Trigger offset

Technical Area Forced Induction & ITB
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  1. My model of MX-5 is: NBFL 1.8VVt
  2. I’m based near: Chesterfield__
  3. I’m looking for technical help or recommendations on: __

Hi all. Just looking for ideas on what could be causing the trigger offset needing to be set 10° off what it normally is with a 36-2 trigger wheel. I’m part way through tuning my car with Alex Hickson. He says the trigger offset with that trigger wheel is normally 559 but I have to have mine running at 549 for the car to be running smoothly and 539 for the timing marks to line up when fixed fire mode is on. When at 539 the car does not run or drive well with fixed fire turned off.
I’ve found TDC with a screwdriver in cylinder 1 and put a new mark on the crank pulley and there is a 10° difference between that and the original marks on the pulley. Could it be that the crank timing belt pulley is a tooth out?

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Have you checked the timing belt pulley woodruff key/slot is not worn?

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No. I’ve always just assumed that was all ok as last year I had a new engine put in and they told me they had changed the cambelt.
When I fitted the trigger wheel I did notice there was no key on the timing belt pulley that the 5th hole of the trigger wheel sits on. Would that affect it at all?

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