1985-1998 [Subscribe to Daily Digest] |
usually wastegates do not cause a problem. The wastegate would have to be
physically stuck shut, that usually doesn't happen. More likely that one
of the elements that control the wastegate is malfunctioning.
The BPC valve is mounted to the top,drivers side of the radiator. It has 3
vacuum lines attached to it and an electrical connector. The electrical
connector eventually hooks up to Trionic ECU and is used to open/close the
valve, which then regulates pressure to the wastegate actuator.
One of the vacuum lines (labled C on the valve) is attached to the high-pressure
side of the turbo. Another line (labled R) is attached to the low pressure
side of the turbo. The third line (labled W) is attached to the wastegate
actuator.
The wastegate actuator consists of a spring attached to a rubber diaphram.
The spring normally keeps the wastegate shut. Turbo output pressure is
applied to the diaphram, through the BPC valve. When the turbo pressure
equals the spring pressure, the wastegate will open. The value of the pressure that causes the gate to open is refer to as base boost.
The BPC valve recieves inputs from the ECU to control boost.
The electrical signal causes the a vane inside of the BPC to modulate the
pressure to the wastegate actuator. If the ECU wants more boost, it will
allow the pressure in the line to the actuator to be lowered, by allowing
some low pressure from the R line, keeping the pressure on the diaphram below
the spring pressure and keeping the wastegate closed.
If it wants to reduce boost, it allows more high pressure from the C line
to reach the actuator and opening the wastegate.
The ECU actually commanding the valve hundreds of times per second to control boost.
Anyway, You want to check the middle line on the valve( labled W).
One way to check it is to remove the line from the valve and suck on it.
You should not be able to get any flow through the line. If you do get flow,
either the hose is bad, or the diaphram in the actuator is broken. Either
way, it could be a cause of you over-boost problem.
I probably gave you more info than you need or want. Hope it helps
Post your results.
jj
'95 Aero
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