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Extra Cam postion sensor pulses


zwhitebread

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I have been having an issue where my ecu is receiving extra cam pulses. Its on a link fury G4+ running a Subaru EZ36. I have replaced the sensors and i am still having the problem. I have shielded wiring running from the link to the sensor. It seems to mainly happen on the RH inlet sensor but occasionally happens on the LH inlet sensor. I have attached a short log that has an example of what is happening. Let me know if there is anything I can try or that I should look for to get this problem resolved.

 

Thanks

2-3-2021 test.llg

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Can you do me another trigger scope at about 3000rpm.  Your cam sensor signal is inverted compared to our simulated EZ36 pattern, which could potentially push the falling edge beyond the range it was designed to work in.  But I do know some other subaru cam sensors flip polarities just above idle speed so want to confirm if yours does or not before I make a suggestion.  Im not confident this is your issue but it is the only think that jumps out so far.

Does it always happen at about 6000RPM?  Only under load or can you cause it with just a free rev?

Also, not related, but suggest you update to the latest firmware, you have the weird CLL spike in that log which was fixed in the later firmware.  

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I think the only way you are going to get to the bottom of it is to get someone with a standalone scope to connect to that cam sensor and monitor the waveform when the error occurs.  Possibly a spike of electrical noise or similar causing the ecu to see an extra tooth where it isnt expected.

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I think potentially this noise could be your issue, anything above about 1.8V on a DI is going to be considerd a tooth.  

Its hard to guess where that noise is coming from though, there are way more spikes there than spark events so it doesnt look like it is related to ignition (there would only be 6 sparks per 3 cam teeth).  What RPM was that scope capture done at?

 

pN1W3Ka.png

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I see about 5 spikes every 20ms, so that works out to 250Hz.  Looking in your tune the only thing running at 250Hz is the 4 VVT outputs.  So it looks like possibly noise from the vvt solenoids is being inducted into the sensor signal somewhere.  

If you still have access to the scope could you try again but with the VVT lockout set to say 5000RPM (so the solenoids are off) and see if that noise is then gone.

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In the scope above with the VVT off your spikes are much smaller, less than 1V, and the spikes that are there appear to be spark related now.  

 

5 hours ago, zwhitebread said:

ok. here is the weird part, with the vvt not locked out the signal looks was better than yesterday.  It doesnt have the spikes like it did yesterday.

Maybe try moving the scope wires around, possibly originally they were running close to the vvt solenoids and picking up the noise?  

 

Im almost leaning towards it being a ground issue but hard to tell still.  How/where is the ecu grounded?  Are you using a modified factory loom or is it a custom loom?  

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The wiring loom is custom from the ecu to the engine plug, where it retains the factor engine plug. All the engine wiring run through this plug except for the cam sesnors, they all run directly from the ecu to their respective sensors using shielded cabling and no plugs/splices The engine loom has been modified to only use the wiring that is needed. All the Ecu grounds are running through this plug directly to the engine block. The engine block had a 000 wire running from it to the battery. 

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Yeah I agree, its looking like spark events in that latest scope.  Does it have resistor spark plugs?  Are the coils grounded to the heads?  Stock coils (ie not cheap clones)?

Would it be possibly to add a supressor to the power supply to the coils (one on each bank) or do they have supressors factory?  

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I think it is worth a shot, im still not confident those spikes are your issue but they have potential to be and dont see much else wrong so we might as well try to eliminate them.  Supressors are usually a 0.5-3uF, you may find one as a small square black box near the coils on many modern cars, sometimes on the back of an alternator, or you can use an old school "condensor" like you have on a points car.   

"UBZ111" is a common aftermarket one like below.  Some of the OEM ones are a bit nicer design with two pin connectors etc.

FSWsHu0.png

 

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