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Veglia rev counter showing half revs


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2 hours ago, rich888 said:

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!??

I always wondered what a worn cam chain and tensioner could do to affect timing of the camshaft and phonic wheel. Perhaps a loose chain whipping about could cause the glitches you see?

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Hi mates,    Just solved the issue on my rev counter, hope can help anyone with same kind of problem.  I opened the rev and and found that one of the 3 weights in the arm of the needle was o

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

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 tha

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2 hours ago, MartyNZ said:

I always wondered what a worn cam chain and tensioner could do to affect timing of the camshaft and phonic wheel. Perhaps a loose chain whipping about could cause the glitches you see?

Not thought of that!

It's not going to be easy to verify the TDC sensor operation, will probably have to datalog the pulse timing from it directly, together with the ECU RPM values.

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10 hours ago, rich888 said:

It's not going to be easy to verify the TDC sensor operation, will probably have to datalog the pulse timing from it directly, together with the ECU RPM values.

Mad bunny showed an oscilloscope trace of the sensor output here:

https://www.v11lemans.com/forums/index.php?/topic/20673-mgs01-no-spray-no-spark/

It's a different engine, but the sensor is the same.

 

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5 minutes ago, MartyNZ said:

Mad bunny showed an oscilloscope trace of the sensor output here:

https://www.v11lemans.com/forums/index.php?/topic/20673-mgs01-no-spray-no-spark/

It's a different engine, but the sensor is the same.

 

Thanks! I will stick a scope on mine today.

Do you know if the Tacho signal from the ECU is derived directly from the TDC sensor or generated by the ECU software?

 

I'll scope both and see what they look like....

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34 minutes ago, rich888 said:

Do you know if the Tacho signal from the ECU is derived directly from the TDC sensor or generated by the ECU software?

I don't know what the ECU does with the sensor signal. All I know is the sensor RPM & TDC signals go into the ECU pins 7 & 12, and the ECU output to the tacho is from pin 3.

Meinolf has delved into the ECU,  so perhaps he can help you. 

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4 minutes ago, MartyNZ said:

I don't know what the ECU does with the sensor signal. All I know is the sensor RPM & TDC signals go into the ECU pins 7 & 12, and the ECU output to the tacho is from pin 3.

Meinolf has delved into the ECU,  so perhaps he can help you. 

So there's a TDC and RPM sensor?

I was looking at the service manual for a 2002 V11 LeMans and found item 34 Phase/Revolution sensor. 

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14 minutes ago, rich888 said:

So there's a TDC and RPM sensor?

I was looking at the service manual for a 2002 V11 LeMans and found item 34 Phase/Revolution sensor. 

Maybe there are two sensors in the one housing...

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13 hours ago, rich888 said:

So there's a TDC and RPM sensor?

I was looking at the service manual for a 2002 V11 LeMans and found item 34 Phase/Revolution sensor. 

No, sorry I didn't make it clear, one single coil sensor detects both TDC & RPM. The phonic wheel has one odd tooth that tells the ECU phase/TDC, and the rest of the teeth tell the ECU the RPM/revolutions. A oscilloscope trace shows one offset pulse per wheel revolution (which is half crankshaft speed).   

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Got my datalogger to record the tacho signal directly and this is the log:

 

The green trace is RPM reported by the ECU. The red trace is RPM calculated from the frequency of the tacho signal.

 

I also found that the tacho signal can't handle much of a load. An extra 5mA load of the opto isolator led I'm using is enough to drop the tacho voltage down sufficiently to stop the tacho dial working.

 

Anyway, it seems clear that the glitches reported by the ECU are not there on the Tacho signal!

Need to check the RPM/TDC signal too.

 

Question is, is the ECU reporting the glitches because its using this value of RPM in computing injector timing? I need to repeat the logging with injector timing to check...

 

RPM from ecu and tacho.jpg

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Here's a plot showing injector timing too. Looks like the glitches reported by the ECU are just errors. Doesn't seen to change fueling...

This is 32 seconds long, with two gear changes. The glitches are there in blue and the red trace is the tacho signal to the rev counter. Green is injector pulse duration.

 

 

guzzi glitches.jpg

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So where exactly do you pick up the signals? Between sensor and ECU or between ECU and Tach? As written by others further above the wheel/sensor feeds the ECU, the ECU feeds the tach. Go on MyECU.biz for further infos and details. This man knows his stuff.

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On 5/9/2019 at 6:25 AM, MartyNZ said:

I always wondered what a worn cam chain and tensioner could do to affect timing of the camshaft and phonic wheel. Perhaps a loose chain whipping about could cause the glitches you see?

 

On 5/9/2019 at 9:02 AM, rich888 said:

Not thought of that!

It's not going to be easy to verify the TDC sensor operation, will probably have to datalog the pulse timing from it directly, together with the ECU RPM values.

I dug out my old timing light, pulled the bung out of the RH side of the bell housing, and ran the engine from idle up to 5000 rpm while watching for erratic movement of the flywheel teeth under strobe light. Sure enough, the gear teeth didn't move smoothly, but jumped around erratically.

The only reason I can think of that causes that is a worn cam chain & tensioner. The bike has done about 80 000 km.

Unless someone can think of another reason, I'm changing these parts this winter.

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The wheel resp. the mark probably is jumping mostly because of running the engine without load. The risk of doing something silly to your engine while opening it just because of that definitely is bigger then any possible gains.

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9 hours ago, luhbo said:

The wheel resp. the mark probably is jumping mostly because of running the engine without load. The risk of doing something silly to your engine while opening it just because of that definitely is bigger then any possible gains.

I respectfully disagree. Timing chain/tensioner is a simple job, and it sounds to me that it may be in order..

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It's a simple job, agreed. That doesn't mean it's going by itself. It's about the gains in this game. Chain and tensioner are rock solid, easily making 200.000 plus. Not without wear, but still doing their jobs.

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