So I've got this tach from a Quota...

[felix42o]

Awhile back, I bought a known good tach from a wrecked Quota. It works (technically) in the v11, but the quota must have used a different ECU, as the rate the tach swings is much faster than it should be. In other words, once started, it shows an idle of roughly 2500 RPM, and moves very quickly towards redline with only a slight increase on actual engine speed. So. Any thoughts on a way to "calibrate" this tach to work properly with the 15M ECU's signal? Is it as easy as adding a resistor inline(although I'm sure it's probably not that simple) or should I just scrap the thought and sell the thing on eBay?

[gstallons]

Probably.

[fotoguzzi]

the Q doesn't use the 15m cpu?

[Tom M]

I don't know if your tach can be recalibrated but I may know why you're seeing the problem. The V11 ignition fires the plugs on both the compression and exhaust strokes (wasted spark). I'm guessing that the Q only fires on the compression stroke so the tach is reading twice the actual rpm. Maybe there's a device out there that can cut the number of tach pulses in half?

[felix42o]

the Q doesn't use the 15m cpu?

I'm not sure one way or the other...just a guess. It's probably like Tom said, with the extra tach pulse. Not a huge deal here, but alot of you out there are pretty savy with this stuff. Figured I'd throw it out for consideration before getting rid of a working tach.

[fotoguzzi]

I don't know if your tach can be recalibrated but I may know why you're seeing the problem. The V11 ignition fires the plugs on both the compression and exhaust strokes (wasted spark). I'm guessing that the Q only fires on the compression stroke so the tach is reading twice the actual rpm. Maybe there's a device out there that can cut the number of tach pulses in half?

 

I can't believe there is any difference like that between the two motors..

[Guzzi2Go]

the Q doesn't use the 15m cpu?

I'm not sure one way or the other...just a guess. It's probably like Tom said, with the extra tach pulse. Not a huge deal here, but alot of you out there are pretty savy with this stuff. Figured I'd throw it out for consideration before getting rid of a working tach.

There is a sticker on Veglia tachs telling you "how far at what frequency". As I can recall it was something about 366Hz@11000 RPM.

 

If it is about cutting the frequency in half, then a simple counter can help you (Counter). Simple counter can be realised using something like 4013