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Hi all,
This ones got me a bit stumped. Im wondering if anyone knows what the markings on the tacho under 1000 rpm represent. I set my idle to what i think is 750 rpm today....but looking at everything above 1000 rpm, the small markings indicate 250rpm increments. Being a sweeping gauge, they are all evenly spaced...except for the markings under 1000 rpm. My question is...are the markings under 1000 rpm still in 250 rpm increments? Or are they physically measuring closer together, in smaller rpm increments, to aid in setting idle (not to mention the fact that an engine probably wont idle under 300rpm successfully, so theres no need to have markings that low).
The physical distance between 1000-1500rpm is the same as 1000-0rpm (50% ratio difference) so do the marking under 1000 rpm still represent 750, 500, 250 and 0...or is ot more like 875, 750, 625, 500>?. Being a sweeping and calibrated gauge, i struggle to see how the rpm increments under 1000rpm could vary to the rest of them...
The marks below 1,000rpm are in 250 increments. It's a d'Arsonval gauge, so it's slightly non-linear near the bottom.
Of course, the width of the needle is more than the distance between 700 and 850, so you're not going to get that sort of precision from a gauge like this. So if you care, you should use a "real" rpm gauge. But don't expect magic. At 600 rpm the coil is firing 30 times per second, so if your digital gauge is updating a sluggish once/second, it's displaying "600" based on only 30 counts. So 31 counts would cause it to display "620." You get the idea.
05-11-2016, 02:10 AM
