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Old 12-22-2003, 08:52 PM   #1
Scooby Newbie
Member#: 51116
Join Date: Dec 2003
Location: WA
Default Strange BOV behaviors and strange noises from turbo

I have a GFB Stealth FX BOV adjusted to 100% atmospheric. It works fine in 1st and 2nd gear at all throttle positions and boost levels. In 3rd through 5th gears at higher boost levels, the BOV sounds as if it barely opens up when I let off the throttle. Sometimes it doesn't even make any venting sound at all. 50% of the time it would vent just fine at full boost. The other 50% of the time it would barely hear the BOV venting air and I would hear a weird sound coming from the turbo area, a very quick "pft...pft...pft...pft...pft", lasting 1 second at the most. It's very hard to hear that strange noise as it's very low and deep, however. I would only hear it when the windows are up and radio off. Sometimes the BOV would vent very quickly and then stops venting right away. I lift my foot very quickly to ensure a strong vacuum signal to the BOV, but it doesn't seem to help.

The BOV's spring is set at a rather loose setting. So loose that the BOV would leak out some air at idle. I've heard that setting the BOV spring too loose is better than too tight. Is this true?

What is going on? Am I just hearing wastegate noises or am I hearing pressure surge from not setting the BOV correctly?
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Old 01-09-2004, 04:38 AM   #2
Scooby Specialist
Member#: 45735
Join Date: Oct 2003
Location: ANYWHERE BUT Newport News
2002 Impreza WRX


It sounds like you've got a nasty case of compressor surge. I had the same thing on my HKS SSQV on 100% atmos.

Compressor Surge occurs when your BOV isn't venting enough air out of the IC system and the pressure left in the IC is slowing down your spinning turbine VERY quickly, making that "bark" sound you were talking about.

Technically, a loose spring would mean the BOV opens easily (like you said). I suspect a poor vacuum line connection, or a FUBAR BOV (like mine!) Try putting your stocker back on to check the Vacuum line, or try setting your BOV to another setting (recirc can help push the turbo to keep it from slowing down.)

BTW, you posted EXACTLY 19 years, 12 hours after I was born (12/22/84, 8:52 AM)
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Old 01-09-2004, 07:06 AM   #3
Scooby Specialist
Member#: 50287
Join Date: Dec 2003
Location: Franklin IN
02 WRX


i just like the fact of you posted about your b-day
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