RPM readings from ECU are glitchy

[rich4822]

I've been doing some simple datalogging and found some odd glitches on the RPM readings.

They appear to get bigger, the higher up the RPM range you get.

This shows a small sample during a gear change:





This is data read from the ECU via the OBD, on a V11 Sport.

I don't know if this real, as in a dodgy TDC sensor or if it's the ECU getting it wrong...

[beetle]

Are there any noticeable physical affects? Momentary hesitation, or stumble? If not, it's probably a sampling issue. What are you logging with?

[rich4822]

Are there any noticeable physical affects? Momentary hesitation, or stumble? If not, it's probably a sampling issue. What are you logging with?

The logger is homebrew and is limited (at the moment) due to the ECU's slow response time. So sample rate is about 30ms.

I am experiencing occaisonal stutters/misfires, which is one of the reasons I have be looking at datalogging, the other being ECU remapping.

[beetle]

What else are you logging? Do the glitches occur with any other data variance?

[rich4822]

What else are you logging? Do the glitches occur with any other data variance?

I'm logging TPS, Injector time, speed.

The sample rate is too slow to say for sure, but there do appear to be injector timing upsets too.






My sample time is only once per 5 revs when doing 4500rpm, so I am reworking the logger to measure signals directly instead of using the slow ECU diagnostics port.

[beetle]

Yeah, more data would help narrow it further. The injector glitch is suspiciously coincident with the RPM spike. You could be looking at a phase sensor or injector issue.

[rich4822]

Yeah, more data would help narrow it further. The injector glitch is suspiciously coincident with the RPM spike. You could be looking at a phase sensor or injector issue.

So here is ECU reported RPM (green) and the Tacho signal frequency, measured by my datalogger and converted to RPM (red).

No glitches!

Next I will add in actual injector pulse width measurements...

Sample rate is about 60 times per second, so about 2 per rev at 2k rpm






Heres the datalogger - work in progress at the moment, it's also a digital dasoboard!

[Kiwi_Roy]

Have you tried looking at it with a simple oscilloscope, perhaps you are getting false triggers.
Exactly what terminal are you reading from the ECU?

[rich4822]

Have you tried looking at it with a simple oscilloscope, perhaps you are getting false triggers.
Exactly what terminal are you reading from the ECU?

Yes, the scope doesn't tell me much as I can only look at one pulse. The datalogger times every pulse.

I'm looking at the tacho signal that goes to the rev counter and the RPM value reported by the ECU via the diagnostics. The values reported over the diagnostics port has the glitches in.

[Wayne Orwig]

So here is ECU reported RPM (green) and the Tacho signal frequency, measured by my datalogger and converted to RPM (red).

Are you saying that the tach pulse signal appears to have the same glitch?

I see an Arduino. I've been playing with a Nano board myself. Handy little thing.

[Kiwi_Roy]

Are you saying that the tach pulse signal appears to have the same glitch?

I see an Arduino. I've been playing with a Nano board myself. Handy little thing.

He said in reply No 6 the tach pulse has no glitch, both signals come from the ECU but i doubt the tach is through the processor, maybe just converted from a coil spike to square wave the glitchy signal would be numbers, no.

Its quite the project you have taken on Rich
Have you asked the guys over at VII Lemans.com they have been wrestling with spine frames for 30 years.

[rich4822]

He said in reply No 6 the tach pulse has no glitch, both signals come from the ECU but i doubt the tach is through the processor, maybe just converted from a coil spike to square wave the glitchy signal would be numbers, no.

Its quite the project you have taken on Rich
Have you asked the guys over at VII Lemans.com they have been wrestling with spine frames for 30 years.

Hi Roy,

Yes, I hve posted on V11 Lemans too...

The main experts on the ECU appear to be in Germany and have probably got fed up with me hassling them with loads of questions! 

Anyway, this is just a hobby for me, gives me stuff to learn and it's been interesting to find out about the ECU etc.

When I get the datalogger working with O2 sensors, I can explore remapping, but for now, I'm looking for the source of an occaisonal misfire.

I can set the logger up to record only at specific speeds or RPM's or it can record while I have a button pressed on the bars so I don't have to wade through tons of data.

I have a break out cable between the ECU and the main loom so I can easily get at any of the bikes vitals.

[Kiwi_Roy]

Cliff Jefferies MyECU site, gives a good explanation of his. I bought his kit-set for my VII before Guzzidiag was available.
I expect you have checked that out as well.

[rich4822]

This log shows more data with injector timings. No changes in fueling seen so glitches are just coming from the ECU... These will only be an issue for my digital dashboard are are so fast, I doubt I'll see them...

[rich4822]

I see you're not used to Guzzi gauges. The tach is only there to let you know the motor is running and the speedo is only there to  you know you are moving forward. Accuracy of either is suspect.

Ha! Yes, my gauges are very friendly, they are always waving at me...

[beetle]

So, just data glitches in the k-line? Well, at least you know there's nothing mechanically wrong.

 

[rich4822]

So, just data glitches in the k-line? Well, at least you know there's nothing mechanically wrong.

 

Yes looks that way...

Now to find out what happens when the motor hiccups when coasting... I need to pick up the ingition coil pulse for that...

[pauldaytona]

getting rpm is better to pick up the pulses on the injector. Same as on the coil, but the coil is a nasty signal. The injector is where I get the rpm from for my datalogging with a LM1

[rich4822]

getting rpm is better to pick up the pulses on the injector. Same as on the coil, but the coil is a nasty signal. The injector is where I get the rpm from for my datalogging with a LM1

Yes the coil drive has a peak voltage of 350v, but I want to know if the misfire is injector or ignition, so I want to look at both.

RPM from the tacho signal looks accurate and is free of glitches.

[beetle]

Nothing wrong with picking the coil pulse from the ECU side.

[rich4822]

Nothing wrong with picking the coil pulse from the ECU side.

Nope, but it is still a big ol' spike from the back emf.