I've always wondered about calibrating the tachometer. Adjusting it based on your speedo. But I've never trusted my speedometer. I don't have any mile markers in my area to check my speedo. I've contemplated rigging up a temporary tach to my half-shafts to get wheel rpm. This way I could check both speedo, and tacho. But I 've always had other projects to consume my time! Can somebody tell me, is the tach pulse driven or voltage driven? Does the W terminal issue a variable voltage, or a frequency? I suppose I will need to test this myself... opps, I can't until my car gets back on the road. snip... The Quantum tach is calibrated >for the pulley ratios of the Quantum alternator. It was way off from the >needs of the Vanagon pulley system. I anticipated this and while I had >the tach out of the housing I drilled a small hole in the back of the >housing. This hole lines up with an adjustment pot in the tach. I can >just reach it with a small screwdriver and change the setting as needed. >I used a tranny gearing chart and measured the circumference of my >wheels. I then calculated the engine rpm at 65 MPH in 4th and adjusted >the pot a few times until it was right. > >Mark > -Gary, San Diego 1979 Rabbit 1.5 dsl, 180,000mi(sold) 1981 Rabbit 1.6 dsl, 150,000mi(sold) 1985 Quantum 1.6 td, 145,000mi(current)
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