I first observed the current waveform on the VVT solenoid as applied by the factory ECU, and cam and crank signals. I could only do it with the car in the garage. When the cam is retarded (idle), there is zero current. When I rev it, it applies ~0.5A. The frequency is around 500 Hz and the duty cycle ranges from from around 40 to 65%. The current ripple is around 20%.
It seems that the solenoid is controlled by current, and its position responds to average current (average over the duty cycle).
The factory ECU will occasionally "blip" the current to 1A (briefly, as in for less than 1 engine cycle (2 revolutions) - perhaps a 'D' term (D in PID). As idle settles down, it will also blip the current briefly - like it wants to advance the cam for a very short time as the idle settles.
So I observed the cam vs crank waveforms as I applied current to the VVT solenoid.
It appears that the control range of current is 0.4 to 0.6A. However there isn't a simple 1 to 1 correspondence between current and advance.
Firstly there is hysteresis. I need to raise current to nearly 0.6A for it to begin advancing, and I have to reduce it nearly 0.4A to begin retarding.
And, once it begins advancing at a given current, it appears to continue advancing until I back the current off. It happens too fast for me to catch with the knob on my power supply.
Someone posted a diagram of the guts of the VVT actuator and the solenoid. I couldn't find it. Maybe by analyzing it, it can shed some light on the behaviour I've observed.
At 0.5-0.52A the valve is in the "hold" position. Below that it retards and keeps retarding, and above that it advances and keeps advancing. Valve sticks a bit thus the hysteresis.
What's the timeline on this? I have to pull my motor soon to refesh for next season but I might be able to get something done before I do so, depending on timing.
VW 3.2L VR6
Intake cam vvt - 52deg sweep
Exhuast cam vvt - 11deg sweep
60-2 crank trigger
4pulse/rev odd cam trigger on each cam
Currently running it in waste spark/semi seq due to my cam wheel not being supported yet.
I have had good luck just on/off controlling them as both are mainly used for emissions.
In stock form they're both closed loop control using the actual cam angle and varying the duty cycle to the cam solenoids. Looking at the factory ecu when in controlled mode the duty cycle is pretty close to 50% most of the time so the amount of adjustment with the valve must be fairly small once the cam has moved into position.
Let me know what you might need and I'll get it asap. I'm putting one of these in another car over the winter on ms3/3x as well and can use that as a test bed after my car is taken down.
Anyway, keep me posted. This will be a nice next step for MS3.
Peter Florance wrote:Vanos count here?
prof315 wrote:Peter Florance wrote:Vanos count here?
Why not? It changes cam timing. Of course it comes in 2 flavors.....the early version (M50 series motors) which is on/off on the intake cam only and the newer full time PWM version that is on both cams. I have a friend who races BMWs and has done some testing/tuning on the newer version and says that BIG average power and torque gains can be found by playing with dual Vanos.
jsmcortina wrote:For any of the uneven cam wheels we need a timing diagram and ideally a "log crank and cam" composite log from TunerStudio.
Paul_VR6 wrote:Good info Jeff! I'll do cam/crank logs of my 6cyl with the vvt on and off to see what the story is there. I do know that the 3.6L V6 has a different trigger arrangement for some reason.
jsmcortina wrote:Requirements of testers
- already have MS3 and have a good running tune
- have an engine with VVT on it
- are using stock sensors / trigger wheels
- have time and patience
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