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G4+Storm running a Nissan VH45DE(+T).   Engine  has been running on a rough initial starting, warm up and idling tune only. Went to  recheck the trigger calibration with a timing light while idling at normal temp and found the engine running slightly advanced by approximately 3 degrees from my initial calibration set up. However when putting the engine in "set base timing" mode another  timing light check shows the timing marks (15 degrees BTDC) spot on again??

My first question is do I just leave the offset setting as is when in "set base timing" mode and ignore the obvious timing mark misalignment under normal conditions or the opposite? I've found I can get the marks aligned reliably under normal conditions by factoring in the 3 degrees when in "set base timing mode".

Second question related to this is the ignition timing delay setting. Again, when locked, no movement between timing marks but in normal running mode it moves with throttle input regardless of the delay setting entered.

I'm using the OEM Nissan CAS fitted with a 24 tooth disc, have had no problems with the triggers since being set up with the engine running fine apart from this discrepancy since. 

Am I missing something?

Cheers, Pete.


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When you have it in set base timing mode, you garauntee the timing will be at 15*. Sounds like at this time, you do have stable timing. This means your trigger1 offset is correct.

When at idle, you are NOT garaunteed to be at 15* timing. If you are idling at 18* timing, you will be 3* ahead of your timing mark, exactly as you are seeing. You havent posted an idle log so I cant be sure, but looking at your ignition table, if you are idling above 1500rpm, or above ~50kpa MAP, then your timing will start to advance so 18* seems possible. 

without locking the timing, it will move around a bit at idle based on RPM and MAP.

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