Compression & Power Balance (Picoscope) - Monday 20th October 2014

Picoscope Pattern
Compression Test

Today I resumed the Compression Test task by hooking up a Picoscope to the Endura-E 1.25 engine rig I was working on.  These tests are located by accessing Pico Diagnostics from the main screen icons.  The compression test is conducted in the same manner ie; with coil disconnected and fuel supply disabled, however the spark plugs remain intact. This is done by connecting an Amps Clamp around the positive battery lead, and then hooking this up to the Picoscope via Channel A directly.  With the throttle wide open as before, the engine is cranked and the Picoscope then measures the Amperage used to reach maximum compression on each cylinder stroke.  The results are displayed in a bar graph format but do not indicate which particular cylinder has a loss of compression, only that there is a loss of compression indicated.  This is a computer timed test and produces an image upon its own conclusion.  These tests would be of most practical use to initially test a Diesel engine, where the time and cost involved in removing the various components to test traditionally could prove an otherwise unnecessary procedure, and at expense of the service provider concerned. 

Picoscope Pattern
Power Balance Test

The Power Balance test is conducted with the engine running.  The Picoscope is connected via crocodile clips to both the Positive and Negative battery terminals directly to Channel A of the scope.  The results are displayed live and the "space bar" needs to be pressed in order to capture a good image.  As in the Compression Test the graph will only indicate an engine imbalance, rather than pinpointing any particular cylinders, however it is useful in ascertaining a particular issue prior to investing time and money into its further investigation.  Having also fully tested the exhaust extraction system of Workshop 3 to its fullest capacity with Carl Black, the area was duly vented before I could then see the Job Card to write it up and be signed off as complete.