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Discussion Starter #1
When I get back from the weekend I should have another (4th) BPC valve waiting for me and hopefully unlike the other 3 I bought from Ebay this should be working:roll: . However all is not lost as I now have enough parts from the others to put together a working one as well as some came with broken disks and others with broken electomagnets. I'm still curious as to it's true operation though - all the info I have read seems to indicate that the valve cycles the air pressure from the turbo outlet between the actuator and the intake. However with the hoses connected as Saab and everyone suggests this is not strictly true. The valve simply blocks and then unblocks the passage from the turbo pressure side - at no point is any pressure able to bleed to the intake from the turbo outlet. Thus the only 'cycling' is between either the turbo and the actuator or the actuator and the intake. Now if you swopped the actuator and turbo hoses round then this cycling would occur - it would bleed some of the air away from the actuator to the intake. Has anyone tried this configuration?
 

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I have, and there was no difference. If it's busted, then it's busted.
Also, Saab always had a problem with the BPC valve replacements. Sometimes replacing the BPC valve would fry the engine computer, and then replacing the ECM would fry the new BPC valve.
 

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Discussion Starter #3
I've been researching the ECU frying antics of the BPC on the Saabnet 9K BB - short circuit BCP fries the transistor in the ECU which in turn then fries the next BPC. I'll be testing the ECU next before I fit the BPC.
 

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The way the BPC valve is supposed to work is as follows:

With no interaction from the T5 software, the valve is open from the compressor port to the wastegate actuator, and closed to the intake port. The pressure is the same at the compressor port and the wastegate. (Same as when the BPC valve is unplugged)

When the ECU starts to modulate the pressure to the wastegate, the software sends a constant frequency, constant voltage, variable duty cycle signal to the BPC valve solenoid. The solenoid starts to open the port to the intake which bleeds off a variable amount of air. The air pressure at the wastegate is lowered proportionally by the amount of air being shunted to the intake.

Bottom line, the wastegate actuator is mechanical, it always opens the gate at the same pressure, but the ECU determines how high the compressor pressure has to get before the wastegate opens.
 

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Discussion Starter #5
Checked the BPC elecrical connection just now - infinite (well my Digital multimeter couldn't measure it) between each outer pin and ground. Also got a constant 3-4V between the center and both outer pins while the engine was running and warmed up which means that it's probably cycling and my meter is averaging. So I am presuming it's safe to fit another BPC valve.
 
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