start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 14, the reader should be able to: • • • Add and subtract decimal numbers Read a chart and graph Calculate percentages Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: chart decimal point • diagram • direct drive • drive gear • driven gear fractions • gear reduction • graph • overdrive percentage • scientific notation • variable Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 DECIMAL Decimals are commonly used by services The placement of the decimal point indicates the value of the number The naming of decimals includes tenths, hundredths, thousandths, and higher Decimals are used to represent fractions of a unit by using a dot called a decimal point to indicate that the number is a decimal Tenths A decimal with one number to the right of the decimal point indicates an accuracy of 1/10 or 0.1 For example, 0.7 is the same as 7/10 and is pronounced “seven tenths” or “zero point seven.” A decimal can also include numbers larger than zero, but has a resolution or accuracy measured in tenths, such as in 14.7 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Hundredth Decimals with two numbers to the right of the decimal point indicate an accuracy to 1/100 or 0.01 For example, 0.47 is pronounced “forty-seven hundredth” or “zero point four seven.” Thousandth A decimal with three numbers to the right of the decimal point indicates an accuracy to 1/1000 or 0.001 For example, 0.867 is pronounced “eight hundred sixty-seven thousandths” or “zero point eight six seven.” Adding and Subtracting Decimals When adding or subtracting decimals, the decimal point has to be aligned This ensures that the numbers are placed into the correct position of tenth, hundredth, and thousandth For example: 0.147 + 0.02 0.167 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 PERCENTAGE Percentage is the relationship of a value or number out of 100 Using money as an example, three quarters (25 cents each) equals 75 cents ($0.75) or 75% of a dollar ($1.00) Many examples are not that easy, for example, 70 is what percentage of 120? To determine the percentage, divide the first number (70) by the second number (120) 70 ÷ 120 = 0.58 To convert this number to a percentage, multiply the number by 100 or move the decimal point two places to the right (58) and then add a percentage symbol to indicate that the number is a percentage (58%) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SCIENTIFIC NOTATION Very large and very small decimal numbers are frequently expressed using scientific notation, which written as a number multiplied by the number of zeros to the right or left of the decimal point For example, 68,000 could be written as 6.8 × 104 , indicating the number shown has zeros plus the to the right of the decimal point Small numbers, such as 0.00068, would use a negative sign beside the number over the 10 to represent that the decimal point needs to be moved toward the left (6.8 × 10-4) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 ADDING AND SUBTRACTING Techs are often required to add or subtract measurements when working on vehicles For example, adding and subtracting is needed to select shims (thin pieces of steel) for adjusting valve clearance or differential preload measurements For example, if the valve clearance specification is 0.012 in and the clearance is actually 0.016 in., and the shim that is in place between the camshaft lobe and the valve bucket is 0.080 in thick, what size (thickness) of shim needs to be installed to achieve the correct valve clearance? Solution: The shim thickness of 0.080 in results in a valve clearance of 0.016 in The specification requires that the shim needs to be thicker to reduce the valve clearance Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 14–1 Valve clearance allows the metal parts to expand and maintain proper operation, both when the engine is cold or at normal operating temperature (a) Adjustment is achieved by turning the adjusting screw (b) Adjustment is achieved by changing the thickness of the adjusting shim Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FRACTIONS Fractions, such as 1/2, 1/4, or 5/8 are commonly found in specifications for hose inside diameter measurements A tape measure or machinists rule can be used to measure the fitting or the original part Sometimes, fractions need to be converted to decimal units if the replacement parts are offered by that measurement method When comparing fractions to decimal units, think about the number of cents in a dollar 1/2 dollar 50 cents - 1/4 (quarter) 25 cents 1/10 (dime) 10 cents - 1/20 (nickel) cents Other fractions, such as 3/8, 5/8, and 5/16 are harder to determine If a chart is not available, divide the bottom number, called the denominator into the top number, called the numerator Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 10 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 MULTIPLYING AND DIVIDING Multiplying by a service tech is usually done to determine gear ratios and to determine the total of many of the same items For example, final overall gear ratio is determined by multiplying the transmission gear ratio by the final drive ratio and is covered later in this chapter Dividing is commonly done when calculating total resistance of many resistances connected in parallel In this situation, the value of the resistance is divided by the number of equal resistances For example, if four bulbs with a resistance of 0.4 ohm were connected in parallel, the total resistance would be just 0.1 ohm (0.4 ÷ = 0.1) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 11 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 MATHEMATICAL FORMULAS A formula uses letters to represent values or measurements and indicates how they are to be acted upon To use a formula, the tech needs to replace letters with the actual numbers and perform the indicated math functions For example, a formula to determine engine speed in revolutions per minute (RPM) is represented by the following formula: This is used to determine the speed of the engine compared to the gear ratio and tire size Wheel and tire sizes are changed at timed and knowing this is helpful Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 12 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 FUEL ECONOMY CALCULATOR Step #1 Fill the tank until the nozzle clicks off Step #2 Drive a reasonable distance Example—220 miles Step #3 Fill the fuel tank and record the number of gallons used For this example, exactly 10.0 gallons Step #4 Calculate fuel economy—MPG Miles driven divided by the number of gallons used MPG = 220 divided by 10.0 = 22.0 miles per gallon NOTE: Try to use the same station and pump, if possible, to achieve the most accurate results Outside the US fuel economy is measured in liters of fuel needed to travel 100 kilometers (62 miles), abbreviated L/100 km See the metric fuel chart on Page 106 of your textbook Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 13 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 GEAR RATIOS When one gear turns another, the speed the two gears turn in relation to each other is the gear ratio Gear ratio is expressed as the number of rotations the drive gear must make in order to rotate the driven gear through one revolution To obtain a gear ratio, divide the number of teeth on the driven gear by the number of teeth on the drive gear Gear ratios, which are expressed relative to the number one, fall into three categories: Direct drive Gear reduction Overdrive Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 14 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Direct Drive If two meshed gears are the same size and have the same number of teeth, they will turn at the same speed Since the drive gear turns once for each revolution of the driven gear, the gear ratio is 1:1 and is called direct drive When a transmission is in direct drive, the engine and transmission turn at the same speed Gear Reduction If one gear drives a second gear that has three times the number of teeth, the smaller drive gear must travel three complete revolutions in order to drive the larger gear through one rotation Figure 14–2 The drive gear is attached or is closer to the power source and rotates or drives the driven gear Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 15 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Gear Reduction (cont.) Divide the number of teeth on the driven gear by the number of teeth on the drive gear, the answer is a 3:1 gear ratio (pronounced three to one) This type of gear arrangement, where driven gear speed is slower than drive gear speed, provides gear reduction Gear reduction may also be called underdrive as drive speed is less than, or under, driven speed It is used for the lower gears in a transmission First gear in a transmission is called “low” gear because output speed, not gear ratio, is low Low gears have numerically high gear ratios A 3:1 gear ratio is a lower gear than those with a 2:1 or 1:1 gear ratio These three ratios taken in order represent a typical upshift pattern from low gear (3:1), to second gear (2:1), to drive gear (1:1) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 16 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Overdrive The opposite of gear reduction condition is overdrive and occurs when a driven gear turns faster than its drive gear As shown here, the driven gear turns three times for each turn of the drive gear The driven gear is said to over-drive the drive gear For this example, the gear ratio is 0.33:1 Overdrive ratios of 0.65:1 and 0.70:1 are typical of those used in automotive applications Figure 14–3 If the driven gear is rotating faster than the drive gear, it is called an overdrive ratio NOTE: Ratios always end in with a colon between The first number is less than if it is an overdrive ratio and greater than if it is a gear reduction ratio Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 17 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 GRAPHS, CHARTS AND DIAGRAMS Graph Reading A graph is a visual display of information, used in auto service to illustrate trends or specs along with some other variable A variable is a measurement that changes, such as engine speed or time Graphs displays two variables One changes from left to right on the horizontal, or X axis The other displays on the Y or vertical axis A graph is created by making series of dots at various locations and connecting the dots with a line Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 18 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Interpreting a Graph To interpret a graph, select point along the horizontal (X) axis, then look directly above the point where the line appears Mark this spot and look directly to the left along the vertical (Y) axis to see the value represented by the points on the graph Figure 14–4 A graph showing horsepower and torque Notice that the curves cross at 5252 RPM or a little bit to the right of the 50, which is expressed in hundreds times 10 (thousands) of RPM Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 19 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Chart Reading A chart is used to represent data, such as numbers or specifications, along with another variable, such as model or year of vehicle A chart is very useful for showing many different specifications or other facts in an easy-to-read format The next slide displays an example of a specifications chart, which shows the transmission parts listed along the horizontal axis (X axis) and gear of the automatic transmission along the vertical or Y axis Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 20 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Interpreting a Chart A chart can look complicated but if studied, is easy to interpret Look along the horizontal or vertical axis for information such as model year of the vehicle Then look directly above the model year to determine the specs for that year Figure 14–5 A typical chart showing what is applied in what gear in an automatic transmission Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 21 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Diagram Reading A diagram is a graphic design that explains or shows the arrangement of parts Diagrams are commonly used in the auto service industry to show how a component is assembled and in which order the parts are placed together Figure 14–6 An exploded view showing how the thermostat is placed in the engine Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 22 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Interpreting a Diagram A diagram shows the relationship of many parts Lines are used to show the centerline of the part and the identity of the part is often shown as a number or letter A separate chart or area of the diagram needs to be looked at to determine the name of the part Diagrams are most helpful when disassembling or assembling a component, such as a transmission For best results, use electronic information and print out the diagram so it can be written on and can be thrown away when the repair has been completed This process also helps prevent getting grease on the pages of a service manual Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 23 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY Decimals are used in many automotive applications and specifications Adding and subtracting decimal numbers are needed for many automotive service procedures A formula is used to determine the volume of something if other values are known A gear ratio is determined by dividing the number of teeth on the driven gear by the number of teeth on the drive gear Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 24 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 25 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458