You may use 2 Measurement Sensors. or may create an angular displacement plot and insert that value in expression. Please share model I will see that
I am not that much into Motion Analyses but I do have a suggestion.
Make a cylindrical dummy part at mate it to your crankshaft with a gear mate with a ratio of perhaps 1:10 or whatever is appropriate. Then set the trigger to this part. Perhaps you would need to make several triggers but again; how many revolutions must you have in your analyses?
Please let us know your progress and if possible upload your assembly. I - for one - would like to see this scenario.