Chapter Seven Automobile Theories of Operation Objectives Discuss

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 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 • 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