Cam signal problem. only when hot and only under 1300 rpm

[maxiice]

This would be the scenario, starting her up and letting her idle to drift temp. And at drift temp i stops, throws 10-15 cam signal errors on a row ant that kills the engine.

S80 on a v8 vith 8 tfsi coils.

Have tryed diffrent hall senders on cam and magnetic sensors, they all act the same

[Rob Stevens]

It could be interference in the cam signal, try using the 'cam tooth noise masking active' or just use a higher rpm to enable sequential turn on.

[stevieturbo]

Ideally you need to scope the signal to see if it is noisy or a good clean strong signal.

It would be nice to have the option of ignoring the cam signal once the engine is sync'd up as some ecu's do allow though

But a hall sensor should be fairly robust as far as noise and signal strength goes compared to magnetic.

Is this a DIY cam trigger or OEM ?

[Jon K]

Had a somewhat similar issue - not as predictable as yours sounds, but I'd get my car hot, and then it'd stall at a traffic light if idling. Cruising it was fine, but idling it had issues. My issue was the hall crank sensor I retrofitted - it didn't like my wheel or vice versa. I also had to set a window on the cam sensor or I'd get errors. All good now with VR crank and hall cam.

[stevieturbo]

Oh...and it would be nice to be able to adjust trigger voltage thresholds...instead of that aspect being beyond any users control.

It would help a lot with trigger issues ( and of course, confuse the hell out of a lot of people too )

[Jon K]

Oh...and it would be nice to be able to adjust trigger voltage thresholds...instead of that aspect being beyond any users control.

It would help a lot with trigger issues ( and of course, confuse the hell out of a lot of people too )

Eh I am ok with the way it is. If you had voltage thresholds it'd be really hard to adjust properly and it'd need a ton of configuration. For instance, imagine a really lumpy cam'd 4 cylinder and a magnetic sensor - the voltage would be all over the place. Right now, its more of a self-adjusting logic which is fine. With a hall sensor its easier to account for the voltage as its an open/close signal, but a VR sensor can have huge voltage swings based on velocity of the trigger passing the sensor. Could be cool, could also be a headache.

[stevieturbo]

Oh...and it would be nice to be able to adjust trigger voltage thresholds...instead of that aspect being beyond any users control.

It would help a lot with trigger issues ( and of course, confuse the hell out of a lot of people too )

Eh I am ok with the way it is. If you had voltage thresholds it'd be really hard to adjust properly and it'd need a ton of configuration. For instance, imagine a really lumpy cam'd 4 cylinder and a magnetic sensor - the voltage would be all over the place. Right now, its more of a self-adjusting logic which is fine. With a hall sensor its easier to account for the voltage as its an open/close signal, but a VR sensor can have huge voltage swings based on velocity of the trigger passing the sensor. Could be cool, could also be a headache.

It's very very easy to set them up. Yes VR will see voltage changes, but you determine a threshold which is high enough to avoid noise causing a false signal, but low enough to accommodate rpm changes so all edges you are using are seen and recognised

In reality this will vary between 0-3v in almost all cases anyway, so it isnt a big deal. Just scope it and see where the voltages are ( a proper scope feature would show this )

Most other ecu's allow you to set trigger thresholds, and it really can help diagnose/resolve a lot of trigger setup issues.

Some will offer an rpm based table, others just a cranking threshold and engine running threshold.
RPM based does make more sense, even that in most cases will have the same values everywhere except 0-500rpm or so anyway unless it was a particularly troublesome car.

[Jon K]

Stevie I don't have a scope readout available right now but on my BMW the VR signal varies GREATLY, way way way way more than 0-3v. The signal is in AC current and is like 30 - 90v or something.

[stevieturbo]

Stevie I don't have a scope readout available right now but on my BMW the VR signal varies GREATLY, way way way way more than 0-3v. The signal is in AC current and is like 30 - 90v or something.

Exactly....when running it is always peaking over 3v...

So any variations above that dont matter.


As long as the signal rises above 3v, then falls below the zero line, ie falling edge triggered then it will be a valid trigger.

At cranking speeds, the voltage might only peak around say 1v, hence at cranking speeds you might set the threshold to 0.5v.

So as long as it goes above 0.5v and falls through the zero line it is a valid trigger.

So when running even if you had a very noisy trigger with random noise peaking at 2v, 2.5v, these would be ignored if you set the threshold to 3v.
If there was noise as high as 5v, but your peaks were as you say 30, 40, 50v etc, even setting a threshold at 10v wouldnt pose any issues, although if you had that much noise you have problems that need resolved.

[maxiice]

Problem was a faulty 0-5v oil pressure sender, shorting and killing most of the 5v signal to the cam sensor

Thanks for all inputs