Deck 4: Engine Basics

Question 1

The four strokes of the diesel cycle take place over:

A) 90 degrees rotation
B) 180 degrees rotation
C) 360 degrees rotation
D) 720 degrees rotation

Answer 1

720 degrees rotation

Question 2

If an engine is described as square, which of the following would be true?

A) Flat configuration
B) Must be an in-line 4 or 6 cylinder
C) Must be a 90 degree V configuration
D) Bore and stroke dimensions are equal

Answer 2

Bore and stroke dimensions are equal

Question 3

Which of the following acronyms is used to describe an engine piston that is at the exact bottom of its travel?

A) TDC
B) BDC
C) ATDC
D) BTDC

Answer 3

BDC

Question 4

Which of the following does most to define the piston stroke dimension?

A) Crank throw dimension
B) Connecting rod length
C) Swept volume
D) Clearance volume

Question 5

Which of the following defines actual piston stroke?

A) Crank throw
B) Two times crank throw
C) Bore divided by stroke
D) Rod eye to rod journal dimension

Question 6

Which of the following correctly defines piston swept volume?

A) Cylinder volume with piston at BDC
B) Cylinder volume with piston at TDC
C) Volume displaced by piston through its stroke
D) Volume of the piston assembly

Question 7

Which of the following compression ratios would be typical of a current, turbocharged highway truck diesel engine?

A) 10:1
B) 14:1
C) 17:1
D) 24:1

Question 8

Which of the following is true of the term clearance volume?

A) Cylinder volume with piston at TDC
B) Cylinder volume with piston at BDC
C) Cylinder volume with piston removed
D) Volume of a pre-combustion chamber

Question 9

What is a typical compression pressure achieved in a current highway truck diesel engine?

A) 150 PSI
B) 350 PSI
C) 600 PSI
D) 1200 PSI

Question 10

What is another way of saying manifold boost?

A) turbo boost
B) indirect injected
C) direct injected
D) volumetric efficiency

Question 11

What term is used to describe the tendency of an object in motion, to want to stay in motion?

A) static friction
B) dynamic friction
C) kinetic energy
D) inertia

Question 12

What would be the highest thermal efficiency achievable in a current truck diesel engine?

A) 10%
B) 25%
C) 40%
D) 60%

Question 13

If a diesel engine has a thermal efficiency of 35%, what percentage of the heat energy of the fuel is discharged as rejected heat?

A) 35%
B) 65%
C) Half of 35%
D) Half of 65%

Question 14

What is another name for the power stroke in the engine cycle?

A) Compression stroke
B) Scavenging stroke
C) Gas blowdown
D) Expansion stroke

Question 15

If an engine is run for maximum mechanical efficiency, where should peak cylinder combustion pressure be achieved?

A) TDC
B) around 15 degrees ATDC
C) around 45 degrees ATDC
D) at 90 degrees ATDC

Question 16

When exactly does the gas blowdown phase occur?

A) when exhaust valve first opens
B) at BDC during the exhaust stroke
C) close to TDC on the exhaust stroke
D) during cylinder scavenging

Question 17

When does scavenging occur in the 4-stroke, diesel cycle?

A) throughout intake stroke
B) throughout exhaust stroke
C) valve overlap
D) inertial exhaust phase

Question 18

What is a typical compression ratio used on current spark-ignited, gasoline fueled engines with indirect injection?

A) 8:1
B) 11:1
C) 14:1
D) 16:1

Question 19

If an engine is described as naturally aspirated, which of the following should be true?

A) Constant geometry turbocharger is used
B) Variable geometry turbocharge is used
C) Roots blower is used
D) There is no manifold boost

Question 20

Which of the following terms is used to describe the overall breathing efficiency of an engine?

A) scavenging
B) thermal efficiency
C) volumetric efficiency
D) combustion efficiency

Question 21

Which of the following is another way of saying kinetic energy?

A) inertia
B) energy of motion
C) heat energy
D) thermal efficiency

Question 22

What do you do to convert cubic inches into liters?

A) multiply by 61
B) divide by 61
C) multiply by 5/8
D) divide by 10

Question 23

What do you do to convert liters into cubic inches?

A) multiply by 61
B) divide by 61
C) multiply by 5/8
D) multiply by 10

Question 24

A Cummins X-15 has a total engine displacement of 15 liters. Convert this into cubic inches:

A) 893 cubic inches
B) 915 cubic inches
C) 943 cubic inches
D) 997 cubic inches

Question 25

A Navistar A26 engine has a total displacement of 12.4 liters. Convert this into cubic inches:

A) 756 cubic inches
B) 828 cubic inches
C) 934 cubic inches
D) 1052 cubic inches

Question 26

Convert the specified displacement of a MaxxForce DT engine with a displacement of 466 cubic inches into liters:

A) 7.6 liters
B) 8.2 liters
C) 8.9 liters
D) 9.4 liters

Question 27

What is the term used to describe the relationship between the work performed by a piston during the compression stroke, and the work received by it during the power stroke?

A) brake horsepower (BHP)
B) torque gain
C) mean effective pressure (MEP)
D) constant volume cycle

Question 28

How many times does any one piston change direction during one complete diesel cycle?

A) two times
B) four times
C) six times
D) eight times

Question 29

What percentage of carbon is found in a typical highway diesel fuel?

A) 15%
B) 35%
C) 50%
D) 85%

Question 30

Technician A says that peak combustion pressures in modern diesel engines may be five times greater than the compression pressure in some modes of operation. Technician B says that while a diesel engine is idling, compression pressures may exceed combustion pressures. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 31

Technician A says that turbochargers are used to aspirate the cylinders on most commercial diesel engines. Technician B says that turbochargers can help expel end gas during valve overlap. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 32

Technician A says that valve overlap takes place as the piston completes its compression stroke. Technician B says that cylinder scavenging takes place at valve overlap. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 33

Technician A says that diesel fuel is composed of roughly 85% carbon. Technician B says that diesel fuels commonly contain around 15% hydrogen. Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 34

Technician A says that the greater the temperature difference between the cylinder temperature on the compression stroke and the firepoint of the fuel, the longer the ignition lag. Technician B says that a typical diesel fuel formulated for on highway use has a firepoint of about 250 degrees Celsius (482 degrees Fahrenheit). Who is correct?

A) Technician A only
B) Technician B only
C) Both A and B
D) Neither A nor B

Question 35

What is the term used to describe the tendency of an object at rest to want to stay motionless?

A) inertia
B) static friction
C) surface tension
D) stiction