The document provides information about turbocharging and supercharging engines. It explains that turbochargers and superchargers work by forcing more air into the engine cylinders to increase power. A turbocharger uses exhaust gases to power a turbine, which drives an air compressor, while a supercharger is driven directly by the engine. The document describes the different types of superchargers and turbochargers, and discusses how boost pressure is controlled and maintenance procedures for forced induction systems.

1. TURBOCHARGING AND SUPERCHARGING 25

2. Objectives The student should be able to: Prepare for ASE Engine Performance (A8) certification test content area “C” (Fuel, Air Induction, and Exhaust Systems Diagnosis and Repair). Explain the difference between a turbocharger and a supercharger.

3. Objectives The student should be able to: Describe how the boost levels are controlled. Discuss maintenance procedures for turbochargers and superchargers.

4. INTRODUCTION

5. Introduction Airflow Requirements Naturally aspirated engines use atmospheric pressure to push air-fuel mixture into combustion chamber Mixture is compressed to increase force of burning, expanding gases

6. Introduction Airflow Requirements The greater the compression, the greater the engine power Four-stroke engines can only take in so much air

7. Introduction Airflow Requirements Engine airflow requirements determined by Engine displacement Engine revolutions per minute (RPM) Volumetric efficiency

8. Introduction Volumetric Efficiency Measurement compares actual volume of air-gas mixture with theoretical maximum volume

9. Introduction Volumetric Efficiency Volumetric efficiency decreases as engine speed increases Average engine never reaches 100% volumetric efficiency New engine is about 85% efficient

10. Introduction Volumetric Efficiency Race engine is about 95% efficient Turbochargers or supercharges allow engines to exceed 100%

11. Figure 25-1 A supercharger on a Ford V-8.

12. Figure 25-2 A turbocharger on a Toyota engine.

13. FORCED INDUCTION PRINCIPLES

14. Forced Induction Principles Purpose and Function Force an air-fuel charge produces when ignited is a function of charge density Charge density is amount of air-fuel charge introduced into cylinders

15. Figure 25-3 The more air and fuel that can be packed in a cylinder, the greater the density of the air-fuel charge.

16. Forced Induction Principles Purpose and Function The greater the density of an air-fuel charge the greater the force produced

17. Forced Induction Principles Purpose and Function Engine using atmospheric pressure for intake charge is naturally aspirated

18. Forced Induction Principles Purpose and Function A better way to increase air density is with air pump such as turbocharger or supercharger

19. Forced Induction Principles Purpose and Function Pumping air into cylinder provides combustion chamber with increased air pressure known as boost

20. Forced Induction Principles Purpose and Function Boost can be measured several ways Pounds per square inch (PSI)

21. Forced Induction Principles Purpose and Function Boost can be measured several ways Atmospheres (ATM) (1 atmosphere is 14.7 PSI)

22. Forced Induction Principles Purpose and Function Boost can be measured several ways Bars (1 bar is 14.7 PSI)

23. Forced Induction Principles Purpose and Function Boost increases air density thereby increasing friction that heats air Increased temperature decreases air density

24. Forced Induction Principles Purpose and Function Increased pressure doesn’t always produce greater air density

25. Forced Induction Principles Forced Induction Principles Forced induction systems use air pump to pack denser air-fuel charge into cylinders The weight of the air-fuel charge is higher

26. Forced Induction Principles Forced Induction Principles Forced induction systems use air pump to pack denser air-fuel charge into cylinders Power is increased because it is related to weight of air-fuel charge consumed within given time period

27. Forced Induction Principles Forced Induction Principles Pumping air into intake system under pressure allows more air to enter intake port before valve closes

28. Forced Induction Principles Forced Induction Principles Increased airflow allows more fuel to be added with same air-fuel ratio Denser air-fuel charge allows greater potential energy from combustion

29. Forced Induction Principles Forced Induction Principles Advantages of Supercharging Increases air-fuel charge density for high-compression pressure when power is needed

30. Forced Induction Principles Forced Induction Principles Advantages of Supercharging Engine runs on lower pressures when additional power is not needed

31. Forced Induction Principles Forced Induction Principles Advantages of Supercharging Pumped air pushes remaining exhaust from combustion chamber

32. Forced Induction Principles Forced Induction Principles Advantages of Supercharging Forced airflow and removal of exhaust gases lower temperature of cylinder head pistons and extends life of engine

33. Forced Induction Principles Forced Induction Principles Supercharger or turbocharger pressurization can be measured like atmospheric pressure

34. Forced Induction Principles Forced Induction Principles Atmospheric pressure drops with increased altitude Boost pressure remains the same regardless of altitude

35. Figure 25-4 Atmospheric pressure decreases with increases in altitude.

36. Forced Induction Principles Boost and Compression Ratios Boost increases amount of air drawn into cylinder during intake stroke The higher the boost pressure, the greater the compression ratio

37. Forced Induction Principles Boost and Compression Ratios Higher compression ratio requires superchargers and turbochargers to use the following: Forged pistons

38. Forced Induction Principles Boost and Compression Ratios Higher compression ratio requires superchargers and turbochargers to use the following: Stronger than normal connecting rods

39. Forced Induction Principles Boost and Compression Ratios Higher compression ratio requires superchargers and turbochargers to use the following: Piston oil squirters to control temperatures

40. Forced Induction Principles Boost and Compression Ratios Higher compression ratio requires superchargers and turbochargers to use the following: Lower compression ratio compared to naturally aspirated engines

41. Chart 25-1 The effective compression ratio compared to the boost pressure.

42. SUPERCHARGERS

43. Superchargers Introduction Supercharger is engine-driven air pump Boosts engine torque and power

44. Superchargers Introduction Provides instantaneous power increase Requires horsepower to operate

45. Superchargers Introduction Is not as efficient as a turbocharger Supercharger pumps air in direct relation to engine speed

46. Superchargers Types of Superchargers Roots Type Named for Philander and Francis Roots who patented supercharger in 1860

47. Superchargers Types of Superchargers Roots Type Patented as water pump for mines

48. Superchargers Types of Superchargers Roots Type Changed to pump air

49. Superchargers Types of Superchargers Roots Type Used on two-stroke-cycle Detroit diesel engines and other supercharged engines

50. Superchargers Types of Superchargers Roots Type Called positive displacement design: all air that enters Roots supercharger is forced through the unit

51. Figure 25-5 A roots-type supercharger uses two lobes to force the air around the outside of the housing and into the intake manifold.

52. Superchargers Types of Superchargers Centrifugal Supercharger Similar to turbocharger but mechanically driven by engine instead of being powered by hot exhaust gases

53. Superchargers Types of Superchargers Centrifugal Supercharger Not a positive displacement pump

54. Superchargers Types of Superchargers Centrifugal Supercharger Air enters centrifugal supercharger housing in the center and exits at the edges at a higher rate of speed

55. Superchargers Types of Superchargers Centrifugal Supercharger Speed of blades is higher than engine speed

56. Superchargers Supercharger Boost Control Many factory installed superchargers have a bypass valve that allows air to bypass the supercharger

57. Figure 25-6 The bypass actuator opens the bypass valve to control boost pressure.

58. Superchargers Supercharger Boost Control Airflow is directed around supercharger under these conditions Boost pressure indicates intake manifold pressure is reaching boost levels

59. Superchargers Supercharger Boost Control Airflow is directed around supercharger under these conditions Excessive pressure builds up during deceleration

60. Superchargers Supercharger Boost Control Airflow is directed around supercharger under these conditions Reverse gear is selected

61. Superchargers Supercharger Service Usually lubricated with synthetic engine oil Oil level should be checked and oil changed as specified by manufacturer

62. Superchargers Supercharger Service Drive belt should be inspected and replaced as necessary Air filter should be replaced regularly

63. Superchargers Supercharger Service Service information should be used to service separate cooling system on many superchargers

64. Figure 25-7 A Ford supercharger cutaway display showing the roots-type blower and air charge cooler (intercooler). The air charge cooler is used to reduce the temperature of the compressed air before it enters the engine to increase the air charge density.

65. TURBOCHARGERS

66. Turbochargers Introduction Major disadvantage of supercharger: it takes engine power to drive it Mechanical supercharger can take up to 20% of engine power

67. Turbochargers Introduction Turbocharger uses heat from exhaust to power turbine wheel About half of heat energy in fuel goes out exhaust system

68. Turbochargers Introduction Another 25% is lost through radiator cooling Only 25% is converted to mechanical power

69. Turbochargers Introduction A mechanically driven pump uses some of the mechanical power Turbocharger gets energy from exhaust gases

70. Figure 25-8 A turbocharger uses some of the heat energy that would normally be wasted.

71. Turbochargers Operation Turbocharger turbine looks like centrifugal pump for supercharging Hot exhaust gases flow from combustion chamber to turbine wheel

72. Turbochargers Operation Gases expand as they leave engine The expansion of hot gases turn turbine wheel’s blades

73. Turbochargers Operation Turbocharger has two chambers connected by center housing The two chambers contain turbine wheel and impeller (compressor) wheel connected by a shaft

74. Figure 25-9 A turbine wheel is turned by the expanding exhaust gases.

75. Turbochargers Operation Turbocharger must be positioned as close as possible to exhaust manifold Hot air passes into turbocharger with minimal heat loss

76. Turbochargers Operation The exhaust gas rotates the turbine blades Turbine wheel and compressor wheel on same shaft and turn at same speed

77. Turbochargers Operation Compressor wheel draws air in through central inlet Centrifugal force pumps it through outlet at edge of housing

78. Turbochargers Operation Pair of bearings in center housing supports turbine and compressor wheel shaft and is lubricated by engine oil

79. Figure 25-10 The exhaust drives the turbine wheel on the left which is connected to the impeller wheel on the right through a shaft. The bushings that support the shaft are lubricated with engine oil under pressure.

80. Turbochargers Operation Turbine and compressor wheels operate with extremely close clearances to minimize leakage

81. Turbochargers Operation Leakage around turbine blades causes dissipation of heat energy Leakage around compressor blades reduces full boost pressure

82. Turbochargers Turbocharger Operation When engine is started, exhaust heat and pressure are low Turbocharger runs at low speed (about 1000 RPM)

83. Turbochargers Turbocharger Operation Engine works like naturally aspirated engine As engine speed and load increase, exhaust heat and flow increase

84. Turbochargers Turbocharger Operation Turbine and compressor wheels accelerate as heat energy increases At full engine power, turbocharger rotates between 100,000 and 150,000 RPM

85. Figure 25-11 Engine oil is fed to the center of the turbocharger to lubricate the bushings and returns to the oil pan through a return line.

86. Turbochargers Turbocharger Operation Engine deceleration from full power to idle takes a second or two because of friction, pumping resistance, and drivetrain load

87. Turbochargers Turbocharger Operation Turbocharger has no load Turbocharger takes a minute or more to slow to idle

88. Turbochargers Turbocharger Operation If engine is turned off, lubrication flow to turbocharger stops Oil in center housing reaches extreme heat and can coke or oxidize

89. Turbochargers Turbocharger Operation Coked oil can clog passages and reduce turbocharger life High rotating speed and close clearance of turbine and compressor require critical bearing clearances

90. Turbochargers Turbocharger Operation Bearings must keep radial clearances of 0.003 to 0.006 in. (0.08 to 0.15mm) Axial clearance must be maintained at 0.001 to 0.003 in. (0.025 to 0.08 mm)

91. Turbochargers Turbocharger Operation To avoid problems with turbocharger Turbochargers need constant lubrication with clean oil; frequent oil changes are called for

92. Turbochargers Turbocharger Operation To avoid problems with turbocharger Dirt and other contaminants must be kept out of intake and exhaust housing

93. Turbochargers Turbocharger Operation To avoid problems with turbocharger When basic engine bearing has been damaged, turbocharger must be flushed with engine oil

94. Turbochargers Turbocharger Operation To avoid problems with turbocharger If turbocharger is damaged, engine oil must be drained and flushed and oil filter replaced

95. Turbochargers Turbocharger Operation Late-model turbochargers have liquid-cooled center bearings Engine coolant is circulated through center housing

96. Turbochargers Turbocharger Size and Response Time Time lag exists between increase in engine speed and increase in turbocharger speed The delay is called turbo lag

97. Turbochargers Turbocharger Size and Response Time Unlike supercharger, turbocharger cannot supply adequate boost at low speed Response time related to size of turbine and compressor wheels

98. Turbochargers Turbocharger Size and Response Time Small wheels accelerate rapidly; large wheels slowly Small wheels may not have enough airflow capacity for engine

99. Turbochargers Turbocharger Size and Response Time Intake and exhaust breathing of engine must be matched to capabilities of turbocharger

100. BOOST CONTROL

101. Boost Control Purpose and Function Supercharged and turbocharged systems provide pressure greater than atmospheric pressure Increased pressure forces additional air into combustion chamber

102. Boost Control Purpose and Function Increased charge increases engine power Amount of boost is measured in pound per square inch (PSI), in inches of mercury (in. Hg), in bars, or in atmospheres

103. Boost Control Purpose and Function 1 atmosphere = 14.7 PSI 1 atmosphere = 29.50 in. Hg

104. Boost Control Purpose and Function 1 atmosphere = 1 bar 1 bar =14.7 PSI

105. Boost Control Boost Control Factors Factors to consider when increasing boost pressure As boost pressure increases, air temperature increases As air temperature increases, combustion temperature increases

106. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Power can be increased by cooling compressed air after leaving turbocharger

107. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Typical cooling device is intercooler

108. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Intercooler is similar to radiator: outside air passes through cooling pressurized heated air

109. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Intercooler located between turbocharger and intake manifold

110. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Some intercoolers use engine coolant

111. Figure 25-12 The unit on top of this Subaru that looks like a radiator is the intercooler, which cools the air after it has been compressed by the turbocharger.

112. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Increased combustion temperature and pressure must be limited to avoid engine damage

113. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Maximum exhaust gas temperature is 1,440°F (840°C)

114. Boost Control Boost Control Factors Factors to consider when increasing boost pressure Higher temperatures can damage turbocharger and engine

115. Boost Control Wastegate Turbochargers use exhaust gas to increase boost The increased boost increases exhaust gas which again increases boost

116. Boost Control Wastegate To prevent overboost and engine damage most turbocharger systems have a wastegate A wastegate is a bypass valve at exhaust inlet to turbine

117. Boost Control Wastegate A wastegate can route part of exhaust past the turbine to exhaust system With less exhaust, turbocharger slows

118. Boost Control Wastegate Wastegate is continuous process to control boost pressure Wastegate is a pressure control valve usually controlled by computer

119. Figure 25-13 A wastegate is used on many turbocharged engines to control maximum boost pressure. The wastegate is controlled by a computer-controlled valve.

120. Boost Control Relief Valves A relief valve controls intake side of turbocharger Relief valve vents pressurized air from connecting pipe between turbocharger outlet and throttle

121. Boost Control Relief Valves Relief valve functions when throttle is closed during boost If pressure is not released, turbocharger will lag when throttle is opened again

122. Boost Control Relief Valves Two basic types of relief valves Compressor by pass valve (CBV) is quieter and routes pressurized air to inlet for reuse

123. Boost Control Relief Valves Blow-off valve (BOV) --also called dump valve or vent valve--uses adjustable spring to close valve until release of throttle

124. Figure 25-14 A blow-off valve is used in some turbocharged systems to relieve boost pressure during deceleration.

125. Figure 25-15 A dual turbocharger system installed on a small block Chevrolet V-8 engine.

126. TURBOCHARGER FAILURES

127. Turbocharger Failures Symptoms of Failure Turbocharger failure results in drop in power To restore operation, turbocharger must be rebuilt, repaired, or replaced

128. Turbocharger Failures Symptoms of Failure Turbochargers cannot be removed from vehicle Bearing failure common cause of turbocharger failure

129. Turbocharger Failures Symptoms of Failure Another problem is excessive and continuous oil consumption Turbochargers use small rings to prevent exhaust from entering central bearing

130. Turbocharger Failures Symptoms of Failure Excessive oil consumption is usually caused by one of the following Plugged positive crankcase ventilation (PCV) system

131. Turbocharger Failures Symptoms of Failure Excessive oil consumption is usually caused by one of the following Clogged air filter, causing low-pressure area in inlet and drawing oil past turbo shaft rings

132. Turbocharger Failures Symptoms of Failure Excessive oil consumption is usually caused by one of the following Clogged oil return (drain) line from turbocharger to oil pan

133. Turbocharger Failures Preventing Turbocharger Failures Regular oil changes (synthetic oil is best) Regular air filter replacement intervals Recommended inspections and services

134. NITROUS OXIDE

135. Nitrous Oxide Introduction Nitrous oxide is for racing or high performance only Relatively inexpensive way to get additional power

136. Nitrous Oxide Introduction Serious engine damage can occur if used incorrectly or excessively

137. Nitrous Oxide Principles Nitrous oxide (N 2 O) is colorless, nonflammable gas Discovered by British chemist Joseph Priestly

138. Nitrous Oxide Principles Causes light-headedness if breathed (known as laughing gas) Once used in dentistry to reduce pain Nitrous oxide is a manufactured gas

139. Nitrous Oxide Engine Power Adder Power adder is device or system added to engine, such as supercharger, turbocharger, or nitrous oxide to increase power

140. Nitrous Oxide Engine Power Adder Nitrous oxide injected into engine along with extra gasoline N 2 O adds extra oxygen for extra fuel

141. Nitrous Oxide Engine Power Adder NOTE: Nitrous oxide was used as power adder in World War II on some fighter aircraft. Having several hundred more horsepower for a short time saved many lives.

142. Nitrous Oxide Pressure and Temperature Requires about 11 lb of pressure per degree Fahrenheit to condense nitrous oxide gas into liquid nitrous oxide

143. Nitrous Oxide Pressure and Temperature To change N 2 O from liquid to gas, all that is needed is to lower its pressure below the pressure it takes to cause it to become a liquid.

144. Chart 25-2 Temperature/pressure relation for nitrous oxide: The higher the temperature, the higher the pressure.

145. Nitrous Oxide Pressure and Temperature Temperature affects pressure of N 2 O N 2 O is stored in pressurized container

146. Nitrous Oxide Pressure and Temperature Installed at angle so pickup tube is in the liquid Front or discharge end of bottle should be toward front of vehicle

147. Figure 25-16 Nitrous bottles have to be mounted at an angle to ensure that the pickup tube is in the liquid N 2 O.

148. Nitrous Oxide Wet and Dry System Two types of N 2 O systems Wet system involves additional fuel being injected

149. Nitrous Oxide Wet and Dry System Two types of N 2 O systems Identified by two nozzles; red supplying gasoline and blue supplying N 2 O

150. Nitrous Oxide Wet and Dry System Two types of N 2 O systems Dry system does not include gasoline

151. Nitrous Oxide Wet and Dry System Two types of N 2 O systems PCM can be commanded to provide more fuel when N 2 O is sprayed

152. Nitrous Oxide Engine Changes Needed for N 2 O If N 2 O is used to increase horsepower more than 50 hp, engine must be designed and built for greater heat and pressure

153. Nitrous Oxide Engine Changes Needed for N 2 O The following items should be considered for adding turbocharger, supercharger, or nitrous oxide Forged pistons to withstand increased pressure and temperature

154. Nitrous Oxide Engine Changes Needed for N 2 O The following items should be considered for adding turbocharger, supercharger, or nitrous oxide Cylinder-to-wall clearance increase to compensate for greater heat

155. Nitrous Oxide Engine Changes Needed for N 2 O The following items should be considered for adding turbocharger, supercharger, or nitrous oxide Forged crankshaft and connecting rods

156. Nitrous Oxide Engine Changes Needed for N 2 O Check instructions from N 2 O supplier for details and other changes

157. Nitrous Oxide Engine Changes Needed for N 2 O CAUTION: The use of nitrous oxide injection system can cause catastrophic engine damage. Always follow instructions that come with the kit and be sure all internal engine parts meet standard specified to help avoid severe engine damage.

158. Nitrous Oxide System Installation and Calibration Nitrous oxide systems usually purchased as kit Kit includes one or more sizes of nozzles calibrated to control flow of N 2 O

159. Nitrous Oxide System Installation and Calibration Sizes of nozzles are calibrated in horsepower gained by their use 50 hp 100 hp 150 hp

160. Nitrous Oxide System Installation and Calibration Installation of N 2 O kit includes on-off switch and switch on or near throttle Switch is activated only when throttle is fully opened (WOT)

161. TECH TIP Faster Moves More Air One of the high-performance measures that can be used to increase horsepower on a supercharged engine is to install a smaller diameter pulley. The smaller the pulley diameter, the faster the supercharger will rotate and the higher the potential boost pressure will be. BACK TO PRESENTATION The change will require a shorter belt, and the extra boost could cause serious engine damage.

162. TECH TIP Boost Is the Result of Restriction The boost pressure of a turbocharger (or supercharger) is commonly measured in pounds per square inch. If a cylinder head is restricted because of small valves and ports, the turbocharger will quickly provide boost. BACK TO PRESENTATION Boost results when the air being forced into the cylinder heads cannot flow into the cylinders fast enough and “piles up” in the intake manifold, increasing boost pressure. If an engine had large valves and ports, the turbocharger could provide a much greater amount of air into the engine at the same boost pressure as an identical engine with smaller valves and ports. Therefore, by increasing the size of the valves, a turbocharged or supercharged engine will be capable of producing much greater power.

163. TECH TIP If One Is Good, Two Are Better A turbocharger uses the exhaust from the engine to spin a turbine, which is connected to an impeller inside a turbocharger. This impeller then forces air into the engine under pressure, higher than is normally achieved without a turbocharger. The more air that can be forced into an engine, the greater the power potential. BACK TO PRESENTATION A V-type engine has two exhaust manifolds and so two small turbochargers can be used to help force greater quantities of air into an engine, as shown in FIGURE 25–15. Figure 25-15 A dual turbocharger system installed on a small block Chevrolet V-8 engine.

164. TECH TIP Increase Bottle Pressure To increase the pressure of the nitrous oxide in a bottle, an electrical warming blanket can be used, as seen in FIGURE 25–17. The higher the temperature, the higher the pressure and the greater the amount of N 2 O flow when energized. BACK TO PRESENTATION Figure 25-17 An electrical heating mat is installed on the bottle of nitrous oxide to increase the pressure of the gas inside.