Since there is a bit misleading/mis-presented information about how the dual vanos controls work here is a little explanation.
Dual vanos referes to dual solenoid control cam adjustment mechanism employed by BMW ///M , normal BMW engines run on a single solenoid for each cam.
Two readily available channels are required per camshaft. These need to be high side driven channels as the solenoids are grounded on their other input wire.
Output type : Dual (vanos)
Near PWM-ing period range :
This field refers to as how many degrees away from the target the solenoids will be operational
The PWM duty cycle is also proportional to the current distance away from the target.
This needs documenting as I was under the impression that PWM-ing would take place until the target and actual angle are within this period. However that is not the case.
Example :
60deg range
+10deg error
Duty cycle : 16% on one solenoid. 0% on the other solenoid.
60deg range
+20deg error
Duty cycle : 33% on one solenoid. 0% on the other solenoid.
60deg range
+30deg error
Duty cycle : 50% on one solenoid. 0% on the other solenoid.
Ultimately giving this table
Error Duty cycle
| 10 16% | | 20 33% | | 30 50% | | 40 66% | | 50 83% | | 60 100% |
DC% = Error / PWM Range
If the error is in the other direction same applies to the other solenoid.
So by halving the range so do you double the DC% at the same amount of error. This will effect the responsiveness of the system
To low of a range value and your system might become unresponsive completely as errors past the range will turn off both solenoids, rendering any control impossible (with time oil does leak from the control chambers and the cam might come back into range).
Improved setup would allow any range but turn this value into a P value (which it already is in effect) and clip the limit at the "range" value
i.e.
@60deg range with 70deg error it would still yield 100% duty cycle, not turn of the solenoid.
@60deg range and 30deg error you get 50%
@30deg range and 30deg error you get 100%
@30deg range and 70deg error you get 100% and so on .
Start off with lower values and see if you get alot of overshooting, raise to lessen overshooting.
PWM Period : 25-375Hz
This should be the same as the standard system as long as the standard system operates on the same principles of control as VEMS does.
Other systems might be pulsing both solenoids at different amounts to move the camshaft slowly or more smoothly.
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