Polaris, Trail Tech and other Tachos

[tz375]

Today I wanted to get an idea of how accurate or inaccurate the Trail Tech Vapor bar graph tacho is. I don't have a super accurate, calibration grade tacho, so I did the next best thing and hooked up a couple of other tachometers to use as a cross reference.

One was a simple TZR250 tacho with three leads and it turns out to be DOA. I should have tested it when it arrived. Ah well. That's ebay for you.

The next one I hooked up was a huge Polaris snowmobile 6 pulse tachometer. I like the in your face look of that tacho and it reminds me of a Vincent 5 inch speedometer (from a distance). It has two wires, one is to ground and the other is to the alternator, so I hooked that up to one of the three yellow leads from the GT alternator to the rectifier.

I fired the bike up and at a steady, 2000, 3000, 4000 revs both tachometers read the same. The Polaris XCR800 triple tacho appears to be a little over damped and rises rather slowly so it's probably not a great idea for a fast revving race bike, but for the street it would look great on a street tracker for example.

[CJF]

I originally planned to use a polaris tach on my build, but ended up going with an acewell. The acewell tach function works pretty well, but seems a little jumpy. I have a feeling that may be partly because I'm used to looking at a mechanical dial tach and now I'm looking at individual digital numbers as it runs up and down the rev range.

[tz375]

We used a digital AIM tach and data logger a few years ago and it drove me nuts trying to read numbers flashing up and down. Unfortunately that is probably the least suitable application for a digital readout. Digital is great for static state or where the rate of change is low. With a tacho the revs are constantly changing and that's very difficult to read.