CDX Chapter 8 Exam

At which of the following compression ratios does the efficiency of an engine begin to diminish with increasing compression? - ANSWER-23:1 Technician A says that IDI engines need to use multi-orifice nozzles to mix air and fuel well. Technician B says that only DI combustion chambers use multi-orifice nozzles. Who is correct? - ANSWER-Technician B A centrally located fuel injector in a diesel engine is most likely to have how many valves per cylinder? - ANSWER-Four The average compression ratio used by on-highway DI engines is: - ANSWER-16:1 Technician A says that a diesel engine's higher compression ratio helps mix air and fuel better. Technician B says that higher compression ratio engines generally require more cylinder head bolts. Who is correct? - ANSWER-Both Technician A and Technician B Technician A says pilot injection helps an engine to operate quietly by shortening the ignition delay period. Technician B says high-cetane fuel reduces combustion noise associated with ignition delay. Who is correct? - ANSWER-Both Technician A and Technician B Technician A says that after an engine starts and warms up, white smoke indicates only an engine misfire condition. Technician B says that white smoke during cranking indicates coolant is leaking into a cylinder. Who is correct? - ANSWER-Neither Technician A nor Technician B Technician A says that glow plugs are needed in some diesels to heat the air inside the cylinder to enable an engine to start. Technician B says that glow plugs are needed by some engines to vaporize fuel to get an engine to start. Who is correct? - ANSWER-Technician B Which of the following is an advantage of indirect injection combustion chambers? - ANSWER-They enable high-speed engine operation. Which of the following reasons would account for the "knocking" sound in a diesel engine? - ANSWER-Ignition delay Technician A says that diesel engines have greater torsional vibration because they have lean-burn combustion systems. Technician B says torsional vibration is not a problem when gear trains are moved to the rear of an engine. Who is correct? - ANSWER-Neither Technician A nor Technician B