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So I'm in the process of fitting a 60-2 crank trigger, is there a 'rule of thumb' on which tooth after missing tooth to be allocated as TDC?
On a Gm ls3, it uses tooth #14.
For reference the crank trigger will be fitted to a 4 cylinder.
Modern EFI systems can easily handle any number of teeth between window and TDC. But don't forget about trigger and home signal correlation. Missing window shoulndn't appear in front of the sensor just before home signal occurs. Home signal should be the first one otherwise ECU will wait at least 1 crankshaft rotation in order to start counting. Everything will work in that case but that delay is totally useless.Try to achieve window appearing after home signal plus from quater to half of crankshaft rotation.
In the aftermarket standalone ECU world it doesn't really matter where you put the missing teeth in relation to TDC #1. You simply tell the ECU where TDC #1 is during the ignition timing calibration sequence. As stated already, the relationship between the missing teeth and the synchronisation sensor is important but the beauty of this style of trigger disc is that you have a lot of freedom with the sync location - Basically anywhere away from the missing teeth.
Considering most factory 60-2 crank triggers use between 8-15th tooth as tdc, I will aim for that.