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Old 12-31-2012, 03:47 AM   #1
jonney_boy
Scooby Specialist
 
Member#: 28747
Join Date: Nov 2002
Chapter/Region: VIC
Vehicle:
06 WRX

Default '06 wrx overboosting.

I have a '06 wrx, 100,000km, cobb stage 1 tune (91 Octane CA map), 5 speed.

STI axle back, snorkel removed, everything else (intake/exhaust) is stock.


Anyhow, Ever since new (even before the Cobb) the car has always boosted a couple psi past target and dropped right back down to target in about a 1/2 second (if you mash it). After the stage one tune, the same would happen, but the scale just moved up a couple pounds (as per the tune). I was still borderline within the tolerances of the tune.

Anyhow, A year ago, I had 4 people and luggage in the car, hit a hill in 5'th with some cold weather and when I rolled on the gas I threw a Overboost code. The computer reset itself, asked around and people said "once" in a while is ok. Seeing it's once in 5 years.. and it's not happened again (it's been a year already) I assumed all is well.

Anyhow, today, rolling onto the gas again in 3rd (about 2500 - 2600 rpm when I started giving it gas) I saw the boost guage shoot up in the corner of my eye. I didn't get a good look but i'm thinking 18psi and climbing fast. I let of the gas right away, down shifted and didn't have any other problems. No CEL/codes, car runs fine. I did notice that at partial throttle and at low rpms (2500'ish) the car did seem to want to over boost. I didn't want to push my luck and just drove around this condition. I didn't seem to have problem with higher (3200-3500rpm) WOT pulls.


I guess my question is...... what could have caused the "sudden" urge for the car to over boost. Is it a huge concern? or was it just a fluke? Is there some maintenance item that I might have overlooked that might cause this?

One thing to note. I did put in a tank of 92 chevron from Seattle today. The car usually only sees 94 chevron locally.

TIA
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Old 12-31-2012, 01:26 PM   #2
brett192
Scooby Specialist
 
Member#: 274252
Join Date: Feb 2011
Chapter/Region: W. Canada
Location: Vancouver Island, BC
Vehicle:
2002 WRX Sedan PSM
Stage 2 w/ 6 speed

Default

I'm quite sure that I have read on here about the 2.5L WRXs overboosting since they use the same turbo (and wastegate) as the 2.0, but the larger motor obviously expells more exhaust volume, so the small wastegate can't keep up. Installing an external wastegate or having your turbo ported and polished supposedly remedies this problem. This doesn't apply to my 2.0L, so I didn't pay much attention. I'm sure the experts will chime in shortly. Good luck
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Old 01-02-2013, 12:26 AM   #3
jonney_boy
Scooby Specialist
 
Member#: 28747
Join Date: Nov 2002
Chapter/Region: VIC
Vehicle:
06 WRX

Default

Yes I have read about that too, but to my understand that only happens under WOT and at 4000-5000 rpm.

From what I read, the car will hit target and then slowly creep up past target as the wategate get's overwhelmed. My case is the opposite, I get a "spike" of overboost before it quickly drops down to target.
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Old 01-02-2013, 01:11 PM   #4
minifreak
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Member#: 116914
Join Date: Jun 2006
Chapter/Region: VIC
Location: Beautiful British Columbia
Vehicle:
2006 WRX Wagon
Obsidian Black

Default

Boost spike and boost creep are some what different. It is true that the 2.5L are more prone to boost creep due to the tiny little TD04.

Boost spike usually means the ECU isn't able to control the instantaneous boost change. You can play around with either the Turbo Dynamic table or one of the wastegate tables that sets the amount of wastegate componsation based on target boost.

With your car running stock turbo back it would be less likely for it to experience turbo creep.
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