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Base timing changing for no reason


letitsnow

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There's something weird going on, the base timing keeps changing on me. The dizzy is locked down and the sensor is bolted in tight. A few days ago I checked the timing because I thought I heard it pinging in boost, it was advanced, I adjusted the trigger angle to correct it. Today I checked again, it was retarded 8*, I adjusted the trigger angle again, 8* change, it moved 10, dialed it back a bit, no change, I set it back to the number I started with, but now the timing is correct.

 

So the series of events went like this today:

timing light reads 12*(20 commanded)

change trigger angle from 329 to 321

timing light reads 23*

trigger angle to 324

little/no visible change

trigger angle to 329

timing light reads 20*

 

MS2 v3

wasted spark

DIYAT wheel in the turbo dizzy

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Are you looking at the actual spark advance in Tunerstudio, and not just looking at where it should be according to your table? I ask because there are ways to advance/retard timing based on IAT or CLT temperature or afterstart conditions.

 

I'm not sure if it matters, but your trigger angle is high. Mine is set to 59.5, which is almost a whole revolution of the dizzy back from where yours is set. Granted you have a different trigger wheel than the stock one I am using.

 

I've also heard of the damper/crank pulley slipping as the rubber ages, which can cause your timing marks to move, but I would think this would only be a problem under heavy load, not at idle as I presume these readings were taken at.

 

Other than that stuff, the only things I can think of is either the whole distributor moving, which you said it is not, or the trigger wheel itself spinning, which is not likely because it has a D slot in the center.

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