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Old 09-13-2019, 11:51 PM   #1
Nick07sti
Scooby Newbie
 
Member#: 385386
Join Date: Mar 2014
Chapter/Region: South East
Vehicle:
2007 STi
WRB

Default Cobb Stage 2 07 Sti not reaching target boost (datalog)

07 sti with 40k original miles. Invidia catted DP and full exhaust. Stock intake on 93 oct. Running Cobb stage 2 93 oct. The first log is normal waste gate and the second high waste gate. I pressurized and tested the system for a boost leak and found nothing. I am not sure why I can't hit the 19.5 psi target. The HWG map just barely touches 18 psi but my DAM dropped and I had a light knock. Any ideas what my problem is and how to reach target?

Normal WG:
https://drive.google.com/file/d/1OsL...ew?usp=sharing

High WG:
https://drive.google.com/file/d/1KvG...ew?usp=sharing
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Old 09-14-2019, 06:26 AM   #2
Blktrax
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Member#: 220971
Join Date: Aug 2009
Chapter/Region: South East
Location: West, NC
Vehicle:
2002 WRX 224K Mi.

Default

Donít get hung up on not exactly hitting boost targets.

Looking at the HWG log, youíre at 91% injector duty cycle. Youíre basically out of injector at this point anyway without looking at AFR #ís

Things to consider,

1, Ambient temp and elevation. Have a profound effect on overall boost and correction. Higher intake temps=more potential for knock. Also these off the shelf tunes have to operate from sealevel atmosphere to the highest one can drive over mountains. Barometric adjustment/compensation is key to not being towed home.

2. Age of hardware 12yr old wastegate spring/diaphragm and boost controller.
Over 5800 RPM the wastegate starts to ramp up again as boost under targets over 2psi error, likely the exhaust flow is just starting to force the wastegate or recirc (blow off, under boost) valve open. Doing the old tricks of tightening the wastegate arm if yours has it can work to some degree. However if improperly or over tightened can lead to boost oscillation.

Main thing is youíre not overboosting and itís not constantly correcting. Giving that surging feeling when accelerating.

Just run the HWG map and occasionally watch for knock and enjoy it. Otherwise youíre looking at dropping some bills on more fuel system and a ProTune.

Last edited by Blktrax; 09-14-2019 at 06:43 AM.
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Old 09-14-2019, 11:17 AM   #3
Nick07sti
Scooby Newbie
 
Member#: 385386
Join Date: Mar 2014
Chapter/Region: South East
Vehicle:
2007 STi
WRB

Default

Quote:
Originally Posted by Blktrax View Post
Donít get hung up on not exactly hitting boost targets.



Looking at the HWG log, youíre at 91% injector duty cycle. Youíre basically out of injector at this point anyway without looking at AFR #ís



Things to consider,



1, Ambient temp and elevation. Have a profound effect on overall boost and correction. Higher intake temps=more potential for knock. Also these off the shelf tunes have to operate from sealevel atmosphere to the highest one can drive over mountains. Barometric adjustment/compensation is key to not being towed home.



2. Age of hardware 12yr old wastegate spring/diaphragm and boost controller.

Over 5800 RPM the wastegate starts to ramp up again as boost under targets over 2psi error, likely the exhaust flow is just starting to force the wastegate or recirc (blow off, under boost) valve open. Doing the old tricks of tightening the wastegate arm if yours has it can work to some degree. However if improperly or over tightened can lead to boost oscillation.



Main thing is youíre not overboosting and itís not constantly correcting. Giving that surging feeling when accelerating.



Just run the HWG map and occasionally watch for knock and enjoy it. Otherwise youíre looking at dropping some bills on more fuel system and a ProTune.


Thank you Blktrax. I am in Florida and the temp was 85 degrees out. I also took my silencer off of the stock intake. Could this be an issue? Also, I have not heard of tightening the Wastegate arm. Is there any info on how to do this?
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Old 09-14-2019, 01:28 PM   #4
Blktrax
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Member#: 220971
Join Date: Aug 2009
Chapter/Region: South East
Location: West, NC
Vehicle:
2002 WRX 224K Mi.

Default

Quote:
Originally Posted by Nick07sti View Post
Thank you Blktrax. I am in Florida and the temp was 85 degrees out. I also took my silencer off of the stock intake. Could this be an issue? Also, I have not heard of tightening the Wastegate arm. Is there any info on how to do this?
The silencer wouldnít have an effect, and not all turbos had the ability to adjust the arm. I would suggest you seek a tuner or someone who has done it before, due to the potential to break the wastegate arm or overboost and damage the engine.
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