Deck 19: Producing Power: Valve Timing, Power and Torque Measurement

Question 1

Technician A says excessive valve lift causes piston-to-valve interference. Technician B says high valve overlap can lead to clearance problems between the valves and pistons. Who is correct?

A)Technician A
B)Technician B
C)Both technicians
D)Neither technician

Answer 1

B

Question 2

What are the two types of hydraulic phasers?

Answer 2

The two types of hydraulic phasers are:
oil pressure actuated (OPA)
cam torque actuated (CTA)

Question 3

Net horsepower is the power lost through friction in the driveline and due to wind resistance, vehicle weight, tires, and weather.

Answer 3

False

Question 4

Technician A says changes in cam timing are made to improve high-performance operation. Technician B says the computer advances the cam and high rpm and low load. Who is right?

A)Technician A
B)Technician B
C)Both technicians
D)Neither technician

Question 5

What term refers to the intake and exhaust valves being equally open at TDC?

A)neutral LCA
B)advanced cam
C)retarded cam
D)split overlap

Question 6

Power produced at the crankshaft with only the alternator and water pump drawing power is called _____.

A)gross horsepower
B)indicated horsepower
C)brake horsepower
D)raw horsepower

Question 7

What is a pumping loss?

Question 8

What are three types of variable valve timing?

Question 9

Variable timing of the exhaust lobe is used to control torque.

Question 10

What value is determined by multiplying the lobe lift by the rocker arm ratio?

A)total valve lift
B)gross valve lift
C)net valve lift
D)rate of lift

Question 11

Technician A says the effective compression ratio is determined by the point at which the intake valve closes. Technician B says effective compression ratio and static compression ratio are synonymous terms. Who is correct?

A)Technician A
B)Technician B
C)Both technicians
D)Neither technician

Question 12

Compression ratio affects the amount of power an engine can produce by increasing the thermal efficiency of the engine.

Question 13

All of the below are factors in camshaft performance EXCEPT _____.

A)duration
B)rate of lift
C)overlap
D)valve size

Question 14

Some aftermarket camshaft sprockets for OHC engines are adjustable.

Question 15

List three methods of adjusting cam phasing.

Question 16

Technician A says running a dynamometer test is noisy. Technician B says carbon monoxide (CO) is a major concern when using an engine dynamometer. Who is correct?

A)Technician A
B)Technician B
C)Both technicians
D)Neither technician

Question 17

Technician A says thermal efficiency is the ratio of how effectively an engine converts a fuel's heat energy into usable work. Technician B says the thermal energy of gasoline is about 50,000 BTUs per pound. Who is correct?

A)Technician A
B)Technician B
C)Both technicians
D)Neither technician

Question 18

What term refers to how fast motion is produced against a resistance?

A)force
B)power
C)torque
D)inertia

Question 19

The camshaft is the determining factor in how efficiently the engine pumps air while operating at various speeds.

Question 20

What is the formula for mechanical efficiency?

Question 21

Which dynamometer design deals with higher loads more effectively: water brake or eddy current?

Question 22

The work efforts needed to move air into and out of the cylinder are called _________ losses.

Question 23

Technician A says that it is normal for the piston to remain stationary at TDC for a few degrees of crankshaft rotation. Technician B says that if the intake valve is open more at TDC than the exhaust valve, the cam is retarded. Who is right?

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

Question 24

What is the term that describes the part of the power stroke between the time the exhaust valve opens and the piston arrives at BDC?

Question 25

High rpm power is improved by _____ cam timing.

A)retarded
B)advanced
C)neither of the above

Question 26

Technician A says that the rpm range of the engine is controlled by the point where the intake valve closes. Technician B says that closing the intake valve later in the compression stroke lowers the effective compression ratio. Who is right?

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

Question 27

Both of the following cams have intake and exhaust lobes of identical lift and duration. Which has more overlap, the camshaft with lobe centers at 112° or the camshaft with lobe centers at 114°?

A)112°
B)114°

Question 28

What is the term that describes the camshaft position when the piston is at the top of the intake stroke, the intake valve is beginning to open, and the exhaust valve has not yet finished closing?

Question 29

What is the name of the one camshaft angle that is measured in camshaft degrees instead of crankshaft degrees?

Question 30

Camshaft timing readings on OHC engines are taken before/after (choose one) the cylinder head is installed.

Question 31

The usable horsepower at the crankshaft is known as ____.

Question 32

A change of 0.001" in valve lash will result in approximately _____° of duration change.

Question 33

What would be the valve lift with a 1.5:1 rocker arm ratio and 0.300" of lobe lift?

Question 34

On the intake stroke, a big gulp of air happens when the piston reaches its maximum velocity at ____° of rod angle.

Question 35

To improve idle quality on longer duration cams, _____ lobe centers are used.

A)wider
B)narrower
C)Lobe centers do not affect idle quality.

Question 36

Which engine can achieve higher crankshaft rpm, one with a short stroke or one with a longer stroke?

Question 37

Closing the intake/exhaust [choose one] valve too soon can increase detonation.

Question 38

When inertia from exhaust gas exiting the cylinder sucks out even more exhaust, this is called ___________.

Question 39

When a cam lobe is ground differently on its opening and closing sides, this is known as a(n) _____ cam lobe.

Question 40

The timing of the camshaft events is listed in camshaft/crankshaft (choose one) degrees.

Question 41

Which of the following can cause clearance problems between the pistons and valves?

A)High valve overlap
B)Excessive valve lift
C)Both A and B
D)Neither A nor B

Question 42

Two technicians are discussing how excessive valve overlap affects a turbocharged engine. Technician A says that a turbocharger operates on backpressure in the exhaust. Technician B says that if the turbo operates at too low an rpm, backpressure can flow through the open exhaust valve into the intake air stream, limiting boost pressure into the cylinder. Who is right?

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

Question 43

Which of the following is/are true when measuring camshaft duration?

A)SAE specifications are measured after the valve has lifted 0.060".
B)High-performance camshafts are usually measured for duration at 0.050" lift.
C)Both A and B
D)Neither A nor B

Question 44

Which of the following is/are true regarding lift and duration?

A)Increasing duration can cause a rough idle and ruin low-end performance.
B)Increasing valve lift can cause a rough idle and ruin low-end performance.
C)Both A and B
D)Neither A nor B

Question 45

Which of the following is/are true about a cam with less overlap?

A)There will be more pressure in the cylinder at lower rpm.
B)There will be greater torque at low rpm.
C)This fits the profile of an RV camshaft.
D)All of the above
E)A and B only