TEXAS HEAT
Well-Known Member
Most likely 12v if this is like a N20 solenoid.I've been running the BOV for about 4 days now. Got it completed Saturday evening along with the Levels FMIC. But i've run into an anomaly which I am trying to sort out the cause of.
Under light load conditions, while cruising at a relatively constant speed, some times the BOV will remain open continuously. It's loud enough that I can hear it easily with the windows rolled down. It will remain open even as I give it more throttle for a short period of time, which becomes very obvious as there's little response form the engine and the vented air becomes even more audible. I cannot reproduce this occurrence on demand, but the last occurrence (yesterday) I noticed there was no boost or vacuum (bouncing around the 0 mark) while the issue occurred, which coincides with the fact that the valve is open, hence why the pressure gauge is reporting atmosphere instead of vacuum or boost.
Some possible causes:
1. Solenoid valve in the control manifold is sticking
2. BOV plunger is sticking
3. PCM software has a bug, possibly too much hysteresis, causing the valve to open, but the lower trip point to close it set too low, thus we're operating in the dead band of the hysteresis bounds and hence the valve remains open so long as the conditions don't vary significantly from the initial occurrence which caused it to open.
4. PCM software is functioning as intended and this is a design oversight on the part of Boomba. It is possible that the PCM may be holding the valve open by intent in these conditions to bypass the turbo while under very light load for fuel economy purposes, if the turbo isn't spooling enough to produce boost, it serves only as a restriction on an engine operating in the NA region (pressure at the throttle body is a vacuum, not under pressure when the turbo being driven fast enough to generate boost). The bypass tube between the compressor inlet and outlet is large enough to support adequate flow at low loads.
At this point in time I have not had much time to diagnose the cause of the issue, but have only become aware of it. Cause number 4 seems to be the least likely, but I have no proof of the factory PCM software's architecture to rule it out completely. I also have less visibility of the factory DV operation as it's not audible and I'm now aware of any PID's that monitor the BOV state. It may be a blind output, meaning the PCM drives the valve but has no visibility of it's actual state and operates by assumption that the valve is actually in the position commanded. The PCM software would certainly be aware of when it has commanded the valve to be in a particular position, but the valve may not actually be in that position.
The most likely would be causes 1 or 2, which I may be able to resolve by having Boomba replace the components or at the very least assist in diagnosing the issue. I would like to first test the vacuum operation of the valve by using a negative pressure sources to manually drive the plunger. I can use a manual air pump to test the pressure required to force it to return if it does not return under atmospheric (which it should due to the return spring). The valve should remain closed under atmospheric and under boost as the holding strength is still the spring rate (the turbo outlet pressure has a net 0 effect on the BOV plunger as the plunger is held shut by the same pressure, thus the mechanical spring in all instance is the holding closed pressure).
The Solenoid might be a bit more tricky, but I'm sure I can come up with an appropriate supply voltage to operate the mac valve. BTW, anybody know the operating voltage of the MAC solenoid? It would most likely be 5V or 12V, I could test 5V first, if no operation then 12 would be appropriate.
The factory ECU does see this value directly as (1) BPV Mode – Bypass valve mode. (0=Closed, 1=Open).
The only way I can see to determine what capacity the ECU controls this is to datalog under what conditions it is opened and/or closed.
I thought this might be an issue with the Boomba BPV if the ECU is commanding it to open based on a predetermined condition and it is not opening and/or vice versa.
My thoughts are possibly a bad solenoid. You can test it by hooking it up to your battery at 12v and watch the actuation of the solenoid itself to determine if it's working properly. Check all electrical connections, did you disrupt any grounds during install?
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