Did you use a strobe? That is calibrated with a calibrated frequency counter? What percentage was it calibrated to? You see where im going here?
I use to be an electronic tech in the industrial field that performed calibration of instrumentation and sensors.
It gets really expensive the tighter the tolerances of calibration are calibrated to. The equipment to perform the work can get very expensive.
But again we are just dealing with 30-40psi and 10% error really isnt that big of a deal clocking in at 3-4psi or less error.
No, my tuner used HPTuner's scanner. I totally get what you're saying about things being calibrated to fine tolerances.
My ASSumption is that the margin of error of everything between the crank sensor and the pcm is +or-25RpM ...
and somewhere between the pcm and the tach needle, the lower margin of error swells to ≈300RpM.
(So far as we could tell, the needle never overestimated, by the way.)
Points I were trying to make prior:
can't JUST look at a 2 decade old mechanical dashboard gauge and assume it is accurately measuring, much less representing,
the actual oil pressure at that point of measurement, without at least one other measurement to compare it against.