CRIP angle

[benmtech]

This is not necessarily M1 related.... I have measured 2 similar engines from the same manufacturer with CRIP 5 deg apart.(Honda 600). The method I used is with a timing light where you can set the timing at a given number of degrees BTDC to that the light marks the TDC marks on the crank.I have to assume at this point that the cam timing is the same. I use the locking timing screen in M1 at 20 deg and set the timing light at 20 deg. One engine measures 461 deg (the normally accepted value) and the other measures 466 deg. That in itself is strange but by my reckoning, the 466 ignition table should be 5 degrees retarded overall in comparison with the same table using 461 CRIP. Is that correct? If that is correct at least the 466 will be a safer value to work with. Assume that there are no trims affecting the table either overall or pressure/temp comps. Its possible of course that my timing light is faulty but unlikely in this case.

[SOReilly]

Hi Ben,

Assuming that the ref/sync settings are identical and the only difference is the engine then the variation must be mechanical.

It may be helpful to use a piston stop and determine the true TDC position. Doing this may present a discrepancy between the external timing markings and the actual piston position.

[David Ferguson]

Any chance you are using a 36-tooth wheel, and a magnetic sensor with swapped polarity?

It may be useful to do an input capture and carefully study the polarity with respect to missing teeth.

[benmtech]

Thank you for your replies. I have already done REF/SYNC captures and both are identical. The active edges are set correctly. My question remains: With an increased CRIP value of 5 deg and supposing that is incorrect and it should be 461, does that shift the ignition table 5 deg retard as I suspect?