and calculates zphase at that point for each phaser the zphase value for each phaser is then made accessible by the controller for subsequent use after the zphase values are saved for all speed ranges the method is then performed in its normal fashion i e without zphase corrections it is noted that the method may be embedded in control software adapted to be used by a controller such as an engine control unit the saved zphase values or points are interpolated between the 500 rpm thresholds over the 500 to 6000 rpm range these interpolated values are used when calculating the phase measurement by a controller such as the ecu referring to fig4 a diagram 90 shows the relationship between engine crank speed and zphase value a number of testing points are depicted on curve 92 for example point 94 may denote crank speed at 500 rpm having a corresponding zphase value as can be appreciated the variation of zphase values occurs at only a segment of curve 92 i e the low engine speed range these points that are shown in diagram 90 are used for zphase calibration and for values between the points interpolation method are used the values corresponding to the points may be stored in a non volatile memory such rom or eeprom.