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T5 1999 9-3
I would hesitate to apply 12VDC to the BPC as it might fry. It is pulse width modulated and is basically an AC device. I cannot remember the voltages applied, but 12V might be way too much. (Some AC devices will overheat with DC as the coils AC impedance can be limiting and with DC the coil's basic resistance draws too much current.)
If the vent port is not flowing, the boost will suffer. Some have sucessfully cleared BPC problems by blowing out every which way with compressed air. +It would be good if you could borrow a known good BPC to know if the problem is with the BPC or not.+
Base boost can be adjusted via the WGA, or with a SMBC which is easier to work with. With your T5, a MBC+A is also an option for a failed BCP. But any MBC solution needs to have supporting intake and exhaust mods. Some have combined MBC's with HOT ECUs, but you are then getting into extremes of power where you loose the failsafe of the BPC lowering boost when something else goes wrong. With a stock T5 ECU, a MBC or MBC+A works very well and we have had no problems reported. At the boost levels of stage 3, the pressures will be quite high and then the system can't bail out to a lower pressure. With the stock T5, and a MBC or MBC+A the system copes with octane issues by enrichment and timeing changes. With stock it does the same and only when the system cannot otherwise cope, will it lower boost.
With the T7's (stock), the ECU will blow the #1 piston if the MAF is bad and it does not manage to reduce boost to avoid such a problem. This happens mostly to the Viggen and Aero engines... not often but still no excuse from an engine management point of view. So lowering boost via the BPC is not the total solution for the T7s. There is no history of such things with the T5s.
You replaced the ECU if I recall correctly. This does introduce the possibility of a problem with the ECU itself. A borrowed BPC would help with that aspect as well.
You could have a leak in the turbo system, could be the BPV as well or its VAC line. You could run with the BPC-WGA hose off and in a quiet traffic situation and a gentle throttle, see what boost you can achieve. See if you can get 1/2 way through the red. That would be around or a bit higher than you can get with a MBC+A. Refit hose ASAP. If you can't get the boost, then I would be checking for a damaged turbo hose. Also check hoses at APC valve. BPV diaphragm could be torn or otherwise useless. If you are boost capable, then you have a boost control problem which involves the BPC and ECU. A leaking WGA diaphragm or blocked hoses to the WGA or from the turbo's hose barb would create high boost. Check that the WG is actually closing, some seize in an open state (rare). You can grab the WG lever and move it. The spring is very strong. The heat shield probably needs to be removed to do that check. Try other things first.
, Tue, 6 Sep 2005 09:30:45
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