correction- you cannot run the stock bypass open to atmosphere ... it does not fully stay closed while idling and will suck unfiltered air back into the intake manifold... this is bad...
the air getting sucked in under idle is not metered by the mass air meter and will cuase all kinds of headaches with the idle...
when hooked up to bypass, the bung where the bypass air goes is in the j pipe after the airflow meter... basically any air that gets back into the intake was already on that side of the meter so it dosent matter...
an aftermarket bov closes fully under idle vaccume... therefor does not draw air back into the intake or piping once the pressure has been released into the atmosphere...
think of it this way... when a bypass valve is working, it allows the charge in the pipe to basically make a big circle.. continuing to run through the turbo until the throttle is opened then it closes and all the air goes into the engine...
a BOV that dumps to atmosphere, just tosses that air.. instead of making the circle, and when the throttle is applied again, it requires the turbo to re-fill the system with air to create boost once again... this creates minor lag between shifts...the bigger the turbo the more noticeable the lag is, becuase other variables come into play... like how much exhaust pressure must be created to spin the turbo in the first place... AKA hotside size...
many people use bypass design to "anti-lag there cars with big turbos...
that being said a turbo as small as a vj-14 (stock capri turbo)refills the pipes rather quickly, and turbo lag is much less pronounced..
therefor ... get a BOV and dump to atmosphere...
let em know your comin... and if and when you ever decide to go with a bigger turbo you can worry about lag when the time comes....
