SaabCentral Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
115 Posts
Discussion Starter #1
When i bought my 9-3 Aero about 6 months ago, it was on base boost. Did a quick test, removed the wastegate hose (from the BPC) and it boosted like crazy (as it should). Tested the BPC with a multimeter, it was showing 0 - ordered a new one, replaced it, boost was back to normal. The new BPC i got was brand new, OEM quality (bosch i think).


A few weeks ago, i started to feel like i don't have too much power - put my obd reader on it, boost wasn't going past 6 psi / 0.4 bar, so back to base boost again. Yesterday, i removed (again) the hose from the wastegate and it boosted like it should, hit fuelcut... So it seems the BPC is dead again.


What could be causing this, is it normal for the BPC to fail like this (less than 1000 km). Could something else kill it?
Or maybe i have a problem somewhere else?


Also, sometimes when i do a WOT pull (or almost WOT) - my charge air pipe pops from the throttle body, happened 3 times so far (about 10-15% of the times i hit it hard). The hose clamp was screwed tight every time, but i find it a bit loose...
 

·
Registered
Joined
·
7,094 Posts
Disconnecting the hose doesn't tell you whether the BPC is bad, it just tells you that boost is being cut. Could be from a bad BPC, but could also be the ECM cutting boost pressure due to detonation or problem with torque management. You really need a Tech 2 to monitor the ECM and determine whether the BPC is acting as its told, or if it's actually failed (which is unlikely). Often times, low boost is a result of a bad MAF.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #3
Disconnecting the hose doesn't tell you whether the BPC is bad, it just tells you that boost is being cut. Could be from a bad BPC, but could also be the ECM cutting boost pressure due to detonation or problem with torque management. You really need a Tech 2 to monitor the ECM and determine whether the BPC is acting as its told, or if it's actually failed (which is unlikely). Often times, low boost is a result of a bad MAF.



MAF has been cleaned about 2 months ago, but i didn't know this about the BPC. Previous BPC (the one i replaced with the current one) was toast. Going to measure the current one and see if it's working as it should.
 

·
Registered
Joined
·
18,376 Posts
MAF has been cleaned about 2 months ago, but i didn't know this about the BPC. Previous BPC (the one i replaced with the current one) was toast. Going to measure the current one and see if it's working as it should.

BPC runs on an A/C signal. Don't apply 12v to test.

There is an issue where the MOSFETs sometimes burn out in the ECU, but I never heard of them frying a BPC.

Jvan might be on the right train... the ECU might be doing something to cut boost. The wastegate test tells you that the turbo and wastegate work, but it doesn't tell you anything about the other side of the equation (one sided logical test).

My thought though is that if the BPC change seemed to cure it, then you did something by replacement that temporarily fixed the issue. Try disconnecting the battery cable, step on the brake to discharge the system, then reconnect. See what happens with the ECU reset.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #6
BPC is fine, tested it and it shows 7 ohms. Also tested by blowing air into it and it works as it should.


will try resetting the ECU and will also check the wastegate see if it's sticking or something...
 

·
Registered
Joined
·
88 Posts
If wastegate was sticking you wouldn’t reach fuel cut while doing the hose off-test.

Either ECM torque limiter or bpc I’d say
 

·
Registered
Joined
·
18,376 Posts
It uses a DC PWM signal, applying DC voltage to it wont hurt it but wont it wont pulse it back and forth.

Yes, that's more accurate than me saying it's A/C. It's on-off, high-low. But, we had one tester here burn out a BPC by applying non-stop +12v to his BPC. I don't know of anyone who did any followup testing of that concept.
 

·
Registered
Joined
·
115 Posts
Discussion Starter #11
i tested the bpc without current on it, tested it's resistance, 7 ohms as the wis indicates. also tried resetting the ecu, no progress there, boost is still the same.


i didn't try the bolt mod yet, or bypassing the boost valve on the firewall - will try them today (or this weekend).


also, the only thing i remember fiddling with is the charge air pipe - but it's back on properly. the only thing i'm not 100% sure to have a perfect seal is the pipe that goes from the cobra to the bypass valve - i know it has an o-ring and it hasn't been replaced. maybe i could be sucking air though there?


does anyone know the exact size of the o-ring?
 

·
Registered
Joined
·
18,376 Posts
If you passed the W hose test then you don’t need to check the firewall valve. It is there to limit the pull off action of the diverter/ blow off valve. But if you got full boost with W off then your blow off valve is working fine. The firewall valve isn’t the issue.
 
1 - 12 of 12 Posts
Top