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Old 10-23-2013, 11:40 PM   #1
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Default VVT stopped working

I am running stock VVT head, MS2/DIYPNP with VVTuner standalone box to control VVT.

I finished wiring it all up last night. With the "default" table values loaded, I fired it up, took a quick datalog to make sure the default PID values were reasonable and if it would track the target advance. Just idled and raised RPMs a bit to change the advance target to see how it'd do. Everything looked great.

Fast forward to today, I loaded on my own custom table, fired up the car and went for a drive. I drove around for a bit and noticed now my advance was stuck anywhere from 0 to about 6 degrees max, even though the solenoid would at times run full bore @ 80 duty cycle trying to hit targets.

I loaded up the "default" values to see if that would maybe fix something, but it was same story there, not surprisingly. Only thing else different about tonight would be the oil was hot, I guess? The OCV hums when it's plugged in, so I think wiring is fine (plus everything was peachy last night and I didn't touch anything).

Does this just sound like a bad OCV, that just happened to work for a few minutes before it decided to crap out on me? Here's 2 datalogs to capture what's going on. First one is last night when it worked fine, and second one is the one from tonight.. you can see it commanding ~30 degree advance, duty cycle ramping up, but no change in observed cam angle. Although not totally evident in the datalog, when duty cycle goes up, it does seem to advance the cam, but only like 2-3 degrees.



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Old 10-24-2013, 10:36 AM   #2
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So, started it up and idled/revved it up a little in the garage... Worked fine again with the engine cold. Not driving it to work today but next I need to fire it up cold, see it working, then go for a drive to see when it decides to stop working.
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Old 10-24-2013, 02:04 PM   #3
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Do you have an oil pressure gauge? My first thought is that you don't have sufficient oil pressure once it warms up to actuate the VVT.
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Old 10-24-2013, 02:31 PM   #4
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Yes, in cruise I have plenty more of oil pressure, 40+.
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Old 10-24-2013, 03:43 PM   #5
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Also, I have the BE street/strip oil pump, so it should be able to provide enough volume/flow.
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Old 10-24-2013, 05:28 PM   #6
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Weird. Yeah I'd diagnose it more before replacing the oil valve
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Old 10-24-2013, 10:30 PM   #7
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Still not working right.

Today I changed the oil (Rotella 5w40), reloaded the firmware onto the VVTuner, then went for a drive, datalogging the whole time. Oil temp was around 90F when I started and highest I think I saw towards the end was 205ish degrees. I was watching the VVTuner display and oil temp/pressure like a hawk to try and correlate something. Everything looked solid till around 160-170 F on the oil temp. Around then I noticed I would need above 2500rpm or so for the cam advance to get anything above a few degrees, but above 2500ish, it would work just fine. As the oil got hotter and hotter, that RPM "point" continued to climb. At around 190F, driving at 4k RPM it would not advance the cam at all, even though it would be targeting 20+ and OCV duty cycle would be 80%. I noticed though if I got into boost, at around 10psi (I brake boosted to keep RPM contant), it would spring to life, then once out of boost, cam advance would die off again. By the time oil temp got near 210 F, the cam would not advance no matter what.

I have a 20 minute datalog that I'm sure no one wants to look at, so really the gist is, as oil gets hotter/thinner it has a harder and harder time trying to advance the cam, and then eventually it just stops all together. Oil pressure was a hair higher too now that I'm running the 5w40 (was 10w30 conventional oil before).

I pulled the solenoid and checked it out- it looks fine, seems to move freely and it seemed to work fine... I could see the whole inside moving around to different positions depending on the commanded duty cycle.

I'm running out of ideas. At this point all I can think of to do is get another solenoid and test it out. If that doesn't work then I guess I will just have to press forward, VVT-less. Again, I have a "VVT compatible" oil pump. I do have the turbo feed and VVT sharing the oil port on the block (under intake mani), but I can't imagine the turbo is all that taxing, with the tiny little restrictor and stuff I run for a BB turbo.

Any ideas let me know!!!!
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Old 10-24-2013, 10:38 PM   #8
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Maybe the VVT actuator itself (in the cam gear) is FUBAR?
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