ACT Work Keys Level: 5

NATEF Task(s): VIII.A.6

Problem

A technician is doing a cylinder balance test on a 6 cylinder engine. Before performing the test the technician notes an engine RPM of 750. The RPM readings for each cylinder during the test are:

1) 680 RPM
2) 650 RPM
3) 660 RPM
4) 638 RPM
5) 733 RPM
6) 668 RPM

1. Did the engine pass the test? Show your work and explain your answer.

2. Which cylinder is doing the least amount of work? Explain your answer.

Solution

1. Calculate the percentage difference between the highest and the lowest cylinder RPM reading.
   638/733 = 87%
   100 – 87 = 13%
   Since the percentage difference between the two cylinder's RPM reading is greater than 10%, the engine fails the test.

2. Since the RPM reading dropped the least with cylinder 5 disengaged, cylinder 5 is doing the least amount of work.