Tming is controled solely by the chip based on input paramters. It is NON user adjustable (Most chips nowadays you can adjust the timing but not really in a mechanical way)
Timing will vary as well, for example (Example only!):
Idle - 35 deg
Cruising - 40 deg
Full boost/load - 21 deg (first gear)
Full boost/load - 20 deg (second/ third gear)