Stage 2 Target Boost Problem

[J-mez]

Trying to figure out why my car won't reach target boost for a Cobb Stage 2 flash. I originally had the regular stage 2 flashed and switched to the stage 2 HWG map becuase of this issue. According to Cobb it sounds like a mechanical problem, but i don't even know where to start looking. The turbo isn't making any strange sounds, the boost system lines are hooked up properly and can't hear any other sounds which would imply there's a boost leak. However when starting up yesterday it began to idle fairly low and was shaky, not sure if that could point toward the stock BPV, friend with BOV has a stall issue sometimes, or what. No other mods besides catless turboback exhaustI .


This is the email from cobb


It looks like you are only running wastegate spring pressure for boost. The boost number should definitely be higher than that. You can try unplugging the electrical connection on the boost control solenoid and see if it changes anything. If it doesn't, it may need to be replaced. Also you can disconnect the negative battery cable to reset the ECU to see if that changes anything. If it does then the issue may be that that car is knocking or not running correctly but the log does not indicate this. If it does not make a difference then there is a mechanical issue that is causing the low boost.[/font][/color]




Here's a link to the data log.

https://docs.google.com/file/d/0BxSP...it?usp=sharing

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[cmiovino]

Unfortunately, it can be a lot of things. For me, the stock BPV gasket ($5 part) was leaking and needed replaced. That helped my AF learning 1 values and I literally felt an increase in power and was finally hitting target boost.

It can be a leak coming from where the intercooler connects to the throttle body... or any of the Y-piping under it. The turbo inlet also it prone to cracking after a few years.

And finally, it can be some of the things Cobb suggests.

... basically, it can be a lot of different things.

[J-mez]

Another thing i was thinking, I had the boost controller system redone when my engine was rebuilt because i had a MBC on there before, and i don't know if they put a new brass restrictor bead in the vacuum, how would that affect things?

[Saskatchatoon]

If you don't have the restrictor in the vacuum line you will underboost. It should be at the compressor outlet before the t-fitting.

[J-mez]

Haven't checked on restrictor in vacuum line because friend of mine who works on Subies a lot said it would cause over boost without it, he thinks it's a leak somewhere in the system.

[Tarzan007]

My 2012 WRX was doing the same thing. I checked all of the hoses from the intercooler. Fortunately, It fixed the problem. One of the hose from the intercooler was loose when I was removing the intercooler. Good Luck...

[jebjkey]

Smaller restrictor pill = higher boost for same WDC (lower WDC for same boost)
Larger restrictor pill or removing it altogether = lower boost for same WDC (higher WDC for same boost)

3 port EBCS in interrupt mode = who cares about the restrictor pill because it is removed and not needed. This is one of the benefits of a 3 port EBCS over the 2 port EBCS bleed style stock setup.

[jebjkey]

Originally Posted by J-mez

Haven't checked on restrictor in vacuum line because friend of mine who works on Subies a lot said it would cause over boost without it, he thinks it's a leak somewhere in the system.

Forgot to mention, your friend has it backwards with regards to the restricor pill.

[J-mez]

Thanks for the input, so if i were to get the 3port i would just plug that to the ecu control wire and everything would be good? or would it require a tune?

[jebjkey]

A 3 port in interupt mode will require different WDC settings compared to the stock bleed setup. So, yes you will need to tune for it. You can do it yourself with ATR or get a protune. But the EBCS has nothing to do with your rough idle problem. So I would focus on finding whatever is causing that problem. But yes, it is a plug-n-play (except for the tune) if you buy one made for your model.

Also, any restrictor pill that is not stock size will require different WDC settings and therefore it would need to be tuned.

Check out Cobb's .pdf on the boost control system and see if your setup is correct, including the pill in the correct location. It can hard to determine the size of the pill, even if you have another of the same size to compare it to. The sizes are all very close and you really cannot tell with the naked eye.

Since you had your boost control system replaced, it is certainly possible that the wrong pill (or no pill) was used. A replacement pill is pretty cheap and you may want to think about getting a known size pill if you cannot track down the problem otherwise.

A rough idle could be a seperate problem or it could be releated. If it is related, then you have a vacuum leak somewhere in the hoses for the boost control system. You may not be able to see it without removing each hose in the boost control system and inspecting them completely. You can do a leak test, but I think removing the boost control hoses is easier. Be ready to replace any hose that shows signs of degredation / cracking. I would do this for the inspection of the boost control system I mentioned above.

Are you still experiencing the rough idle, or was it just that one time?

[J-mez]

It was just one time.

[J-mez]

Checked the Vaccuum lines last night, still unsure if the y shaped hose deal will make a difference rather than a T shaped one, but there was no restrictor bead in the tube, going by subaru today to get a new one, hopefully that fixes the problem

[J-mez]

Solved! just put the restrictor pill (or orifice as subaru calls it) and took it for a quick spin, much better boost, easily hit 14psi in 3rd , will run a data log later, but all is looking a lot better

[jebjkey]

There is no difference between a "Y" and a "T" for the hose connections.

Glad your car is running well now.