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Thread: Distributor advance curve
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10th Nov 2021, 08:00 PM #1
Distributor advance curve
hi
I need to test or calibrate a vintage automotive distributor advance curve against the specs. , this is a mechanical advance only, no vacuum involved . There are two weights and springs that move and rotate a plate according to the applied RPMs.
I can easily spin the shaft with a drill and I have a cheap digital tacho device.
So if I mark the plate and the outer housing with a marker pen at a reference zero or RPM zero and also mark degrees around the circumference of the housing. I should then simply watch to see how far the plate moves at a given RPM.
Any thoughts ?
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11th Nov 2021, 04:12 PM #2
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12th Nov 2021, 08:18 AM #3Mechanical Butcher
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A strobe lamp triggered by spark event could help, if a degree wheel were attached to the same shaft as drives the dizzy.
Note that you should double the tacho reading to translate to rpm at crankshaft.
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12th Nov 2021, 12:06 PM #4
Ok
OK yes, basically, that is the method the article I linked to is describing.
Somebody on a forum described a method of testing the advance curve using a dual trace oscilloscope, he compared the two signals and worked out the degrees of delay, he used a opto coupler to trigger the CRO.
Years ago, there were special distributor testing machines made by SUN Co. Tuning business/garages used to use the SUN machines to check the advance curve and other parameters. Some of the more expensive digital readout timing lights you can buy these days have a built in advance readout mode, it displays the advance on a screen.
These days cars have on-board computers that do it all , the computers do the timing adjustments automatically !
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