Andrey has also much more stable engine phase angle reading algorithm
Indeed I noticed that the phase angle speed or rpm is too much noisy for a physical value. I guess (!!) that value is given through an instantaneous and simple computation of the time derivative of the phase angle.
Next, possibly, these values are averaged to make a reference fo the next revolution.
Equally we havegot some delay for the engine to start because during this starting mode the computed speed is much changing especially when we have few triggers.
If this is the case, this is an old story from the sixties ( I was dealing with dynamic ship positionning systems some years ago) People use Kalman filters (or so) to mild the data with a mixed of prediction based on a simple physical model (one mode) and of measured data, or even a serie of those filters with the combination parameters being scaled according to the speed.
Kalman was American, but Russian know the same technic very well.
Philippe