Crank() function in Picoscope may help you find the TDC
This quote from diag.net/msg/m438upc23y… :
"I decide to get the cam/crank sync capture to compare to the known good I have for this engine. The signals are there and plenty strong enough to be seen by the ECM. ... I decide to use in cylinder pressure to determine where top dead center is. "
made me thinking -- information about where TDCs are is already there in the CKP waveform. As a cylinder approaches TDC at compression stroke, the crankshaft slows down, and this is reflected in the CKP waveform. For VRS CKP sensors and their digital siblings, Picoscope provides crank() function in the Math Channels. TiePie scope has a similar function implemented.
The number of teeth should be estimated from the zoomed-in CKP waveform.
Here is an example, which is not perfect -- it is a capture of an engine start at just 13kS/s, as described in article picoauto.com/library/case-s…
If we apply crank() function for it, we get this:
The valleys in crank speed show TDCs, and, not surprisingly, dips in the starter voltage on Ch. D (=inverted relative compression test) follow the TDCs as well.
The crank() function is not perfect; for example, it leaves area around the sync notch blank. It does not show which cylinder gets to TDC. Its precision is limited. But if it helps to identify the problem (e.g., the ignition event does not stay with one cylinder, but floats around instead) and allows to skip the in-cylinder pressure test setup, it's worth a minute or so it takes to apply it, right?