Bleeding of the hydraulic system VISCOMATIC 164 Q4

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alexeinik
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Bleeding of the hydraulic system VISCOMATIC 164 Q4

Post by alexeinik » Sat Mar 24, 2012 12:45 pm

Good day!
Decided to change the oil in all wheel drive system of alfa romeo 164Q4 for the Tutela GL/R (it was previously filled ATF). Now a am having a problem- how to remove the air from the system without having viscomatic Examiner ? Is there anybody here who produced this process without a tester? That is what written in describing of viscomatic system:

The exhaust of the circle is made by an appropriate valve inside the device, and is not thus not accessible and not adjustable.
The exhaust is to be accomplished only with ALFA ROMEO the TESTER: This procedure plans the start of the engine, whereby this is brought to 2000 revolutions; then sends a controlling of the tester a constant river of 450 mA to the proportional valve and controls according to also the memory load valve, increases the pressure of the circle over the maximum operating values, whereby the bleed valve is opened (on 102 bar calibrated) and lets to the container air collected in the plant to stream out. In the case of completion of this procedure it is possible to examine with the tester whether the plant without air is.
Of course, I can make the current source 450 mA, apply 12V to the memory load valve, but can it hurt anything?

164 TD
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Re: Exhaust of the hydraulic system VISCOMATIC 164 Q4

Post by 164 TD » Sat Mar 24, 2012 1:46 pm

Never put 12V on the proportional valve, it will burn the coil!

Without the Marellitester and the correct module, it will be hard to bleed the viscomatic system, but not impossible.

1) measure the resistance of the pressuresensor (with no pressure applied.) and make a dummy resistor with this resistance.
2) hook up the resistor to the wiring of the pressuresensor.
3)make sure all 4 wheels are free running and in the air.
4)start the engine while applying brakes for a few seconds( to let the viscocoupling engage) and rev it up to 1500 rpm.
Now the pressure in the system is only controlled by the RPM of the engine.(The pressuresensor is fooled) The recharge valve will remain open and the pressure will exceed the normal operating pressure.At about 102 bar the bleedvalve will open. To make sure there is a flow going on, vary a bit in rpm for the proportional valve to open end close (rear wheels try to keep up with front wheels)

In theory, this should work!


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alexeinik
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Re: Bleeding of the hydraulic system VISCOMATIC 164 Q4

Post by alexeinik » Sat Mar 24, 2012 2:27 pm

Thanks for the tip! Connect a resistor instead of the pressure sensor is a good idea, but why not simply apply 12 volts to the memory load valve? And it remains an open question with a flow contro valve.Viscomatic tester gives for bleeding constant river of 450 mA. Why 450 ma? And why the current to this valve varies by “Duty Cicle”, but no simply DC? I don't know what will be behaviour of flow control valve. May be in this case valve will be always closed and bleeding does not happen?

164 TD
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Re: Bleeding of the hydraulic system VISCOMATIC 164 Q4

Post by 164 TD » Sat Mar 24, 2012 5:12 pm

Not easy to explain how a duty cycle controlled valve works, but both the proportional valve and the idle actuator of the engine work that way.
Try to understand it as a steppermotor that can be adjusted to any position between open and close.

The technique is called Pulse-Width Modulation.(PWM) The coils resistance is very low and a 12V will draw a short circuit current.We tried to dodge this problem by using a controlled power supply and adjusting it to 12 V 450 mA. The voltage collapsed instandly. The pulses generate a "induced resistance" which keep the voltage up.

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alexeinik
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Re: Bleeding of the hydraulic system VISCOMATIC 164 Q4

Post by alexeinik » Sat Mar 24, 2012 5:53 pm

Thanks for the explanation, but I am understanding very well what is the PWM, because I am a radio engineer. Besides, i understand why in this case the manufacturer used the PWM, it because controller generates a digital signal, and it is easier to integrate it on the valve coil, than make installation DAC. The main question it is i am not quite understanding whether the control unit to send a control signal to the main flow valve, if it will accept a foolish signal that the system has no pressure? Maybe variant with a direct connection rechargeable valve more right and leave the pressure sensore continued to show the real pressure in the system?

164 TD
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Re: Bleeding of the hydraulic system VISCOMATIC 164 Q4

Post by 164 TD » Sat Mar 24, 2012 7:54 pm

Hydraulic group
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Proportional Valve
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Proportional Valve flow
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Rechargevalve
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