2002 BH5 Secondary not Boosting

[crazymf]

Well this has been a fun exercise to say the least

The problem we have is when you drive off from idle the primary turbo only boosts about 5psi, then when the secondary is supposed to kick in the boost drops to 0psi and thats it through the rest of the rev range.

Now i know everyone is thinking that i have a seized secondary turbo...We have done alot of diagnosing and part swapping with a known good vehicle.

Heres whats been done so far.

- Both turbos have been checked - Everythings fine there

- The ECU has been put into non boosting car from a boosting car - Didn't change a thing

- ECU from non boosting car put into boosting car - Boosting car still boosting

- Vacuum control box, same scenario as ECU - No change to either vehicle

- Exhaust shut off valve before secondary turbo removed and inspected - Perfect condition

- Cam timing checked - Perfect

- Airflow meter fitted from boosting car - No change

- Catalytic convertors checked - Not blocked

- Secondary intake shut off valve in intercooler checked - Working fine

- Vacuum hose configuration checked - All hoses go to where they should be

- Map sensor changed - No change

- BOV's checked - Perfect order

- Scanned for fault codes - No codes present, but when driving and watching what everything is doing on the select monitor, the knock retard is actually advancing the timing 9 degrees and the engine is pinking its nuts off

- Vacuum canister holds vacuum

Any help on this issue would be greatly appreciated. But we wont be giving up, a solution will be realised sooner or later, lol.

[Guest]

Carefull, Selct Monitor readout is differnet for some TB models

Which dealer do you work for?

Knocking retard , knock correction meanings are different

+9 deg can be timing advanced or can be retarding +9 deg

If the engine is detonating then the sensor wont be advancing the timing !

Anyway looks like you have "carpet bombed" the diagnosis and still not found the real fault

Many items you have missed that are some of the first checks you should have done are

........................................................................................? FAIRLY SURE I KNOW YOUR FAULT CAUSE BUT.....

If you are from a dealer then I suggest you contact me via PM

[crazymf]

Not from a subaru deal, from a small private subaru workshop.

Ah, yeah knocking corecction, +9 degrees which is advance, its not detonating, its pinking, there is a difference as im sure you are aware of.

We have pretty much checked everything for its operation and signal output against a known good vehicle and all the sensors are all working fine, only one we haven't checked yet is the primary boost controller, which will be done very soon.

Another thing, on the select monitor, we graphed the primary and secondary boost control maps, the secondary is starting to operate before the primary. On the good vehicle the primary is coming on 1st then followed by the secondary, so now we have distinguished the operation, all we need to do now is find whats causing the problem.

[Guest keltik]

broken vacuum line to the exhaust control valve?

[Guest]

knock sensor can not differentiate between pinking and detonating

What makes you so sure it's pinking?

Boost will be cut if knocking unable to be controlled by ECU

[EJ20T]

sure its not somethine simple like the primary BOV signal hose cracked? normal on these things

[EJ20T]

As stated above you have missed alot of the simple things, it sounds to me like the ECV is working and the intake control valve. Id be looking at the vac hosing, and the primary BOV and boost hosing under the ic. from what you say its leaking or re circing boost on the primary and then when the 2ndry comes on line theres not enough air flow to build boost. or the only other plauseable problem is the primary turbo wastegate stuck open

[crazymf]

All mechanical components have been checked and all are working, all vacuum hoses have been checked and none of them have leaks and all go to where they should.

[Guest]

 crazymf']

All mechanical components have been checked and all are working, all vacuum hoses have been checked and none of them have leaks and all go to where they should.

Well maybe it's not mechanical fault

I suggested earlier to PM me

[quote name='Ichi Ban said:

knock sensor can not differentiate between pinking and detonating

What makes you so sure it's pinking?

Boost will be cut if knocking unable to be controlled by ECU

[D-Style]

You havnt replaced any hoses or added any boost gauges etc etc.

I broke a t-peice on one of my vac hoses, replace it with other and was off. but the hoses and tee was bigger diameter and the BOV started to open after 5psi would even hit secodary. Went to local wreaker, found the tee and other factory hoses, replaced, and the car drove all good.

just another thing to look out for....

[crazymf]

Just an update - we have attained normal primary boost levels now by re-hosing the main BOV. Feeding it more boost to help keep it closed. Now getting 12-15psi. Problem is we are only getting 5psi of secondary boost. We have another exact same car and that has 10psi of secondary boost. Now just gotta figure out how to achieve that...

[Guest]

Not being rude or anything but you seem to be treading in unchartered waters if you know what I mean

Changing the factory set up on a factory car to fix a problem is going to cause problems

I have offered help via PM if you needed

15psi is way to much boost for a primary turbo, wont be suprised if one of you next posts mentions a blown primary turbo

[Guest]

isnt around 1bar standard boost for a tt b4 primary

[Guest]

14lb on secondary is normal

12lb on primary is normal

[dumbskate]

 Ichi Ban said:

Not being rude or anything but you seem to be treading in unchartered waters if you know what I mean

Changing the factory set up on a factory car to fix a problem is going to cause problems

I have offered help via PM if you needed

15psi is way to much boost for a primary turbo, wont be surprised if one of you next posts mentions a blown primary turbo

Yeah as a TT owner myself, i don't think I would want to turn up to pick up my car from this particular "small private Subaru workshop" and be told "well we have no idea what actually broke but we have made up our own way of putting your beloved car back together and fingers crossed its as good as the way Subaru's best brains had it in the first place".

for a professional workshop, it all sounds a bet too "number 8" for my liking.

[crazymf]

Well just to clear things up, and it does seem that you guys have your wires crossed. But we actually have another exact same car thats unmodified and working as subaru intended it too.

We have mapped exactly what everything is doing, when boost/vacuum is being sent to various actuators etc. And guess what, the working car is boosting 15psi on the primary. So before you go strangling me with the no8 wire i suggest you go and do some homework 1st.

Remember this is a 2002 tt legacy, they differ slightly from the earlier ones. The early ones boosted around 10psi on the primary and around 15psi on the secondary.

If you knew how much time we have spent on this trying to figure it out then you might have a better understanding. And the fact that its my bosses car must also have some credit.

So we still have the problem of only 5psi of boost on the secondary. Forget about the primary, I'm happy with that, as its working like all the other cars we've compared it too of that model year.

[Guest keltik]

Insufficient oil flow to secondary?

Theres not a lot left you can check unless one of your original checks was wrong

[crazymf]

Insufficient oil flow would cause a turbo too seize, not slow down

[Guest]

 keltik said:

Theres not a lot left you can check unless one of your original checks was wrong

That's exactly what i think too

Back to basic's time

Sounds like not enough exhaust flow to build boost during SECONDARY operation

= not enough heat being made by the engine, retatrded timing (knock fault) or incorrect fuel

= low compression (possible bent rod) , or cambelt timimg etc

[Guest]

 crazymf said:

So we still have the problem of only 5psi of boost on the secondary. Forget about the primary, I'm happy with that, as its working like all the other cars we've compared it too of that model year.

Boost is controlled by the primary turbo actuator / solenoid and ecu

5 psi isnt even wastegate opening pressure with is just over 7psi

Hence my suggestion of not enough heat to build boost with

Also check 2ndary BOV for leakage

Also look at .....

What is the load reading on monitor?

what is the O2 reading?

What is the Air flow reading?

What is the crank rpm on monitor?

[Guest boostin]

Dragging up an old thread, but any result with this??

[gtlegacy]

yea any results?

[sunnylong]

 crazymf said:

Well this has been a fun exercise to say the least

The problem we have is when you drive off from idle the primary turbo only boosts about 5psi, then when the secondary is supposed to kick in the boost drops to 0psi and thats it through the rest of the rev range.

Now i know everyone is thinking that i have a seized secondary turbo...We have done alot of diagnosing and part swapping with a known good vehicle.

Heres whats been done so far.

- Both turbos have been checked - Everythings fine there

- The ECU has been put into non boosting car from a boosting car - Didn't change a thing

- ECU from non boosting car put into boosting car - Boosting car still boosting

- Vacuum control box, same scenario as ECU - No change to either vehicle

- Exhaust shut off valve before secondary turbo removed and inspected - Perfect condition

- Cam timing checked - Perfect

- Airflow meter fitted from boosting car - No change

- Catalytic convertors checked - Not blocked

- Secondary intake shut off valve in intercooler checked - Working fine

- Vacuum hose configuration checked - All hoses go to where they should be

- Map sensor changed - No change

- BOV's checked - Perfect order

- Scanned for fault codes - No codes present, but when driving and watching what everything is doing on the select monitor, the knock retard is actually advancing the timing 9 degrees and the engine is pinking its nuts off

- Vacuum canister holds vacuum

Any help on this issue would be greatly appreciated. But we wont be giving up, a solution will be realised sooner or later, lol.

5 psi is basically the spring pressure on the wastegate. I have a EBC fitted on my car and if I turn off the BC I get 5 psi.

I'd check the solinoid and pressure differential sensor? If the pressure differential sensor incorrectly detects the pressure from the secondary turbo and thinks the pressure matches the primary turbo boost, it will open up the valve on the hose between the secondary turbo and the intercooler, thus all the pressure produced from Primary will leak from there....?

I'm just guessing....