GoFast Bits first pioneered the Hybrid system in 1998, which was the first valve available on the market to use both an atmosphere-venting trumpet and a plumb back outlet – their competitors are only just starting to follow suit.  Here’s the technical information on what makes this Hybrid system a world’s first.

First, a little background on what really happens when you lift off the throttle after hard acceleration.  There is an initial pressure spike that begins as a result of the throttle closing, the air backs up against the throttle plate and a high-pressure wave is formed.  It is important for the valve to open quickly to vent this high pressure wave and prevent it from passing back through the compressor (if the wave does pass through the compressor it causes a fluttering noise, commonly referred to as compressor surge).

However, once the pressure spike is evacuated the turbo will continue to “freewheel” and pump large volumes of air out the valve.  In a car with an airflow meter, it is this volume of air passing through the meter that can sometimes cause backfiring, since the ECU will still be delivering fuel for the escaping air (a bypass valve simply re-circulates the air back to the inlet side of the turbo).

The Hybrid system addresses these issues by not only using two outlets, but also by positioning them to open sequentially.  The return outlet is positioned at the very bottom of the valve so that it will cent with the slightest movement of the piston, while the trumpet is 4mm higher so that it opens after the return.  When the valve vents, the travel of the piston is affected by a number of things, which will in turn affect how much air is distributed to each port.

During light throttle lift-offs when cruising, the piston will only lift about 4 – 6 mm, so the majority of the air is re-circulated and it will not make much noise.  When lifting off after hard acceleration, the piston will open up fully to vent the pressure spike as rapidly as possible, and as the piston begins to close it forces more air into the return outlet.  This helps to prevent backfiring and ECT fault codes by re-circulating more of the air during the “turbo freewheeling” period.