How Subaru’s Factory Boost Control System Works

[Christian.]

How Subaru's Factory Boost Control System Works v1.09
This document has been created to teach you how the factory boost control system works in all turbo-charged Subarus, 2002-2007. Information about how the vacuum lines are plumbed, where the "T" is located, how the individual components function, etc. are all covered in this document. I will be happy to answer any questions you may have.

Updated 04/02/2007 - We have revised the document to v1.06 and we have included some plumbing instructions for external wastegates and 3-port boost control solenoid valves.
Updated 04/17/2007 - We have revised the document to v1.08 and we have included some plumbing diagrams for various 2 and 3-port boost control solenoid valves. These diagrams should be very helpful when you are trying to figure out which vacuum lines go where
Updated 04/24/2007 - We have updated some of the diagrams to include more specific information on the 3-port EBCS solenoid valves, updated to v1.09.

Take care,
Christian.

[cubuff77]

This is the greated thread ever. Thanks Christain.

[mikeyd]

Ok so I just did Stage 1 93oct on my 05 LGT and peek boost seems to be closer to 18psi now (according to my gauge). This makes me nervous as the map notes claim ~15.

I havn't had a chance to verify the boost using the AccessPort but when stock my gauge read about 13 peak (which before it only seamed to hit in 5th gear btw). Is 13 acurate for stock and if so what the hell do I do about my current 18psi??

Despite my nerves right now I must say, awsome product so far. COBB kicks ***.

[iamchris]

Awesome write-up! Thanks very much!

However, it's "for all intents and purposes" and not "for all intensive purposes." You guys are very professional so I thought I'd clear that up

[kerpal]

Wow.. Thansk Christian

[subdoku]

Hello Christian ,

congratulations for your document !!

my subaru is not a wrx but a GT model year 1996.(we call it GM Great Mother in France !)

so the boost control system is different on my car : the wastegate solenoïd valve is a 3 ways valve and the restrictor pill is not located inside vacuum line 1 but inside vacuum line 4 !

so i don't know exactly how to modify my car to get more boost spike !!

my question : do you have a document with some explanations about boost control system for subaru impreza model year 1995-1996 ?
if you are not a specialist do you have a name of a contact ?

Thanks for your help.

René

[Charlie]

Hello Christian ,

congratulations for your document !!

my subaru is not a wrx but a GT model year 1996.(we call it GM Great Mother in France !)

so the boost control system is different on my car : the wastegate solenoïd valve is a 3 ways valve and the restrictor pill is not located inside vacuum line 1 but inside vacuum line 4 !

so i don't know exactly how to modify my car to get more boost spike !!

my question : do you have a document with some explanations about boost control system for subaru impreza model year 1995-1996 ?
if you are not a specialist do you have a name of a contact ?

Thanks for your help.

René

This forum is mostly for the USDM Subaru's, not world wide.

Christian "may" be able to answer your question, or you can try www.nasioc.com or other sites.

Oh, and "spike" is considered bad, very bad.

[williamsmith123]

Awesome write-up! Thanks very much!
However, it's "for all intents and purposes" and not "for all intensive purposes." You guys are very professional so I thought I'd clear that up

[ej22t]

Its a good write up and let me learn things new everyday, here is my question for my car:
I have be using my V2 91oct map for my 02 WRX for almost a month and along with the boost meter and it always showing that I could be maximum only around 12.6psi, not even reach to 13psi at all.
Some of the other APv2 user told me since my mod, and it could make the car not running max boost to around 14psi.
Currently , I have STi uppipe, EGT (deleted but use resistor), STi top mount intercooler, K&N stock air filter, HKS BOV.
As for some other user said that since I have the uppipe and intercooler, it makes the boost so low!
Can you tell me why the boost so low and are there any why to make it higher?
Thanks for reply
Ben

[STiKilla]

Just noticed an error as I was reading this document. On page 15 at the bottom where it talks about...

3-Port EBCS Internal Wastegate Set-up, Interrupt-type

It says that you need to connect a vacuum line from the compressor to the pressure inlet port on the EBCS (port 3 as per page 14)
Then it says that you can blow thru this port and that air will come out of one of the other two ports. However, next it says that you should attach a vacuum line from the port with air coming out to the INTAKE SYSTEM. This doesn't make any sense because when the EBCS is de-energized ports 3 & 2 allow air to flow between them so obviously you would need to have port 3 connected to the compressor and port 2 going to the wastegate. The way that it is described on page 15 would suggest that you need to hook port 3 to your compressor and port 2 to your intake which would cause the wastegate to never open which would obviously = FAIL

Just thought I would point that out because it had me scratching my head when I was reading it