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Message: <blockquote data-quote="kb1982" data-source="post: 1228724" data-attributes="member: 18723"><p>Most kits come with a bpv now days. Some of the old kits that made 5 pounds used to not come with them. Superchargers are spinning constantly, even at idle producing more airflow than what the engine needs. Thats why some supercharger engines surged really bad, they didnt have a bpv to vent the unneeded airflow. The bpv is referenced with a vacuum line, so when the engine is under light load or idling and the vacuum is high, it holds the bpv open and allows it to bleed off the pressure. When you mash the gas, engine looses vacuum signal and the bpv closes, reroutes the air through the intake and the boost builds. The bpv also lets the air divert when the drivers lets off the throttle, thus closing the throttle blades. If this uneeded air rushed into the closed throttle blade, it would be reverted into the intake plumbing, then the compressor housing possibly damaging the supercharger. As for the running rich with a bov, either a chip and a tune is needed to correct fueling issues along with larger injectors, or as in most kits, it comes with a fuel management unit. The fuel management unit (FMU), is also vacuum/boost referenced just like the bpv. When the fmu loses vacuum, it ramps up fuel pressure at a predetermined rate to prepare for the oncoming rush of more air.</p></blockquote><p></p>