What is the difference between a BOV and bypass? How do they work, are they necessary?
A BOV is a Blow off Valve. These horn shaped device is mounted along the intercooler piping somewhere between the turbo and the throttle body. It will open up once the throttle blade is closed in order to bleed off all the air in the system between the turbo and the throttle blade. The blown off air is simply blown into the atmosphere. A bypass valve looks very similar to a BOV and many BOV’s can function as a bypass valve. The difference being is the air that is blown off from the bypass valve is recirculated via a hose back into the air intake system somewhere between the MAF and the turbo. A bypass valve and not a BOV is necessary on draw through MAF cars, otherwise you would be blowing off metered air. A Draw through MAF is where the mass airflow meter is mounted in front of the turbo. There is no definitive answer if a BOV or bypass is necessary. However many people agree that utilizing a BOV or bypass can extend turbo life and increase spool time between shifts.
