and other cellulose sources.

DEPARTMENT OF MECHANICAL ENGINEERING

QUESTION BANK

Subject Name: ME2354- AUTOMOBILE ENGINEERING

Year/Sem: III / VI

UNIT-I VEHICLE STRUCTURE AND ENGINES

PART A (2 MARKS)

1. State major types of automobiles according to the fuel used.

2. List any four components of a chassis.

3. Mention any two requirement of an automobile.

4. List any four characteristics of a good chassis.

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5. Give any two requirement of good frame.

6. Define cross wind force.

7. State any four functions of lubrication.

8. State purpose of providing radiator in cooling systems.

9. Name any four air pollutants.

10. What do you mean by Electronic Engine Management system?

PART B (16 MARKS )

01. Explain the construction of various frames used in automobiles with neat

sketch. (16)

02. Discuss the Construction and working principles of 3-way Catalytic

controller (16)

03. Explain the following terms :

Load distribution in frames

Frame types with neat sketch

Frame materials

Frame testing. (16)

04. i) Explain the operation of the typical turbocharger with sketch. (8)

ii) Discuss the principle of operation of a four stroke cycle S.I. Engine with a neat sketch.

(8)

05. With the help of neat sketch explain in detail about the construction and

working of different engine components? (16)

06. i) What are the functions of a cooling system? (2)

ii) Sketch and explain different types of lubrication systems used in

automotive engines. (14)

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07. i) What do you know about emission norms? Discuss. (7)

ii) With a block diagram discuss the operational features of electronics engine

management system. (9)

08. i) What are the desirable properties of a good lubricant? (8)

ii) Draw the layout of an automobile and indicate the various components. (8)

09. Discuss various methods to reduce the level of pollutants in the exhaust gases. (16)

UNIT II

ENGINE AUXILLARY SYSTEM

PART A (2 MARKS)

1. What is carburetor?

2. What are the requirements of a spark plug?

3. List out the main functions of a battery.

4. What is a variable jet carburetor?

5. What is the function of ORC in a start ing motor?

6. Name the components of battery coil ignition system used in vehicle.

7. What is the purpose of Cut-out relay?

8. What are the important units electronic fuel injection system?

9. Mention the two ways of determining the stste of charge.

10. What are the factors to be considered for comparing magneto and coil ignition system?

PART B (16 MARKS )

01. Briefly discuss the working principle of a simple Carburator system. (16)

02. Describe the construction and working principles of Battery-Coil ignition

system. (16)

03. i) What is carburetion? Explain principle of carburetor. (8)

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ii) With suitable sketch explain the principle of the MPFI. (8)

04. i) Explain CDI ignition system with a suitable diagram. (8)

ii) Sketch and explain the starting circuit of the cranking motor. (8)

05. i) Differentiate Electronic Fuel Injection system from Conventional Fuel

Injection system. (4)

ii) Describe about Multi Point Fuel Injection System of an automotive engine.

(12)

06. With the help of neat sketches explain in detail about Battery, Magneto coil

and Electronic Ignition Systems. (16)

07. i) Discuss the construction, operation and maintenance of lead acid battery. (8)

ii) Explain the different tests conducted to assertain the condition of the battery. (8)

08. With suitable sketches explain mono point and multi point fuel injection systems and

bring out the comparative features. (16)

09. i) Explain the working features of a starter motor with a neat diagram. (8)

ii) Explain the operation of a MPFI system and compare it with TBI system. (8)

UNIT III

TRANSMISSION SYSTEM

PART A (2 MARKS)

1. What are the function of clutch?

2. What is the function of Synchromesh unit in a gear box?

3. State the function of differential unit.

4. What are the functions of universal joint?

5. List out the functions of a propeller shaft.

6. Why epicyclic gears are used in overdrive units?

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7. Classify gear box.

8. Why is double cluching technique used?

9. How torque converter gearbox differs from fluid flywheel?

10. State the phenomenon of torque multiplication.

PART B (16 MARKS )

01. Explain the construction and working principles of a typical automobile

gear box. (16)

02. Discuss the working principles of

(i) Torque tube drive. (8)

(ii) Hotchkiss drive. (8)

03. i) What is clutch? Explain the operation of centrifugal clutch. (8)

ii) Explain the working principle and application of a freewheel drive in a

transmission system. (8)

04. i) Explain different type of rear axles with neat sketch. (10)

ii) What is differential? Explain its operation with sketch. (6)

05. Explain in detail about any one type of Synchromesh Gear Box wi th neat

sketches. (16)

06. i) What are the effects of wheel bearing layout on axle loading? (8)

ii) What do you mean by double reduction axle? Explain in detail (8)

07. i) What are the features of a good quality clutch? Explain the working of multi plate

clutch

with a neat sketch. (12)

ii) What is the function of a clutch? List out the requirement of a clutch. (4)

08. Discuss the fully floating axle and three-quarter floating axle with neat sketches. (16)

09. Explain with suitable sketches the operational features of sliding mesh gearbox. (16)

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UNIT IV

STEERING BRAKES AND SUSPENSION

PART A (2 MARKS)

1. List out the types of front axle.

2. What is meant by bleeding of brakes?

3. Classify independent rear suspension system.

4. What are the functions of suspension system?

5. Define slip angle.

6. Define overall steering ratio.

7. What is meant by centre point steering?

8. Define caster angle.

9. What is meant by term ‘tread’?

10. Compare the advantages of radial tyre over cross ply tyre.

PART B (16 MARKS )

01. Sketch and explain the working of power steering system. (16)

02. Explain the working principles of Hydraulic braking system with simple

sketches. (16)

03. i) Sketch and explain various steering geometries. (8)

ii) Describe with the help of simple diagram the different type of stub axles. (8)

04. i) Give short note on leaf spring suspension system. (4)

ii) Explain the operation of Hydraulic braking system with neat sketch. (12)

05. With the aid of neat sketches, Explain in detail about construction and

working of disk brake system. (16)

06. Explain in detail about a typical front suspension wi th neat sketches. (16)

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07. i) Discuss air suspension system with a sketch. (8)

ii) How wheel alignment done in automobiles? Explain. (8)

08. i) Explain with the help of a suitable sketch the construction of the disc wheel. (8)

ii) Draw and explain the cross section of an automobile tyre. (8)

09. Discuss the construction details of leaf, coil and torsion bar springs. (16)

10. Sketch and explain a typical power steering gear box and compare it with ordinary

steering system. (16)

11. Discuss the working of telescopic suspension system used in cars. (16)

UNIT V

ALTERNATIVE ENERGY SOURCES

PART A (2 MARKS)

1. What is meant by a fuel cell and how it works?

2. List down the properties of alternate fuels.

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3. State any two advantages of methane as fuel in automobiles.

4. What is meant by reformulated and oxygenated gasoline?

.

5. What i s meant by reversible fuel cell?

6. Mention the various methods of storing hydrogen.

7. What is meant by transesterif icat ion?

8. Why biodiesel mixed with conventional diesel?

9. How can be fermentation process defined?

10. What are the advantages and limitations of alcohols are engine fuel?

PART B (16 MARKS )

01. Discuss the operation of an LPG propelled Automobile with neat sketch. (16)

02. Explain the construction and working principle of Fuel cells, with simple

sketches. (16)

03. How bio diesel is produced? Explain and its usage in automobile. (16)

04. Explain the operation of Hydrogen fueled vehicle with neat sketch. (16)

05. Discuss in detail about different al ternate fuels for automotive engines

with respect to the following aspects :

(i) Emission

(ii) Cost

(iii) Reliability

(iv) Availability

(v) Engine modifications needed. (16)

06. i) What is fuel cell? What are the advantages of Fuel Cells? (4)

ii) Explain in detail about different types of Hybrid vehicle

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constructions with neat sketches. (12)

07. i) Explain the method of biodiesel production through transesterification process. (8)

ii) Discuss the alternative fuel suitable for compression ignition engine driven

automobiles. (8)

08. i) Briefly explain the methods of using natural gas as diesel engine fuel. (8)

ii) List out the different properties of hydrogen relevant to its use of I.C. Engines. (8)

09. i) Explain the series and parallel hybrid drive trains. (8)

ii) Discuss the drive system of an electric vehicle. (8)

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