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NG900 & OG9-3 Performance, Mods & Tuning Covers Tuning & Performance modifications for the NG900 (1994 to 1998) & OG9-3 (1999-2002) & '03 Convertible

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  #1  
Old 21st August 2005
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stromer stromer is offline
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Default sqr ecu installed, bad bpc?

I installed my stage 3.9 SQR ecu tonight. Everything with the car seemed great, ideled fine and everything. I took it for a drive and was only getting base boost of 6 psi. Now I have had a mbc on the car for the last 25k miles or so. But I switched back to the factory bpc with the ecu, as you're sopposed to. I have all the lines hooked up and everything. Now with the line to the wastegate unhooked, I was boosting fine, and very high, well about 6 psi. So that must mean a bad bpc, right?

So what do you think, bpc or not?

Anything else I can check?

Any particularly cheap places to pick up a bpc?

What if I have one of those ecu's that shorts bpc's? Should I give up now? Is it too early to tell?

Why can I not run a mbc with this ecu? What if I leave it at like 15-20 psi?

Thanks for all the help. As it is now, the car is back together still with the sqr ecu in, boosting 6 psi. But I know I'm safe anyways.

Last edited by stromer; 22nd August 2005 at 12:36 PM.
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  #2  
Old 22nd August 2005
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BLE 9-3se BLE 9-3se is offline
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Quote:
Originally Posted by stromer
I installed my stage 3.9 SQR ecu tonight. Everything with the car seemed great, ideled fine and everything. I took it for a drive and was only getting base boost of 6 psi. Now I have had a mbc on the car for the last 25k miles or so. But I switched back to the factory bpc with the ecu, as you're sopposed to. I have all the lines hooked up and everything. Now with the line to the wastegate unhooked, I was boosting fine, and very high, well about 6 psi. So that must mean a bad bpc, right?
> Welcome to my world. Base boost should be 7 lbs.
Quote:
Originally Posted by stromer
So what do you think, bpc or not?
> Possible. Do you have a friend who has one you could test on your car?
Quote:
Originally Posted by stromer
Anything else I can check?
> Look for vacuum leaks. MAP sensor? O2 sensor behind the cat? Get a tech II on it.
Quote:
Originally Posted by stromer
Any particularly cheap places to pick up a bpc?
> I don't think so... junkyard, but that might not be the best place to get a BPC.
Quote:
Originally Posted by stromer
What if I have one of those ecu's that shorts bpc's? Should I give up now? Is it too early to tell?
> You'd need to talk to Automotion about that.
Quote:
Originally Posted by stromer
Why can I not run a mbc with this ecu? What if I leave it at like 15-20 psi?
> The MBC takes control of boost away from the computer. When your computer was stock, it could handle this variation. Since it has been modified to adjust air/fuel mixtures, who knows how far out of whack an MBC would put that ratio? Better to be safe than to burn out a piston....
Quote:
Originally Posted by stromer
Thanks for all the help. As it is now, the car is back together still with the sqr ecu in, boosting 6 psi. But I know I'm safe anyways.
> Good luck man. I'll keep you posted on how things go on my end with my own worries.

Last edited by BLE 9-3se; 22nd August 2005 at 09:54 AM.
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  #3  
Old 22nd August 2005
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Blue, you mentioned the MAP and the second O2. If these were faulty, I'd get base boost? What if they were faulty with the mbc, would I ever have known? I mean I was pretty sure it was the bpc. Anything else that is possible is new to me. I'd rather not go to the dealer and have them put a tech II on it.

I know what you are saying about why not to use a mbc with the ecu in general. But if I keep the boost down to under 20, what would the effects be then? Would the same potential problems be there? This would only be for the short term as I look for a good bpc.
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Old 22nd August 2005
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Yeah, the MBC is still going to limit the boost to whatever you tell it to, ecu or whatever.
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  #5  
Old 22nd August 2005
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My 2nd O2 sensor is functioning okay, but since my cat isn't, the O2 sensor is sending weird readings to the ecu (as if the sensor were faulty) and the ecu is adjusting according to what it is being told, thereby reducing my boost.

Are you holding boost at all? Or is spiking and trickling off like mine was?

I really couldn't say what the effects would be, but that there is a great deal of risk of running very lean and having bad things happen to your engine. Everyone that I can think of whose opinion matters to me about tuned software and MBC's say that the two don't mix.

A family friend has a Saab piston on his desk at his shop that he split in half from running too lean during a race. It was a frightening ($$$) thing to see!

An hour's worth of tech II time should be $75. Might be worth it to ease your mind a little, or at least give you an idea of what's going on.

See if you can get together with MG_TD and borrow his BPC for a few runs. I bet if you gave him a beer he'd be happy to help you.

Like Jak would say, "it's a process of f*&$ing elimination."
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  #6  
Old 22nd August 2005
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Yeah, the process of ellimination....

Well MG has a t7, and so his bpc won't work on my t5 I don't think.

I guess I could go do the tech II. Just go in and say what? Here's my car, tell me why its only at base boost?

Right now the car does not go above 6-7 psi at all. There is no spike whatsoever. It runs very smooth up to this point and actually has considerable power considering.

I know what you're saying about the mbc and not mixing the ecu. I guess I'll call the dealer this afternoon.

I'm still hung up on the bpc. I did the test of disconnecting the wastegate line and then it boosted fine. From all I've read this is a positive indication of a bad bpc. Why would I look to anything else? From what I understand, another faulty part wouldn't put the car to base boost, but rather give sportadic boost. Something like what you had in your car when we went for that ride Blue.
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Old 22nd August 2005
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Perhaps there is something about ECU upgrades I don't understand. I realize that the fuel cut is removed but as long as you didn't go above some insane level, what would be the difference. I realize running lean is bad. As long as you have an accurate boost gauge though....


I don't think I'd run one anyway w/ an ECU. As long as the boost DID make it higher than the stock 9-10 psi and if they removed the 1st and 2nd restrictions...
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  #8  
Old 22nd August 2005
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I am running the MBC right now set to 22 psi with no knock or anything (93 octane gas,good plugs,etc. stage 4+ SQR) becuase my BPC crapped out a little while ago and haven't replaced it yet.I believe you have a bad BPC.Put the MBC on there,just set it to a low setting like 14 or 15 psi,you should be fine as long as your gas,plugs,etc. are in good shape.You have the jak stoll i/c so your air charge is very cool anyway.If the car boosts to this conservative setting,then you know the BPC is bad.It really couldn't be anything else.If you are really worried,then just take it for one run like this then convert it back afterwards,just to diagnose it.Eeuropartsa has BPC's for like $200,I don't know of any cheaper ones.
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  #9  
Old 22nd August 2005
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I called Paul at Automotion today for his input. We determined that in fact the bpc on the car now is gone bad. I'm picking up a new one tomorrow for $190 locally. What I'll do is pop this one in. Hopefully everything is well.

There is a chance though that the ecu will short out this bpc. There is a problem with some t5 ecu's as they do this. I'm pretty confident mine isn't bad as the person I bought it from had used it on his car and as Frank told me when he was tuning it, it actually had BSR software already on it. So hopefully all will be well. But if not, and the ecu has this problem, Paul can fix it. I guess Frank figured out a way to put in a resistor or transistor or something. I'm not too sure. That would cost me $100 for this repair on the ecu. As the bpc is warrantied for a year, I'll just go get a new one to go with the fixed ecu.

So if I have to send it to Paul, I'll just pop back in the stock tuned ecu (thank god I got a core, best $75 I spent!) with the mbc at 15 psi or so.

But Paul said he won't have the materials to fix the ecu's for a month or so. So until I send it I'll put the mbc back in a run it at 15-20 with the tuned ecu.

Thanks for your input Adam/A12. I trust ya man. Even if we didn't get to go for that ride in your car for proof, you seem like you know what you're doing when it comes to tuning your car. Lucky it was just a beer bottle you ran over and not the tailight to Paul's 9000!
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  #10  
Old 22nd August 2005
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sweet hopefully you'll get this all cleared up and be able to fully enjoy everything
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  #11  
Old 22nd August 2005
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Yeah, hopefully things will go smoothly. The biggest hindrange will be if I need to get the ecu fixed by Paul. I leave for college (car staying home) on the 28th. I won't be home for sure until Oct 9th. Then it'd be Thanksgiving after that. I'll probably bring the ecu with me so I can mail it from there if I have to.

Oh, and my buddy just picked up his third gen supra turbo today, so I'd like the car back up to snuff as soon as possible!!!

Last edited by stromer; 22nd August 2005 at 09:40 PM.
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  #12  
Old 29th August 2005
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seth, if you want to try mine before you spend ~200 on a new one, I have no problem shipping mine to you.


also, if you had SQR eliminate the rear 02 check, then you shouldn't have to worry about 02 sensors messing up the BCS.

clean yours, lube it, and if it doesn't work, I'll send you mine in a day or So
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  #13  
Old 29th August 2005
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Oh I guess I should have given an update. I put in the new bpc and the car ran great for three days. Now I'm at school and the car is parked at home for a month or so, so hopefully its good to go. Boost goes to 18 psi very easily and the car runs very smooth. Gas mileage is way up to 31 when I go easy. I attribute this to the fact that the o2 sensor CEL is no longer an issue thanks to the new loop set-up of the ecu.
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  #14  
Old 16th August 2007
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Background, hitting fuel cut off before full boost. APC is bypassed per PMI's instructions, still hits cut off under 70-80% throttle.

Dug up this old thread:
Quote:
But if not, and the ecu has this problem, Paul can fix it. I guess Frank figured out a way to put in a resistor or transistor or something.
A mechanic has diagnosed my ecu as having this issue(BPC shorted out the ecu). Does anyone have further information on this repair. If I could get a schematic, replacing a part or two on a circuit board wouldn't be a problem.

SD
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