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Dual stage MBC help!

3260 Views 20 Replies 9 Participants Last post by  codycsk
Hi,
I just installed a new boost gauge on my 97 900 vert ( has the 99 9-3 engine).
I have a max PSI of only a dismal 5-PSI, so i bought a Dual stage MBC from Turbosmart. I'm hoping this will be the answer to bumping up my boost a bit.
Only problem is, I'm not to sure how much PSI I should bump it up to .
I've read a few forums that said 12 is fine. and then other that said 14-14.5.

I don't want anything to blow, so any help will be greatly appreciated.
Also, would an Anticipator be needed? if so could i use the one from smart performance in conjunction with my current dual stage boost controller?

Thanks!
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sounds like you wasted your money on MBC instead of fixing what is wrong with your car
send it back if you paid anything over $30

if you're only running 5psi, sounds like you're running base boost
make sure you have no vacuum/boost leaks
is your BPC plugged in?
is it connected the right way?
if both yes, then you need to replace it and go from there

EDIT:
the dual stage boost controllers i see from turbosmart are all over $200
you could fix your boost issue and get a Stage 1 tune (which is much better than an MBC) for that amount and still have money left over
 

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Discussion Starter · #3 ·
sounds like you wasted your money on MBC instead of fixing what is wrong with your car
send it back if you paid anything over $30

if you're only running 5psi, sounds like you're running base boost
make sure you have no vacuum/boost leaks
is your BPC plugged in?
is it connected the right way?
if both yes, then you need to replace it and go from there

EDIT:
the dual stage boost controllers i see from turbosmart are all over $200
you could fix your boost issue and get a Stage 1 tune (which is much better than an MBC) for that amount and still have money left over
Wouldn't running a MBC bypass the APC completely though? so buying a new APC would be futile... i already have the mbc installed so, i can't return it.

Im assuming nothing is wrong with my turbo.
 

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Wouldn't running a MBC bypass the APC completely though? so buying a new APC would be futile... i already have the mbc installed so, i can't return it.

Im assuming nothing is wrong with my turbo.
grkguys point is that something else is wrong if you were only getting 5psi without the MBC. It is much wiser to fix whatever is causing this than to cover it up with an MBC... Also, with a working apc and correct boost you can then add a tune and supporting hardware to get much more satisfying power out of the car without endangering it.
 

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Discussion Starter · #5 ·
grkguys point is that something else is wrong if you were only getting 5psi without the MBC. It is much wiser to fix whatever is causing this than to cover it up with an MBC... Also, with a working apc and correct boost you can then add a tune and supporting hardware to get much more satisfying power out of the car without endangering it.
I see...
Okay, so my first step would be to try and find out why i'm only boosting at 5psi.
First culprit would be the APC, if i'm correct in saying so?
any other things to look for?

Well seeing that i already have my MBC installed and there's absolutely no way of me returning it. I guess i either take a hit, remove the mbc.
Replace the APC and then go from there. My stock boost pressure should be around? 8-9?

I hate to sound like an ignorant *******, but I'm trying to way out all my possibilities of getting my saab pacing.
 

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Wouldn't running a MBC bypass the APC completely though? so buying a new APC would be futile... i already have the mbc installed so, i can't return it.

Im assuming nothing is wrong with my turbo.
Running an MBC bypasses the BPC, correct.
But in doing so you take away the ability of the ECU to pull back boost in case of knock.. In other words you could be running "safe" boost levels, but the engine could ping its as.s off and still ruin the engine. The ECU wont be able to do a thing.

I have a handful of good used BPC I wouldn't mind selling for a good deal.
and you could get a Stage1 tune for less than $100 and get better performance than from an MBC while still keeping the safety feature of the ECU actually controlling the engine


I see...
Okay, so my first step would be to try and find out why i'm only boosting at 5psi.
First culprit would be the APC, if i'm correct in saying so?
any other things to look for?

Well seeing that i already have my MBC installed and there's absolutely no way of me returning it. I guess i either take a hit, remove the mbc.
Replace the APC and then go from there. My stock boost pressure should be around? 8-9?

I hate to sound like an ignorant *******, but I'm trying to way out all my possibilities of getting my saab pacing.
check for boost leaks and test out to see if the BPC is working (let us know if you need help with this)


clean up the mbc kit and box it up and try and send it back... just bs and say it was never installed (worth a try)
 

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Discussion Starter · #7 ·
Checking for boost leaks?
Which lines would i have to look at?
BPV line?
throttel body line?
i cant think of any others because i dont know of any others.

How would i test the Bpc?

Thanks for the input!
 

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Discussion Starter · #8 ·
So my friends old man who happens to be a mechanic. He said my model is the low pressure turbo. and it should run between 5-6 psi.
I'm not sure how true this is.. is there a way to check wich engine model is on the car?
 

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So my friends old man who happens to be a mechanic. He said my model is the low pressure turbo. and it should run between 5-6 psi.
I'm not sure how true this is.. is there a way to check wich engine model is on the car?
There are no LPT's of that sort in the USA. All the T5's boosted about 11psi AFAIR to get 185HP.

1. Remove the MBC
2. Bypass the BPC - there are hundreds of posts here describing how
3. You should hit fuel cut off on WOT. If not, you have a wastegate stuck or a bad BOV.
4. If you hit fuel cut off, then you have a bad BPC. You can re-install your MBC or do what gryguy suggests and get a tune and a replacement BPC.
 

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Stupid question: Is the 1999 engine you swapped in a T7 or a T5 (since both variants were still produced in 1999)? I ask because your car is a 1997 so it started life as a T5 for sure. So, if you in fact swapped in a T7 engine, did you also swap in the T7 ECU and harness? I would assume yes as I don't know that the car would even run otherwise. On the other hand, maybe that is why it is stuck on base boost - maybe it is in limp home mode due an identity crisis (i.e. the ECU is extremely confused).
 

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Discussion Starter · #15 ·
Stupid question: Is the 1999 engine you swapped in a T7 or a T5 (since both variants were still produced in 1999)? I ask because your car is a 1997 so it started life as a T5 for sure. So, if you in fact swapped in a T7 engine, did you also swap in the T7 ECU and harness? I would assume yes as I don't know that the car would even run otherwise. On the other hand, maybe that is why it is stuck on base boost - maybe it is in limp home mode due an identity crisis (i.e. the ECU is extremely confused).
That's actually a brilliant question that I quite unfortunately don't have the answer to.
I bought the car that way. Is there a way of checking?
 

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Discussion Starter · #16 ·
There are no LPT's of that sort in the USA. All the T5's boosted about 11psi AFAIR to get 185HP.

1. Remove the MBC
2. Bypass the BPC - there are hundreds of posts here describing how
3. You should hit fuel cut off on WOT. If not, you have a wastegate stuck or a bad BOV.
4. If you hit fuel cut off, then you have a bad BPC. You can re-install your MBC of do what gryguy suggests and get a tune and a replacement BPC.
I'll do that first thing tomorrow.
 

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That's actually a brilliant question that I quite unfortunately don't have the answer to.
I bought the car that way. Is there a way of checking?
One of the more obvious differences is that t7 requires a MAF (Mass AirFlow Sensor) on the intake. So if it is t7 you should see some sort of sensor on the intake piping after the air filter. If the piping does not have a sensor that should mean it is t5.
 

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Running an MBC bypasses the BPC, correct.
But in doing so you take away the ability of the ECU to pull back boost in case of knock.. In other words you could be running "safe" boost levels, but the engine could ping its as.s off and still ruin the engine. The ECU wont be able to do a thing.


the engine will pull timing if it detects knock which wont be enough to completely remove from danger, but will let you know something isnt right, that is if you know how to feel your car.. not to go against you but i hated the way my apc operated. the one on my 900 operated like a MBC. the one on my 9-3 (still t5) was stupid. limited boost in 1st and 2nd gears. retarded! if you choose to run a MBC you should have the supporting monitoring equipment (boost gauge and wideband an autometer or aem, they are the most accurate. buy cheap get cheap.) stock boost is 10psi +- 2psi fuel cut is 14.5psi (until you get a tune)
 
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