Introduction to Automotive Technology

Introduction to Automotive Technology
CHAPTER 2 Introduction to Automotive Technology © GlowImages/Alamy Images

Introduction (1 of 2) Preparing to work in the automotive repair industry means learning and mastering a whole new vocabulary. You will also need to master the metric system. Knowing correct terminology and concepts will help you fit into your new work environment while you maintain, diagnose, and repair vehicles. 2

Introduction (2 of 2) This chapter will help you start the process of learning automotive technology as it relates to: Vehicle types Drive train layouts Engine configurations Axle arrangements 3

Body Designs (1 of 2) Vehicle bodies come in a variety of designs.
Design accommodates: Style Aesthetics Safety Constantly evolves © William Attard McCarthy/ShutterStock, Inc. © Rob Wilson/ShutterStock, Inc.

Body Designs (2 of 2) Strong marketing tool
Common types of body design cater to both passenger and light commercial use. Terms to describe body designs become part of common automotive language. Names can vary from country to country.

Sedan (1 of 2) Enclosed body
Maximum of four doors to passenger compartment © Maksim Toome/ShutterStock, Inc.

Sedan (2 of 2) Allows for storage in a trunk
Located in the rear of the vehicle Accessible from a trunk lid Traditionally has fixed roof

Coupe (1 of 2) Has just two doors
Traditionally has two standard-sized seats in front Possibly two smaller seats behind

Coupe (2 of 2) Available in fixed roof and convertible style
Equipped with a trunk for storage purposes © Rob Wilson/ShutterStock, Inc.

Hatchback Three-door and five-door design
Odd-numbered door is a hatch. Rear seats usually fold down to increase storage. Versatile vehicles © Maksim Toome/ShutterStock, Inc.

Convertible (1 of 2) Converts from an enclosed top to an open top
Roof that can be removed, retracted, or folded Mechanism driven by electronic motors that operate roof cover © Michael Shake/ShutterStock, Inc. © Maksim Toome/ShutterStock, Inc.

Convertible (2 of 2) Hardtop convertibles can be a series of folding steel or fiberglass panels. In other vehicles only a smaller section of the roof area is convertible. Traditionally the term roadster was applied to a vehicle with no permanent roof covering or side windows. Today that name is most often used to describe any convertible sports car.

Station Wagon (1 of 2) Has extended roof all the way to the rear of the vehicle Extra length in roof increases storage. In some cases, passenger capacity is increased. © Transtock Inc./Alamy Images

Station Wagon (2 of 2) Large rear door for easy access
Rear seats can usually be folded to increase storage even further. Usually has a fixed roof

Pick-up (1 of 2) Carries and tows cargo
Usually has heavier duty chassis components and suspension than a passenger car Traditionally only a single cab with two doors

Pick-up (2 of 2) Often, the four-door pick-up has reduced cargo-carrying space to accommodate extra seating in passenger cab. © Brad Sauter/ShutterStock, Inc.

Minivan (1 of 2) Generally lighter duty
Suspension systems like passenger cars Can be configured to maximize number of seats for passengers or cargo space © Alvey & Towers Picture Library/Alamy Images

Minivan (2 of 2) Fuel economy is substantially better than full-size vans.

Sport Utility Vehicle (SUV) (1 of 2)
Popular in United States because it can easily be used to carry out functions that otherwise require several different vehicles Acts like both a full-size van and a pick-up

Sport Utility Vehicle (SUV) (2 of 2)
Has a heavier-duty chassis so it can carry heavier loads Great for family outings © Maksim Toome/ShutterStock, Inc.

Vehicle Chassis (1 of 4) Underlying supporting structure on which components are mounted Traditional chassis gives the vehicle structural strength and platform to mount components

Vehicle Chassis (2 of 4) Originally chassis were made of wood.
Soon changed to an open steel ladder-frame structure Body-on-frame When a vehicle body is mounted on a rigid frame or chassis

Vehicle Chassis (3 of 4) Unibody design or single shell design
In the 1960s most manufacturers switched to a design that either partially or wholly integrated the bodywork into a single unit with the chassis. Constructed of large amount of steel sheet metal panels precisely formed in presses and spot-welded together into a structural unit

Vehicle Chassis (4 of 4) Unibody design or single shell design
First used in aircraft, spread to automobiles Became popular because less of a chassis component saved costs

Vehicle Closure Design (1 of 3)
A vehicle body contains many openings apart from the door. These openings have to be secured. May require remote switch or lever to be activated

In some cases, the driver pulls a lever and the access door is opened mechanically.

Other doors may use electric- or vacuum-operated solenoids to release latch. The driver pushes a switch. Sends a signal to the release mechanism Releases the door Some rear hatch doors have a hinged window incorporated. Engine compartment hoods usually have remote release lever.

Vehicle Operation Overview (1 of 15)
For a vehicle to operate, it requires a means of converting stored energy into a form of energy that can turn the wheels. Typically, stored energy is in the chemical form of gasoline or diesel fuel. Newer vehicles are using energy in other chemical forms: Natural Gas Alcohol Biodiesel Hydrogen Battery acid

Chemical energy can be converted into mechanical energy in two primary ways. Operation of an internal combustion engine Operation of an electric motor Take energy in chemical form and convert to mechanical energy by causing shaft to rotate The crankshaft or the armature

Shaft provides mechanical energy to move vehicle and power all other accessories. The combustion engine converts energy from fuel supply. Creates a combustible mixture The mixture is compressed by pistons and ignited by a spark plug in the engine cylinders.

When driver initiates starting process by turning ignition key to run (or using smart key): Power is supplied from battery to vehicle circuits. Fuel pump pressurizes fuel system in preparation for the engine to start.

When the key is moved to the crank position (or start button pressed): The starter motor is energized and cranks over the engine. As soon as the engine has started and is running: Ignition key is released from start position. Engine continues to run while ignition key is in run position.

Depressing the accelerator: Increases the amount of fuel and air entering the engine Increases the engine speed and power As the engine cranks: The engine management system monitors engine sensors.

The fuel mixture is ignited by ignition system. Causes hot gases to expand The expansion pushes each piston down into the cylinder. Causes the crankshaft to rotate

As the pistons continue moving up and down: They rotate the crankshaft, turning the flywheel or flex plate. In a manual transmission: Flywheel transmits engine output to transmission through clutch. In an automatic transmission: Flex plate transmits engine output through a torque converter.

Transmission allows for a number of different gear ratios. Matches the engine’s speed and power output to desired road speed The transmission allows vehicle to start at low speeds with high torque to the wheels. As gear ratios change, vehicle attains higher road speed with lower engine speed.

The vehicle’s driveshaft connects the output from transmission to wheels via axles through a final drive assembly that divides up the drive to the powered wheels.

Vehicle brakes are fitted to the wheels to provide a means of slowing down or stopping the vehicle and operate on the principles of hydraulic pressure. Fitted to each wheel Operated by a brake pedal Connected to a master brake cylinder fitted under hood

Master brake cylinder has a power booster fitted to it. The wheel brake units apply brake friction pads to metal discs or drums connected to the wheels. Creates friction to slow the wheels’ rotation The harder the driver pushes on the brake pedal, the harder the brakes are applied.

The suspension system connects the wheels to the chassis or vehicle body through various linkages, shock absorbers, and springs. The suspension system evens out road shocks caused by irregular road surface. Safely keeps tires in contact with road surface

The steering system makes the connection between the steering wheel and the road. The driver can point the vehicle in the intended direction of travel. Power steering systems provide assistance to the driver to turn the vehicle’s wheels.

The electrical system is interconnected to all of the other systems. Includes the battery Operating the electrical accessories when engine is not operating The battery is continually recharged

Drive Train Layouts (1 of 7)
The drive train encompasses the major assemblies that power the vehicle down the road.

The drive train includes: The engine Transmission/transaxle Differential Axles Wheels

Drive trains are designed in different layouts. The drive train layout differs in a pick-up than in a high-performance sports car. Differences in configuration between drive train’s major assemblies define the layout.

The drive train layout includes three main engine mounting positions: Front-engine Mid-engine Rear-engine

Drive train layouts accommodate four common drive wheel arrangements. Front-wheel drive (FWD) Rear-wheel drive (RWD) All-wheel drive (AWD) Four-wheel drive (4WD)

Drive train layout is defined by: Engine position Engine orientation Type of drive

Using the variations Front-engine, front-wheel drive Front-engine, rear-wheel drive Front-engine, all-wheel drive/4WD Rear-engine, rear-wheel drive Rear-engine, all-wheel drive Mid-engine, rear-wheel drive Mid-engine, all-wheel drive

Classifying Engines (1 of 2)
Engines are classified by: Type Cylinder arrangement Number of cylinders/rotors Total engine displacement in cubic inches or liters

Classifying Engines (2 of 2)
Two common types of engines Piston engine Rotary engine The majority of automotive engines are of the piston type.

Piston Engines (1 of 5) The way engine cylinders are arranged is called the engine configuration. Multicylinder internal combustion automotive engines are produced in four common configurations. In-line Horizontally opposed V VR and W

Piston Engines (2 of 5) Engineers design engines with tilted cylinder banks to reduce engine height. Tilting can be carried to an extreme.

Piston Engines (3 of 5) As number of cylinders increases, length of engine block and crankshaft can become a problem structurally and space-wise. In vehicle applications, the number of cylinders can vary usually up to 12.

Piston Engines (4 of 5) Some examples are: In-line 4 V8 Flat 6 W12

Piston Engines (5 of 5) Common angles between the banks of cylinders are: 180 degrees 90 degrees 60 degrees 15 degrees Angles vary due to the number of cylinders and manufacturer’s design considerations

In-line Engine (1 of 2) Cylinders arranged side by side in single row.
Can be found in 3-, 4-, 5-, and 6-cylinder configurations

In-line Engine (2 of 2) Can be mounted two ways in engine bay.
Longitudinally Transversely (sideways) Generally less complicated to design and manufacture As a general rule of thumb, in-line engines are easier to work on than the other cylinder arrangements.

Horizontally Opposed (1 of 2)
Sometimes referred to as “flat” engines Commonly found in 4- and 6-cylinder configurations Shorter lengthwise than a comparable in-line engine but wider than a V type

Horizontally Opposed (2 of 2)
Have two banks of cylinders 180 degrees apart On opposite sides of the crankshaft Useful design when there is little vertical space Only fitted longitudinally

V Engines (1 of 4) Have two banks of cylinders sitting side by side in a V arrangement Sharing a common crankshaft

V Engines (2 of 4) Compact design allows for twice the power output from a V engine as an in-line engine of the same length. V engines can typically be found in 6-, 8-, 10-, and 12-cylinder configurations. Angle of the V varies according to number of cylinders Natural angle found by dividing 720 degrees by number of cylinders

V Engines (3 of 4) The natural angle for:
V8 is 90 degrees V6 is 120 degrees V10 is 72 degrees V12 is 60 degrees Designing around the natural angle means the engine can have a shorter length.

V Engines (4 of 4) Some manufacturers vary angles due to convenience or design requirements. Varying away from the natural angle means the crankshaft must have one cylinder per crank throw.

VR and W Engines VR engines use a single bank of cylinders.
Cylinders are staggered at a shallow 15-degree V within the bank. W engine consists of two VR cylinder banks in a deeper V arrangement to each other.

Rotary Engines (1 of 3) Very powerful for their size
Do not use conventional pistons that slide back and forth inside a straight cylinder Use a triangular rotor that turns inside an oval-shaped housing

Rotary Engines (2 of 3) Three combustion events for each rotation of the rotor As rotor turns, it carries the air–fuel mixture around the chambers, created between the tips of the rotor and the chamber wall. The rotor compresses the air–fuel mixture. Spark plugs ignite mixture.

Rotary Engines (3 of 3) Don’t have intake and exhaust valves like traditional piston engines Have intake ports covered and uncovered by the rotating rotor in the chamber Rotary engines generally have more than one rotor; two is the most common. Design of the rotary engine provides a very compact power unit.

Transmission and Axle Configurations (1 of 3)
In most vehicles, the engine is bolted firmly to either a transmission or transaxle. © Gordan Milic/ShutterStock, Inc.

Transmits engine power to a driveshaft, final drive, differential gears, and driving axles Usually in front-engine, rear-wheel drive vehicles

Transaxle Self-contained unit with transmission, final drive gears, and differential located in one casing Usually on front-engine, front-wheel drive vehicles or rear-engine, rear wheel drive vehicles Can also be used on some sports cars with front-engine, rear-wheel drive Transaxle connected to engine by a driveshaft

Live and Dead Axles (1 of 4)
Vehicles can be described by number of axles and drive wheels. Each axle typically has one wheel on each end of the axle. Axles come in two configurations.

Live axle Use engine’s torque to turn wheels (drive the vehicle); at the same time support weight of vehicle Wheels and axles on a live axle are also called drive wheels and drive axles since they propel the vehicle.

Support weight of vehicle only while allowing the wheels to rotate freely on the axle Wheels on dead axles are not considered drive wheels since they support the vehicle’s weight.

Most light vehicles have only two axles. On commercial vehicles, the load carried on a single axle is limited by law. A heavy vehicle may have six wheels (three axles) to support vehicle. Only four wheels (two axles) actually drive it. This vehicle is called a 6 × 2. If lazy axle is changed to drive axle, it becomes a 6 × 4.

Location of Live Axles (1 of 5)
Location of live axle determines classification: Front-wheel drive Rear-wheel drive Mid-engine, rear-wheel drive All-wheel drive

Front-wheel drive Live axle is at front of vehicle. Front wheels pull vehicle along. A live front axle in front of vehicle gives it lighter bodyweight and increased interior room. The engine and transaxle are at the front and can be mounted transversely or longitudinally.

Rear-wheel drive Live axle is at rear of vehicle and pushes the vehicle. The engine in front spreads out weight of drive train assemblies throughout vehicle. Some rear-wheel drive vehicles have engine at rear and drive the wheels through a transaxle.

Mid-engine, rear-wheel drive Engine is located behind drive but in front of rear drive axle. This design locates weight of engine near the center of vehicle. Allows for a low hood profile, balanced distribution of weight, and good handling Commonly used in sports cars

All-wheel drive Both axles are live and all four wheels drive (4 × 4) vehicle. Driving all four wheels requires additional components and complexity. Most 4 × 4 vehicles are more expensive and less fuel efficient than similar 4 × 2 vehicles.

Torque (1 of 6) The twisting force applied to a shaft
Used to drive the vehicle down the road Developed in the engine when combustion of the air–fuel mixture causes high pressure to push the piston down the cylinder and apply a twisting force to the crankshaft

Torque (2 of 6) The torque in the crankshaft is then used to twist the gears in the transmission. Then used to twist the axles Then used to twist the wheels and tires, which drives the vehicle down the road

Torque (3 of 6) Also used by technicians when tightening bolts and nuts Torque in the Imperial system is measured by the foot-pound (ft-lb) and inch-pound (in-lb)

Torque (4 of 6) Torque designation
The measure of torque is based on the equivalent twisting force exerted by an amount of weight (mass) applied to a perpendicular lever of a given length.

Torque (5 of 6) These designations are used in measuring torque:
A foot-pound (ft-lb) is the twisting force applied to a shaft by a lever 1 foot long with a 1-pound mass on the end. An in-pound (in-lb) is the twisting force applied to a shaft by a lever 1 inch long with a 1-pound mass on the end.

Torque (6 of 6) These designations are used in measuring torque:
A newton meter (Nm) is the twisting force applied to a shaft by a lever 1 meter long with a force of 1 newton applied to the end of the lever. 1 N is equivalent to the force applied by a mass of 102 grams, or .102 kg.

Transmission and Final Drives (1 of 8)
A vehicle with a manual transmission uses a clutch to engage and disengage the engine from the transmission.

Engine torque transmitted through clutch to transmission or transaxle The transmission or transaxle contains set of gears that increase or decrease the torque. Drive from transmission is transmitted to rest of drive train.

A vehicle starting from rest needs a lot of torque; once it is moving, it can maintain speed with only a small amount of torque. A higher gear ratio can then be selected and engine speed reduced. A conventional vehicle with the engine at the front and driving wheels at the rear uses a driveshaft to transmit torque from the transmission to the final drive.

Final drive provides a final gear reduction to multiply the torque before applying it to drive axles.

On front-engine, rear-wheel drive vehicles: The driveshaft is fitted down the centerline of the vehicle. The final drive at the rear of vehicle changes direction of drive by 90 degrees from center of vehicle out to wheels via axles.

On front-engine, rear-wheel drive vehicles: Inside final drive, a differential gear set divides torque to axles and allows for difference in speed of each wheel when cornering. Axles transmit torque to the driving wheels.

In a rear-wheel drive vehicle: Axles can be solid or contain joints to allow for movement of suspension. For a transaxle-equipped vehicle: Each driveshaft has movable joints to allow for suspension and steering movement.

An automatic transmission or transaxle performs similar functions to a manual transmission or transaxle. Gear selection is automatically controlled either hydraulically or electronically. The automatic transmission uses a torque converter. Acts as a hydraulic coupling to transfer the drive from the engine to the transmission

Four-Wheel Drive (1 of 3) A four-wheel drive (4WD) vehicle can drive all four wheels and has: Driveshaft Final drive and differential gears Axles for both the front and rear axle assemblies

Four-Wheel Drive (2 of 3) Part-time 4WD
Transfer case locks driveshafts together and directs torque through them to both axles. When disengaged, the vehicle transfer case is coupled to one driveshaft only. When disengaged, most part-time 4WD vehicles drive the rear wheels.

Four-Wheel Drive (3 of 3) Constant 4WD (all-wheel drive)
Uses a third differential in transfer case to allow for difference in speed between front and rear wheels during cornering

All-Wheel Drive (1 of 6) Provides drive to all four wheels
Should not be confused with part-time four-wheel drive vehicles The all-wheel drive cannot normally be disconnected or deselected.

All-Wheel Drive (2 of 6) Can be used on hard pavement with drive to all wheels Transfer case employs a center differential unit that allows the front and rear axles to rotate at slightly different speeds.

All-Wheel Drive (3 of 6) There are various methods of splitting the drive between the front and rear wheels. Some transfer cases use an electronically controlled multiplate clutch. Others use a viscous coupling. Both allow a small difference in speed between front and rear axles when vehicle is turning. Do not allow any great difference in speed when one or more of the wheels lose traction

All-Wheel Drive (4 of 6) The driver can still temporarily lock the front and rear axles together by moving a separate lever as in a conventional 4WD or by moving the main gear selector. A differential lock Some full-time 4WD sedans use a front engine and transaxle, with a driveshaft connected to drive the rear wheels.

All-Wheel Drive (5 of 6) Regardless of the type of system fitted, the aim is the same: To provide drive to all four wheels constantly while vehicle is in motion The power is not necessarily split 50/50 between the front and rear wheels. Torque is usually split 60% to the front wheels and 40% to rear wheels.

All-Wheel Drive (6 of 6) Some vehicles incorporate sophisticated traction and torque control systems to maintain effective traction of wheels to the road under all driving conditions. These systems vary the torque split between the front and rear wheels.

Summary (1 of 14) Learning automotive terminology is essential to becoming an automotive technician. Vehicle body design types include sedan, station wagon, hatchback, convertible, coupe, van, minivan, pickup, and sport utility vehicle (SUV).

Summary (2 of 14) Sedans have enclosed bodies with maximum of four doors. Coupes only have two doors. Either design can have a fixed roof or convertible. The hatch of a hatchback lifts at the rear of the vehicle to provide luggage area access. Convertibles can convert from enclosed top to open top via retractable roof.

Summary (3 of 14) Station wagons have increased luggage capacity due to an extended roof. Pick-up trucks are designed to support greater loads than passenger cars. Minivans are lighter duty versions of full-size vans. SUVs can carry and/or tow moderately heavy loads.

Summary (4 of 14) A vehicle chassis is the steel structure that supports the engine, wheels, and transmission. The unibody vehicle design replaced the body-on-frame design, allowing for lighter-weight cars that could be manufactured more quickly.

Summary (5 of 14) Vehicle openings include: engine compartment hood, hatch and tailgate openings, fuel door, and battery access covers. Engine compartment hoods have remote release levers to prevent unauthorized access. Vehicles must convert stored chemical energy into active mechanical energy.

Summary (6 of 14) Stored energy sources include: gasoline, diesel fuel, natural gas, alcohol, biodiesel, hydrogen, and battery acid. Conversion of chemical energy occurs via internal combustion engine or operation of electric motor. The transmission changes gear ratios to match engine speed and output to desired road speed.

Summary (7 of 14) The suspension system uses shock absorbers, linkages, and springs to connect the wheels to the chassis. The electrical systems include the battery, power train control system, lighting system, accessory systems, safety systems, passenger comfort systems, and entertainment systems.

Summary (8 of 14) The drive train is comprised of the engine, transmission/transaxle, differential, axles, and wheels. Drive train layout can have a front-, mid-, or rear-mounted engine, which can be oriented longitudinally or transversely. The four common drive wheel arrangements are: front-wheel drive, rear-wheel drive, all-wheel drive, and four-wheel drive.

Summary (9 of 14) Engines are classified according to type, cylinder arrangement, number of cylinders/rotors, and total engine displacement. The two types of engines are piston (most common) and rotary. Piston engines are configured in one of four ways: in-line, horizontally opposed, V, or VR/W.

Summary (10 of 14) Multicylinder engines vary in the number of cylinders; examples include in-line, 4, V8, flat 6, and W12. In-line engines have a single row of side-by-side cylinders. Horizontally opposed engines separate two banks of cylinders by 180 degrees, on either side of the crankshaft.

Summary (11 of 14) V-engines have two rows of side-by-side cylinders that share a crankshaft. VR/W engines are narrower and shorter than other engines. Rotary engines use one or more triangular rotors. Axles can be live and use engine torque to turn the wheels or dead and support the weight of the vehicle.

Summary (12 of 14) Axle location determines the drive wheel arrangement. Torque is a twisting force that is applied to the crankshaft by movement of the pistons or to nuts and bolts by a technician’s wrench. Manual transmissions require a clutch to transmit torque and engage/disengage the engine from transmission.

Summary (13 of 14) A conventional vehicle uses a driveshaft to transmit torque from the transmission to the final drive. Automatic transmissions use a torque converter instead of a clutch. Four-wheel drive vehicles can switch from two-wheel to four-wheel drive by engaging the transfer case attached to the transmission.

Summary (14 of 14) All-wheel drive vehicles cannot be switched to two-wheel drive. All-wheel drive vehicles provide constant drive to all four wheels, with only a small difference in speed between front and rear axles when the vehicle is turning.

Credits Unless otherwise indicated, all photographs and illustrations are under copyright of Jones & Bartlett Learning.

Introduction to Automotive Technology

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