Wastegate Modulator - testing and unpowered behaviour?

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Originally Posted by sierrafery

Hi Paul, You might not have misunderstood my post it's just that maybe we approach it differently. AFAIK with energised WGM it's not like in your second scheme but something like this

i mean that when the ignition is turned on the full flow from 1 to 3(from the de-energiseed status when actually boost is not present as the ignition is off) will be redirected entirely to port 2 and at that stage it's no comunication between 2 - 3, then as boost will start rising, at a point the WGM managed by the ECU will start splitting the boost from 1 between 2 and 3 ending up directing it all(not 100% though) to 3 at full load... but there is a stage where boost is present at lower load then port 3 is closed and all goes out through 2 to achieve better throttle response untill boost is high enough ... that's how i understand that but i dont insist it's correct

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I'll stick with what I posted.
I've verified that information with testing and it matches Pierburg service information and patent documents.

I'm not gonna contradict that just explain me please according to your second drawing do you mean that when the WGM is energised by starting the engine port 1 is completely closed and only 2 -3 are comunicating? ... if yes i can understand that and i stand corrected.

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Originally Posted by sierrafery

I'm not gonna contradict that just explain me please according to your second drawing do you mean that when the WGM is energised by starting the engine port 1 is completely closed and only 2 -3 are comunicating? ... if yes i can understand that and i stand corrected.

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Hi Fery,

A solenoid is energised by current flowing through the coil.

As I'm sure you know Current = Voltage / Resistance.
From the data sheet and measurements it's known the solenoid coil has about 28.3 ohm +/-1.5 ohm resistance.

Unpowered you have +ve = 0V, -ve = 0V, so 0V difference, 0V/28.3 = 0 amps.
Ignition on but no PWM +ve = 12V, -ve = 12V, again 0V difference, and 0V/28.3 = 0 amps.
(I can't confirm but it's likely the ECU has an internal pull up to supply V when -ve connection is not earthed).

In both cases the solenoid is de-energised, and the flow is port 1 <-> port 3.

With ignition on, and PWM completing earth path, +ve = 12V, -ve = 0V, so 12V difference. 12V/28.3 = 0.424amps,
In this case the solenoid is energised and the flow is switched from port 2 <-> port 3.

This is what the bitscope capture is showing. The reference lead is attached to 12V and the +ve terminal, the probe is attached to -ve / pin A21 of the ECU.
When the PWM completes the earth path the voltage drops on the -ve terminal, and the voltage difference across the WGM terminals increases to approx 12V. The solenoid energises and the WGM switches.

So starting the engine does not alter the flow. It remains port 1 <-> port 3.
Only when PWM completes the earth path does the flow switch to port 2 <-> port 3.

The operation of the WGM is basically:
With 0% PWM boost flows to the wastegate. At low boost and full boost the waste gate operates as normal. Port1 -> Port3
With mid-range boost where the wastegate can creep open the ECU sends a PWM signal to the WGM to enable pressure to be bled away from the waste gate actuator. Port3 <-> Port 2.

Because the WGM is rapidly switching the connection to the actuator on (3) between intake pressure (2) and boost pressure (1) the actuator sees a blended pressure which depends on PWM %.

cheers
Paul

Sir, i'm happy we had this discussion cos i've learned something again.... not about voltages/PWMs cos IMO i undertand that but i have to admit that i was wrong about the way the WGM works from the air flow point of view cos after the last post of mine i had some remorse and made just a simple test to prove myself that i'm right and surprise, i proved myself that i was wrong and you was right :), turned ignition on and used a bycicle pump on the hose which i unhooked from the intercooler(direct feed to port 1), and YES, your second pic is spot on and i apologise for contesting it, port 1 is closed with ignition on without engine running...which after a deeper thinking i realised that it's logical to be so.... i'll not erase the wrong theory from the previous post of mine to let it as a lesson for others to investigate more before making statements... anyway without this "debate" i could have died with a wrong conception in my head so i feel lucky anyway.... please forgive me for contesting your statements, i can just promise that from now on i'll investigate deeply before i'll doubt anytrhing you say
[wink11]

Quote:

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Originally Posted by sierrafery

Sir, i'm happy we had this discussion cos i've learned something again.... not about voltages/PWMs cos IMO i undertand that but i have to admit that i was wrong about the way the WGM works from the air flow point of view cos after the last post of mine i had some remorse and made just a simple test to prove myself that i'm right and surprise, i proved myself that i was wrong and you was right :), turned ignition on and used a bycicle pump on the hose which i unhooked from the intercooler(direct feed to port 1), and YES, your second pic is spot on and i apologise for contesting it, port 1 is closed with ignition on without engine running...which after a deeper thinking i reasised that it's logical to be so.... i'll not erase the wrong theory from the previous post of mine to let it as a lesson for others to investigate more before making statements... anyway without this "debate" i could have died with a wrong conception in my head so i feel lucky anyway.... please forgive me for contesting your statements, i can just promise that from now on i'll investigate deeply before i'll doubt anytrhing you say
[wink11]

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Don't apologise.
I don't accept things presented on the 'net without verifying for myself, and I wouldn't expect anyone to do otherwise.

Both pics are taken from the Pierburg service information and match the information in the 1994 Pierburg patent.

If you have a look at the patent there is a detailed cross sectional view of the switching valve.
Patent EP0633415A1 - Electromagnetic switch valve - Google Patentsuche


Attachment 123048


In the patent description "terminal duct 11" and "channel 11" is same as port 2, "channel 12" is port 1, and "channel 24" is port 3.

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Between central portion 17 and rotor core 7 having the one connecting channel 12, a spring 23 is clamped, by means of which the armature 9 is loaded against the valve seat 13 of the other terminal duct 11.The passageway 10 is connected to a third connecting channel 24.Depending on whether the solenoid coil is energized 3 or not, the connecting channel 11 is connected to the connecting channel 24 and connecting channel 12 closed, or of the connection channel 12 to the connecting channel 24 and the other is closed (as shown).

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Deciphering patent speak is always entertaining. But at least you know it's going to be precisely worded.

What the patent describes is basically same as the service information.

The armature has valve seats at points 13 and 14. When the coil is de-energised a spring presses the armature toward port 2, causing the valve seat to seal port 2.
When the coil is energised the armature is pulled toward port 1 and the valve seat 14 seals port 1.

It also makes clear the flow. With solenoid energised port 2 is connected to port 3 and port 1 is closed. With solenoid not energised, port 1 is connected to port 3, and port 2 is closed.

Anyway, this labouring the point. [smilebigeye]