Chapter 10 Emission Control and Exhaust System Fundamentals 203 Copyright by Goodheart-Willcox Co., Inc. 3. How does limiting the surface area of the combustion chamber reduce HC emissions? 4. Explain how a lower compression ratio decreases NO X emissions. 5. Most cylinder-head designs have ____ valves per cylinder. (A) two (B) four (C) fi ve (D) Both A and B. 6. Describe how the PCV system reduces emissions. 7. Why are heated oxygen sensors used now instead of the older, nonheated sensors? 8. Describe how the basic evaporative emission control system operates. 9. What is the purpose of the air-injection system? 10. How does the EGR system reduce NO X emissions? 11. What is the purpose of the exhaust manifold? 12. Describe the function of the front section and the rear section of a three-way catalytic converter. 13. Th e catalytic converter on a diesel engine contains a trap to capture ____. 14. What causes backpressure in the exhaust system? 15. Briefl y describe an I/M program. ASE-Type Questions—Chapter 10 1. Technician A says that thermostats increase engine temperature to prevent NO X formation. Technician B says that thermostat operation is monitored to prevent overheating. Who is correct? (A) A only. (B) B only. (C) Both A and B. (D) Neither A nor B. 2. All of the following can cause ice formation at the throttle plate, except: (A) high humidity. (B) high engine temperature. (C) low outside air temperature. (D) low air pressure. 3. Th e main advantage of electronic engine controls is that they have allowed the practical use of ____. (A) fuel injection (B) catalytic converters (C) EGR valves (D) evaporative emission control systems 4. Technician A says that lowering the engine compression ratio allows the engine to run on diesel fuel. Technician B says that lowering the engine compression ratio lowers engine effi ciency. Who is correct? (A) A only. (B) B only. (C) Both A and B. (D) Neither A nor B. 5. Which of the following parts are only found on a diesel engine exhaust system? (A) resonator (B) heated O 2 sensor (C) two-stage converter (D) NO X sensor 6. Technician A says that the PCV system reduces pollution from the fuel tank. Technician B says that unburned fuel can accumulate in the crankcase and must be removed. Who is correct? (A) A only. (B) B only. (C) Both A and B. (D) Neither A nor B. 7. Th ermostatic air cleaners prevent all of the following problems, except: (A) overheating. (B) icing of the throttle valve. (C) hesitation when cold. (D) poor driveability during warm-up. 8. Technician A says that the evaporative emission control system reduces pollution from the exhaust system. Technician B says that the EGR valve does not operate at idle. Who is correct? (A) A only. (B) B only. (C) Both A and B. (D) Neither A nor B.