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How do folks?

This is on behalf of a mate of mine, can any of you lot help him out??

Cheers Geo.


I'm just in the process of fitting an ISSPRO programmable tachometer, and have come into a little difficulty. This type of tachometer is very adjustable and can be set to measure between 1 and 255 pulses per revolution, and so could be used on any engine with a suitable signal generator. As I have a standard 2.25 petrol I connected the "sensor" wire to the negative on the coil. I assumed that as the engine fires two sparks per rev' I should set the sensitivity to 2, but the gauge went off scale. After a quick flick of the switches I found that 16 pulses per rev' gave the best reading at idle, but on the run into work today it was only reading about 2,600rpm at 50mph. My old tacho used to read about 3,000rpm for the same speed. A quick check of the maths said I should reset the sesitivity to 14 to increase the reading to 3,000, but then I think it would read too high at idle. Geo reckons the difference is due to the greatly increased scale of this new gauge over the old one, but I'd like to get it right.

Does anyone out there know how many "pulses" a coil should make per engine rev?
Or has anyone else with a SWB got a tacho and could give me some rev to speedo readings in fourth gear?


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