# The dumb thing is that an atmospheric BOV looses power on the WRX (more)

Posted by Matt (02 WRX / 96ZJ) on September 16, 2004 at 10:31:47: In Reply to: Why one of nearly every WRX owners first "performance" modifications a loud ass BOV? :mad: posted by Maximamike on September 16, 2004 at 08:37:24: The WRX comes stock with a recirculation valve which vents any pressure in the intake after the turbo back into the intake before the turbo when the throttle plate is suddenly closed. This prevents a reverse surge through the compressor. The ECU expects this recycled air to be present, and tunes the a/f ratio accordingly. If you install a BOV that vents to the atmosphere the you get the nifty PSSSSSHHH sound, the air is not recycled back into the intake, the a/f ratio is really rich, and the car looses power. Plus, the stock recirc valve can hold pressure to support upwards of 300hp, so there is really no point changing it out. - Matt pimpin the mid 13s with stock recirc valve and muffler Replys:

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: : The WRX comes stock with a recirculation valve which vents any pressure in the intake after the turbo back into the intake before the turbo when the throttle plate is suddenly closed. This prevents a reverse surge through the compressor. The ECU expects this recycled air to be present, and tunes the a/f ratio accordingly. : If you install a BOV that vents to the atmosphere the you get the nifty PSSSSSHHH sound, the air is not recycled back into the intake, the a/f ratio is really rich, and the car looses power. : Plus, the stock recirc valve can hold pressure to support upwards of 300hp, so there is really no point changing it out. : - Matt : pimpin the mid 13s with stock recirc valve and muffler