Engine Operation and Theory

How far will an engine with a 1 million mile (1.6 million km) B-50 bearing life travel before the bearings are half worn?

1 million miles (1.6 million km)

Which of the following factors best accounts for a diesel engine's high thermal efficiency?

A high compression ratio

Which of the following should be done to correct insufficient liner protrusion?

Add shims to the liner counterbore

Technician A says that a diesel engine's high torque output is due to turbocharging. Technician B says a diesel engine's high torque output is due to its higher compression ratio. Who is correct?

Both Technician A and Technician B

Technician A says that diesel engines with high compression ratios produce more power, mix fuel and air better, and burn less fuel. Technician B says engines with high compression ratios need heavier, high-torque starting systems, more cylinder head bolts, and better sealing head gaskets. Who is correct?

Both Technician A and Technician B

Technician A says that long valve overlap periods help keep the exhaust valves and piston crowns cool. Technician B says that longer valve overlap helps fill the cylinder with more air, especially when the engine is turbocharged. Who is correct?

Both Technician A and Technician B

What type of ignition system does a diesel engine use to ignite fuel?

Compression

Which reason best explains why diesel engines typically operate three to five times longer than gasoline-fueled engines before wearing out?

Diesel engines operate at lower rpm.

Which of the following statements is true?

Diesel engines use substantially less fuel to produce the same power as a gasoline-fueled engine.

Which type of crankshaft hardening technique will result in the deepest amount of hardening?

Induction hardening

In a four-stroke internal combustion engine, during which stroke does air charge the cylinder?

Intake

Which position are the engine valves in during compression stroke?

Intake and exhaust valves are both closed

Which of the following engine configurations will result in the slowest piston speeds at the top and bottom of each piston stroke?

Long stroke engine

Technician A and B are discussing how to determine the correct direction of rotation when adjusting the valves and injectors of an inline six cylinder engine. Both valves are closed on Cylinder 1 as the engine turns past TDC. The next valve to open is the intake valve. Technician A says the engine is being turned correctly. Technician B says you cannot tell whether the engine is being turned correctly by looking at valve opening. Who is correct?

Neither Technician A nor Technician B

Technician A says diesel engines only make up 5% of the vehicles on the road, which is the reason they produce less pollution. Technician B says diesels burn less fuel, which explains why they produce less air pollution. Who is correct?

Neither Technician A nor Technician B

Technician A says increasing an engine's compression ratio will produce better fuel economy but less power output. Technician B says increasing an engine's compression ratio produces more power but increases fuel consumption. Who is correct?

Neither Technician A nor Technician B

Consider an engine with a high torque rise. Technician A says that it is best used in line haul highway tractors and can use a transmission with fewer gear steps. Technician B says that it is best used for vocational applications such as dump trucks, city buses, and delivery vehicles and needs to use a transmission with more gear steps. Who is correct?

Technician A

Technician A says that diesel engines are reciprocating engines. Technician B says that the use of a flywheel classifies any engine a rotary engine. Who is correct?

Technician A

Technician A says that diesel engines can produce more power because air and fuel are not mixed during the intake stroke. Technician B says that diesel engines produce more power because they use excess air to burn fuel. Who is correct?

Technician A

Technician A says that diesel engines supply only enough air to completely burn all the fuel in the combustion chamber. Technician B says that diesel engines supply excess air to the combustion chamber to completely burn all the fuel in the combustion chamber. Who is correct?

Technician A

Technician A says that when using Plastigauge, Plastigauge that becomes wider indicates a smaller oil clearance between a crankshaft and main bearing. Technician B says the Plastigauge will become narrower when bearing oil clearances are smaller. Who is correct?

Technician A

While examining a heavy, flat steel plate bolted to the oil pan rails and main bearing caps, Technician A suggests it is used to stiffen the crankcase to reduce torsional twisting. Technician B says the plate is used to prevent oil from splashing up onto the cylinder walls and causing high oil consumption. Who is correct?

Technician A

While installing new rod bearing inserts, the shells protruded very slightly above the margin of the bearing cap. Technician A says this is normal. Technician B says that wrong bearings are producing this result. Who is correct?

Technician A

Technician A says that a diesel's high torque output is due to its slow speed characteristics and short crankshaft throws. Technician B says that a diesel's high torque output is created when more air and fuel are added to the cylinder. Who is correct?

Technician B

Technician A says that an engine's rated horsepower is determined by measuring power output on a dynamometer. Technician B says that rated horsepower information is on the engine emission decal. Who is correct?

Technician B

Technician A says that biodiesel fuel is too expensive to purchase and will soon become unavailable because there is no interest in using it. Technician B says more biodiesel will be used in the near future because there are laws requiring increased production and blending of biodiesel with regular diesel. Who is correct?

Technician B

Technician A says that engine torque output is varied by changing engine speed. Technician B says that more torque is produced by injecting and burning more fuel. Who is correct?

Technician B

After moving through one crankshaft rotation, how many cylinders would have a power stroke in a four-stroke, Otto cycle, six-cylinder engine?

Three

Which of the following is the purpose of bolster bolts or tie bolts?

To increase engine block rigidity and strength

Which of the following sets of variables is required to measure horsepower?

Torque, time, rpm

Consider a six cylinder engine with 90° of total valve overlap. Cylinder 1 is at TDC at the end of its compression stroke. The firing order is 1-5-3-6-2-4. Which of the following observations can be made?

Two tight rocker levers on Cylinder 6

Rudolf Diesel developed the idea for a more efficient engine using:

a CI combustion system.

During the last few years, emissions from heavy-duty diesel trucks and buses have:

been significantly reduced.

The presence of cavitation on a replaceable cylinder liner is most likely caused by:

liner vibration.

Carbon dioxide is:

regulated by fuel economy standards.

The stroke length of an engine can only be changed by changing:

the length of the crankshaft throw.

Detroit Diesel two-stroke engines operate more smoothly than four-stroke cycle engines because:

there are twice as many power strokes per revolution as a four-stroke cycle.

Down speeding is:

using low axle gear ratios to reduce engine speed.