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Spikes/Noise on VVT angle at high RPM (RB26 w/HKS V-CAM)


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Retuning a GTR R32 on a dyno after some upgrades. Also upgraded to the latest firmware when beginning the tune.

I am getting some crazy spikes in VVT angles at high RPMs in most of my runs (happens like 80% of the time) at varying severity which I did not notice in my previous tune. I doubt it is the actual angle and its just simply noise in the cam position signal. The VVT Error counter sometimes will increase as this happens.

Since the HKS wiring for the cam angle sensor was not shielded, I replaced it with a shielded cable with the shielding properly grounded on the ECU end but seems like it made no difference. Might actually made it a little worse but I am not sure. Playing around with the filter settings had not consistent effect either.

Attached are screenshots of a few of my runs along with my current VVT settings. I think the spikes in the duty cycle is due to the derivative kicking in as the angle of the cam "falls" sharply back down rather than what is causing the spikes in cam angle right? Should I do a log with a higher frequency? The car is now off the dyno though so will have to do a pull on the street.

Thank you very much.




Edited by MGV101
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What trigger mode are you using?  Can you do a trigger scope at idle and one at say 3000RPM initially, I might get you to do one at higher rpm later once I have some more info.  Do you have a standalone oscilloscope or know anyone with one?  

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Hello Adam, it's running on a multi tooth setup with a 12 tooth crank trigger on the crank and a single teeth cam on the exhaust cam.

Attached are the trigger scope at idle, a little over 3K and at roughly 5K.

Both triggers are using rising edge right now but after taking a closer look at the trigger scope, the two edges are kindna close to each other but probably not enough to overlap and cause any problems yet and I don't see any trigger errors after starting the engine. However, I think I would definetely want to switch the trigger 2 to a falling edge for better separation.

I don't have an oscilloscope YET but is strongly considering getting one. I really don't trust those super cheap no name brands but getting anything from a reputable brand is very expensive.


idle.llgx 5k.llgx 3k.llgx

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I dont think the knock excition will be related.  It looks like the cam input is seeing extra pulses for some reason.  This is really going to need a proper scope to see what is going on, it may just be a noise issue or it could be something random like a bump or void in the cam casting or similar.


On 1/28/2023 at 2:47 AM, MGV101 said:

I don't have an oscilloscope YET but is strongly considering getting one. I really don't trust those super cheap no name brands but getting anything from a reputable brand is very expensive.

A picoscope 2204A can be had for ~USD150, these are very good and probably the best option around that money.  If you want something cheaper then the Owon VDS1022 is about the best option.  Avoid the cheap Hanteks, they have no capture memory and the triggering sucks.  As well as the scope, for automotive testing you will want a few accessories, the Hantek accesories are reasonably priced and easy to get.  Here is my suggestion that will give you a good useful diagnostic tool:

  1. At least one 20:1 attenuator (HT201), you need this to reduce the high voltage spike that you get when testing something like an injector or primary ign down to a level that a scope can handle.  
  2. Two BNC to banana leads.  There are automotive specific ones like HT30A which are handy due to the 3M length.  Or you can get generic 1M length ones that will still do the job for a bit cheaper.
  3. A set of backprobes.  Something like HT307, get the thin pin like ones not the threaded ones.
  4. At least two banana alligator clips. A couple of different sizes is good, you want something that will clip on a battery terminal and maybe something that can clip on a small wire or connector terminal.  I have a couple of HT18A and something like P2007.
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Wow, those PC/USB based oscilloscopes are much cheaper than I thought.

I was mainly looking at standalone handhelds which costs multiple times more even for the most basic models if they were from any reputable brands.

For just ~$150 this is a no brainer for me and I could probably afford all the accessories listed too.


Ok, I've just looked up from amazon and I could get the 220A, HT201 and HT30A easily there. For the back probes and alligator clips, I couldn't see any recognisable brands listed on amazon so I just opted to get this set which should be sufficient to get me started. https://www.amazon.com/Testeronics-Multimeter-Extension-Connectors-Multi-Type/dp/B08QZRDY52/


Thank you for all the advice Adam!

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MGV101 , I tuned a few RB with V cam and Link G4+/X, I had this issue before I wonder if you could try these set up/PIDS




Your PWM Output will be different , this car also had 12 tooth trigger on the crank (PRP) with no missing tooth , running a modified NZ Trigger Home trigger wheel.

Have you measured the air gap on the cam position sensor , cam cover retainers stock Nissan Items? tightened to bottom out on the cylinder head?

If you zero the cam control map do you still get the cam position output jumping around?



any questions fire away, good luck


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Thank you for sharing Abbey and sorry for the late reply.

Since the car is off the dyno and I have no way to do tests safely and consistently on the street so I have not done any more testing yet to apply and try any of the new settings.

You made a very good point though. Knowing who installed the cam position sensor, I am 100% sure they have never checked the air gap and I will definitely check that out. I am not exactly sure what you are referring to for the cam cover retainers though.

Also looking at the settings you shared, is there any specific reason to use 0% as the base duty cycle? I guess the significantly higher (comparatively speaking) integral gain would help to home in the base duty cycle in CL, but wouldn't setting it to around where the cams would start advancing make the CL system work less? I know the duty varies a little sometimes depending on oil temp, pressure etc, but having it close to where it should be should help.

Thank you!

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  • 2 weeks later...

Hello Adam, everything came in and I am impressed with the 2204A. After more digging in on how to use the oscilloscope, I've realized it has MUCH MORE use than I initially expect.

Anyway, here are the wave forms I have recorded on the V-CAM sensor at idle and free revving at around 4000-5000 rpm. The signal looks perfect to me though and I really could not see any fault. I probably should have recorded the trigger 2 sync at the same time but I was too excited with the new oscilloscope and was too rushed to think of that.

Do note that I have used the 20x attenuator for the 4000-5000 rpm waveform but have not set the probe to 20x in the software so the actual voltage should be 20x higher. Actually, the 20+V @4500 rpm looks pretty high to me. Could too higher of a voltage cause problems with the reading? I imagine it would be even higher at 6-7K rpm where I am having my issues.


Idle 880.psdata 4500 20-1.psdata

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4 hours ago, MGV101 said:

I probably should have recorded the trigger 2 sync at the same time but I was too excited with the new oscilloscope and was too rushed to think of that.

Yeah it would be good to get trigger 2 in there as a reference.  

Also, have a watch of this video to learn about the pico streaming mode.  In streaming mode you can capture 2000000 samples Vs only 8000 in block mode.  This is enabled by setting the time base to 200ms/div (or longer), this means you wont be able to see the live waveform well on screen since you will be "zoomed" way out but if you set the sample rate high it will still be captured at high resolution so you can zoom in to see good detail afterwards.  The benefit of this is you can do much longer captures when an issue is only intermittent.  https://www.youtube.com/watch?v=_-WJ1akaVCw


Im pretty sure the high voltage shouldnt be an issue. 

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