Automobile Theories of Operation Chapter Seven Automobile Theories of Operation

Objectives Discuss theories of physics in designing and operating vehicles Discuss first two laws of thermodynamics and their application in an engine Define energy and the two types of energy

Objectives Discuss how pressure and vacuum help operate the engine Discuss Newton’s three Laws of Motion Define electricity, voltage, current, and resistance Discuss magnetism

Objectives Name types of electrical circuits Discuss use of hydraulics in vehicles Discuss other factors in designing and operating a vehicle Discuss horsepower and torque

Introduction Automobile is made up of eight major interactive systems Power to the vehicle and components Comfort and protect the passenger

Thermodynamics Study of using radiant heat to perform mechanical work First Law Energy cannot be created or destroyed

Thermodynamics Second Law In a perfect heat engine Heat produced would be completely converted to mechanical work

Energy and Work Energy is the capacity of matter to perform work through its motion or position Work is a unit of energy and may be measured in foot-pounds (ft-lbs.)

Pressure and Vacuum Pressure is amount of force used to hold a gas or liquid in place Atmospheric pressure can be used to achieve work in a vehicle or components

Pressure and Vacuum Vacuum is pressure below atmospheric pressure Automotive systems use these principles to operate

Newton’s Laws of Motion First Law An object at rest tends to stay at rest An object in motion tends to stay in motion Second Law A moving object will travel in a straight line and in one direction

Newton’s Laws of Motion Third Law For every action there is an equal and opposite reaction

Electrical Theory, Measuring, and Circuits George Simon Ohm One volt to push one ampere of current through one ohm of resistance Conductors Natural elements to move electrical current Only one electron in valence ring Best conductor is copper

Electrical Theory, Measuring, and Circuits Voltage Electrons are moved by voltage Voltage is Electromotive Force (EMF) Electron theory

Electrical Theory, Measuring, and Circuits Current Amount of moving electrons expressed in an understandable term Most automotive systems are relatively low amperage

Electrical Theory, Measuring, and Circuits Resistance Anything that uses voltage Nonconductive elements are resistant and classified as insulators Corrosion can cause resistance Unintentional resistance can disrupt circuit operation

Electrical Theory, Measuring, and Circuits Magnetism Created any time current is flowing Number of windings and how they are insulated from one another affects magnetic field strength Magnetic fields can be used to create electricity

Electrical Theory, Measuring, and Circuits Electrical Measurements Instruments are necessary to allow control of electricity Ohm’s Law can calculate whether a circuit is operating properly

Electrical Theory, Measuring, and Circuits Path electricity follows from negative to positive side Can work with a power source, conductor, and load

Electrical Theory, Measuring, and Circuits Series Circuits Provide one path for current to travel Defect in circuit will affect entire circuit Generally not used in automotive applications True series circuit is the starter circuit

Electrical Theory, Measuring, and Circuits Parallel Circuits Provide more than one path to ground Common in automotive applications One failed component will not affect entire circuit Typical circuit Exterior lighting

Electrical Theory, Measuring, and Circuits Series-Parallel Circuits Most common circuit in automotive applications Series portion controls parallel portion Typical circuit Headlamp circuit

Electrical Theory, Measuring, and Circuits Circuit Protection Protect circuits from overload situations Designed to protect other circuits and even the whole vehicle Fuses melt at preset amperage amounts Circuit breakers are similar to fuses, but can be reset instead of replaced

Electrical Theory, Measuring, and Circuits Circuit Defects Open Circuit is incomplete and current can’t flow Short-to-Ground Two conductors have worn through insulation Results in a switch turning on more than its designed circuit

Electrical Theory, Measuring, and Circuits Circuit Defects Short-to-Ground Unintentional connection between a feed conductor and ground

Electrical Service Information Wiring Diagram Paper- or computer-based diagrams Various circuits and devices Most show wire colors and wire sizes Newer systems may also have diagrams Component Locators List items and their locations in vehicle

Hydraulic Theory Pressure in a closed hydraulic circuit will be the same everywhere in the circuit Hydraulic circuits are similar to electrical circuits

Hydraulic Theory Three measures in hydraulic circuits Force, pressure, area Hydraulic fluids selected on type of system in use and work being performed

Vehicle Design Aerodynamics Study of how an object moves through air Can affect performance and fuel mileage

Vehicle Design Passenger Protection Seat belts and air bags are designed to protect the passenger in an accident Crumple zones have been added to absorb impact forces

Vehicle Design Materials Must be selected to provide specific performance in applications Gaskets must be able to work with different materials on either side

Vehicle Design Horsepower versus Torque Horsepower is speed Torque is pulling

Working Around Supplemental Restraint Systems (SRS) Caution must be exercised when working around SRS systems Disconnect power any time you are working around the system

Working Around Supplemental Restraint Systems (SRS) Never probe connectors with powered test lights Serious injury or death can result from neglecting safety precautions

Diagnostic Steps Six Steps to Follow Confirm customer’s complaint Collect vehicle data Collect vehicle TSB, recalls, or other information Test system Determine and complete repair Test repair

Summary Newton Laws Volts, ohms, and amperes are electrical measurements Measurements of hydraulics are force, area, and pressure Vehicle design is limited by available materials and technology