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Condezeca

Veglia rev counter showing half revs

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   Hi mates, anyone knows what to do on a Veglia that start to shows half of real engine revs? That is from my 2000 V11 Sport.

   Thanks in advance for your help

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Mine does somethnig similar, but I've only check it at idle speeds while comparing with GuzziDiag...

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It is common that the Veglia is not accurate (Vague-liar! :grin:).

If it is a sudden change, upgrade Relay #2 (and the rest!) to the "Best Relay."

Condezeca,  what did you use to compare to the Veglia?

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Just had a look at mine.

At fast idle ecu says 1100rpm, dial says 500rpm and signal going into gauge (yellow and black wire) is 34hz.

No idea what the correct frequency should be?

I am assuming it goes up with rpm as it doesn't look like a pwm signal.

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Just to follow on, 34hz is 2040 pulses per min, so for a 2 cyclinder motor, 1020rpm. Pretty close.

So given the pulse train from the ecu into the gauge is right, has anyone opened up a Veglia tacho? I would imagine a dry capacitor would cause it to read low...

 

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Low Voltage at the gauge might make it read low but I suspect it would read erratically 

The pulses to the tach come from the ECU, I doubt it would be missing pulses.

Sometimes an erratic tach is a sign of charging or headlight problems, the Tach is powered off the headlight relay which also acts as Voltage reference for the Voltage regulator, check the Voltage at the female connector of the regulator M/Fm socket.

Otherwise Rich888 might be right something inside is drifting, I just recently repaired the Veglia off my 72 Eldorado 

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Here's a vid showing how far out my tacho is from my homebrew all electronic tacho:

https://youtu.be/XXqWtwz_LTQ

 

Eventually hope to replace the analog tacho with a digital version that will have serveral readouts on...

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Mine died shortly after this began. Coil wire was broken.

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Using my homebrew datalogger, I noticed that the RPM value reported by the ECU also has glitches in:

 

image.png

 

Not sure if this helps explain the dodgy Tacho Gauge or is some other issue?

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the conversation is way above my pay grade, but I'm following your projects with much interest. thanks for taking the time, and for posting.

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13 hours ago, rich888 said:

Using my homebrew datalogger, I noticed that the RPM value reported by the ECU also has glitches in:

image.png

Could this show a defective RPM sensor?

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5 hours ago, MartyNZ said:

Could this show a defective RPM sensor?

Maybe.

The glitches get progressivley bigger as the RPM's go up.

I assume the ECU measures RPM from the crank sensor (TDC sensor). If it is actually reading these glitches, I would expect it to cause glitches in fueling too...

I would assume that the TDC sensor provides pulses, so don't know how it could trigger early and then late? Mabe the ECU is doing some averaging and getting it wrong!??

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Just for interest, this is a log of a gearchange:

 

image.png

Speed is updated every second via GPS - hence the steps!

There are some disturbances in the injector timings but hard to say if they match RPM glitches.

The sample rate is too slow to be sure at only 15 times per second, but I have just improved that to 30 times per second, so it may show up better... When it drys up a bit outside, I'll take another plot and keep the bike in a lower gear to keep the rpms in the 5000-6000 band for longer.

I'm actually looking for the reasons for the occasional missfire / hiccup as well as the misbehaving tacho.

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