Engine Performance
Work Example 6

WorkKey Level: 3
NATEF Automotive Tasks: VIII.A.8

The following are results from a cylinder power balance test.  Fill in the chart and determine which cylinder is weakest.

Cylinder Number	Idle Speed	RPM it dropped to	Difference between idle speed and test speed
1	850 rpm	720 rpm
2	850 rpm	700 rpm
3	850 rpm	780 rpm
4	850 rpm	695 rpm

Solution:

Students need to subtract to find the differences.
850 – 720 = 130 rpm
850 – 700 = 150 rpm
850 – 780 = 70 rpm
850 – 695 = 155 rpm

To determine which cylinders needs further inspection, you are looking for the cylinder with the least drop; therefore, cylinder 3 needs further inspection.