Any Ideas about Boost Spiking?

[MintLord]

Hi all,

 

Thought I'd just get some ideas thrown at me to diagnose what my issue is. I seem to get some spiking with boost on the primary turbo, and low boost on the secondary. Primary Turbo will spike to 17PSI quickly, and then will settle back down to 13 very quickly after hitting the 17PSI number.

 

The second turbo seems to sit at 13PSI constant, no higher or lower. Definitely is more power on the second turbo, but 13 seems low from what I'm reading.

 

I'm definitely not ruling out bad Boost gauge, but I don't think that's the issue here. I've got the boost gauge plumbed into line 11, just out from the BBOD.

 

Any Ideas? Obviously most likely Vacuum tube issues - I had a leak from my BOV, after installing an aftermarket BOV, and adding some gasket maker to the BOV, it's been much more consistent. So potentially more boost leaks elsewhere?

 

All testing I do of boost pressure is around 90-100km, and usually third gear pulls for the second turbo.

[Setnev]

Check the vacuum lines on your wastegate. If the line becomes disconnected or has a leak, boost will climb dangerously fast and will not dump exhaust pressure causing an over boost condition. That buys a one way ticket to grenading the motor.

[MintLord]

Check the vacuum lines on your wastegate. If the line becomes disconnected or has a leak, boost will climb dangerously fast and will not dump exhaust pressure causing an over boost condition. That buys a one way ticket to grenading the motor.

 

Awesome! That was exactly it, thanks - Dodgy vacuum line off the primary turbo wastegate!

 

Any input on the boost numbers I'm getting? I feel like they're a bit low

[Setnev]

That's great news! Glad to have fixed that issue.

 

On the boost numbers, see if you have any boost leaks by spraying soapy water on your intake tubes. Rev the engine in park/neutral to a few thousand RPM to build a couple pounds of boost and see if you catch any air bubbles forming.

 

Don't forget to have a look at the y-pipe on the back of the intercooler. Those like to leak quite frequently.

 

If you have no leaks, you could be facing a bad boost control solenoid. On the twin-turbo models, it's supposed to regulate the boost pressure between the primary and secondary turbo. There are three modes: fully open (no boost), fully closed (full boost), and pulse (regulated boost). When there is a fault and the BCS cannot properly modulate the pressure, the ECU goes into a "protect mode" that relieves the boost pressure to prevent overboost and damage to the engine. My thoughts are that if the BCS is bad, the ECU is going into "protect mode", opening the wastegate, and dumping boost. From my limited research, when both turbos come online, you should yield about 13-16 psi (1 - 1.25 bars).

 

I found an interesting article regarding the EJ208 and it's unique tuning over on UKLegacy

 

http://www.uklegacy.com/forums/index.php/topic/7815-how-to-increase-primary-boost-i-have-the-answer/

 

I wish I could be of more help to you, but we don't have the Twin-Turbo Legacy's here in the states yet, but when they become legal, you can bet I'll be first in line to get one. Only 3.25 more years to go.

[MintLord]

Awesome - I appreciate your help.

 

Looks like my Car is working as intended based on that thread. I'm interested in looking at that mod - I've done the line 10 mod but looks like it's different from the standard line 10 mod.

 

Edit: I've done that line 10 mod! I don't get quite the same results as the guy in that thread, but I get around 14PSI peak with that mod, which I'm okay with over stock.