Compression Testing and Engine Timing Videos

Frank Massey, from ADS, gives us an in-depth analysis of Engine Compression Testing and related Timing. Have a look at the WPS500X Pressure Sensor for more information on the transducer used in these videos.

Episode 1: Engine analysis with PicoScope

Frank shares his views about the theory and terminology behind engine analysis with oscilloscopes. He advances the proposition that there is no such thing as 'vacuum', 'suction' or 'negative pressure' but proposes that we think of pressure as absolute, i.e. a hard vacuum is zero pressure. Differences in pressure produce flow.

Running time: 3min 54s.

Episode 2: Relative Compression Test

Frank talks about relative compression testing with PicoScope and PicoDiagnostics. Misfires generally stem from ignition, fueling or mechanical issues. A relative compression test removes the first two and definitively points to a mechanical issue.

Running time: 4min 44s.

Episode 3: Compression analysis using PicoScope

Frank demonstrates PicoScope Software. PicoDiagnostics measures battery voltage and current when cranking to measure a drop in compression in any of the cylinders.

Running time: 9min 10s.

Episode 4: Compression Analysis using the WPS500X

Frank uses the WPS500X to capture the real-time, absolute pressure in Cylinder 1 on a running car. The WPS500X provides an accurate absolute compression pressure, which can be extrapolated across all cylinders. Furthermore, the in-cylinder pressure waveform can reveal any inlet and exhaust restrictions. Some surprising deductions as to when exactly the exhaust and inlet valves actually open are explored.

Running time: 23min 49s.

Episode 5: Electronic Engine Synchronisation

Frank analyses CAM and crankshaft correlation. On some vehicles the sensor may not actually measure the shaft position and the ECU might change the shaft position relative to the sensor. The best advice is: use the PicoScope waveform library and download known-good results for comparison.

Running time: 10min 28s.

Episode 6: Combining your Evidence

Frank's last episode of pressure testing with a PicoScope covers combining your physical and electronic evidence. A pressure waveform allows you to ascertain engine timing to a far greater degree of accuracy.

Running time: 8min 02s.