Sync problem @ high rpm

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j.oe
Posts: 21
Joined: Sun Jul 15, 2012 12:19 pm

Sync problem @ high rpm

Post by j.oe »

After running in my forged engine i gave her some higher rpm pulls @ 0,3 bar to 1 bar only.
My rpm limit is set to 8k5. But between 7k5 and 8 k always the engine stuttered like running into an old school rpm limiter.
The recently taken data logs show that the rpm signal goes lost at the same moment. In order to investigate the reasons for i did another data log only recording the an01 (CAM signal) by 500 Hz, an02 (crank signal) by 1.000 Hz, rpm by 25 Hz and syncState, syncFault by EVENT. The rpm signal fails while the crank and cam values show valid signals. It's hard to record the crank sensor @ high rpm. 1.000 Hz sample rate doesn't relate well to 1.700 Hz signal frequency.

Here's the log: https://www.dropbox.com/s/qe76gfrzfy128 ... %230706.SD

Does anyone here have an idea, what's wrong ?
By the way: The cam- and crank sensors already got changed.

Cheers Jürgen
pat
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Re: Sync problem @ high rpm

Post by pat »

Jürgen,

Sampling crank or cam as an analogue voltage even at 1kHz is not going to help. That is why there is the SyncScope which can sample these signals up to 100kHz. When you lose sync, use Device -> View SyncLog and then hit the Error buton to see what led up to the sync loss. Typically you may find some noise with sufficient amplitude to trigger a phantom tooth or you may find a magnetic bias that raises or lowers the signal thus preventing it from registering a valid tooth. The log will tell us what to adjust on the thresholds.

Hope this helps,

Pat.
j.oe
Posts: 21
Joined: Sun Jul 15, 2012 12:19 pm

Re: Sync problem @ high rpm

Post by j.oe »

Thanks Pat,

I will do so and report to here, what i've found.

Jürgen
j.oe
Posts: 21
Joined: Sun Jul 15, 2012 12:19 pm

Re: Sync problem @ high rpm

Post by j.oe »

Well, here's what i've found from the sync fault event yesterday:

TXT-File of the exported log: https://www.dropbox.com/s/4oxalby8bfzn7 ... 5_1743.txt

And here the screen shot of the syncError window:

https://www.dropbox.com/sh/g1ncwyo6shmb ... 5_1743.jpg

Looks like there were a changing Bias between 0.5 to 1 Volt strangly rising up to 5 V at the end.
I hope, that helps.

Thanks Jürgen
pavlo
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Re: Sync problem @ high rpm

Post by pavlo »

The bottom half of the window shows your cam signal with plenty of noise prior to rising up, then it flatlines at +5v because it's saturated the input.

Do you have a cal file for this?

What are you cam(phase) sensor voltage thresholds?
j.oe
Posts: 21
Joined: Sun Jul 15, 2012 12:19 pm

Re: Sync problem @ high rpm

Post by j.oe »

Hi Pavlo

High voltage threshold for the cam phase sensor actually is set to 1.4V.

Here's my CAL-File: https://www.dropbox.com/s/poqvkveu786nh ... Juergen.SC

Jürgen
j.oe
Posts: 21
Joined: Sun Jul 15, 2012 12:19 pm

Re: Sync problem @ high rpm

Post by j.oe »

Ahh forgot to answer the second question:

Low voltage threshold is set to 0V.

So i presume, the low voltage threshold should be set to -1.4V for example, because the sensor will reach this voltage for sure, ifit makes +1.4V as well ?
j.oe
Posts: 21
Joined: Sun Jul 15, 2012 12:19 pm

Re: Sync problem @ high rpm

Post by j.oe »

OK, now regarding the bottom curve, the noise exceeded the 1.4 V trigger threshold by 1.6 to 1.8 V before the "main" signal rised. That's why the error occured.
So i should try how to go for 1.6 to 2 V threshold. We'll see how much the sensor delivers at idle rpm. That must be more than the threshold anyway.
pavlo
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Re: Sync problem @ high rpm

Post by pavlo »

The thresholds are used by the ECU to set the state for the crank/phase sensor, if you are using a falling edge, then the high threshold level is the level that the ECu is looking for to set the state to "high" and then it will wait for the low threshold before setting it to "low", and the fall from high to low will be your falling edge.

So in your case you should look at raising the cam sensor threshold to say 2.5 volts to be above the noise, and then set the low threshold to say -0.5 to -1 to be well below the noise. You could try the filter on the cam, as that will kill the noise but it can mean that your threshold position will change with speed due to the decay of the voltage.

The other thing to keep in mind is that your run speed ( Breakpoints and Thresholds->Engine mode thresholds->Run mode engine speed threshold) will be the speed at which you switch from cranking threshold voltage to run threshold levels, and you need to have a high enough level at the low speed, which can be a problem with magnetic sensors. I would guess you'll be fine as you have very healthy levels at higher RPM.
pavlo
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Re: Sync problem @ high rpm

Post by pavlo »

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