Blow Off Valve on a SC S-R??

Speed Freek said:

I was making the point that his truck doesnt need one it uses a bypass valve to control boost levels and act as a wastegate sort of speak. No need for a BOV on the Tacoma screw type S/C.

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If the definition of a BOV is to bleed off boost after meeting a predetermined PSI, the bypass valve never functions as a BOV. The boost of the TRD supercharger is a function of speed and pumping efficiency. The bypass requires vacuum to actuate and none is available during boost; therefore the bypass cannot operate as a BOV.

On the other hand, I have actually installed an electrically switched vacuum valve in-line with my bypass so I can lock-out boost at all RPM ranges. When I engage my cruise control switch it feeds a relay that locks the bypass open (high vacuum state) and breaks the signal to my TRD 7th injector.

Kind of like a Jekyl and Hyde switch.

This prevents the dying cat sound when you want to drive up a mountain at a leisurely pace. Also seems to add about 1.5 MPG, although I am not sure how much is simply due to eliminating the temptation of getting deeper into the throttle and feeling the boost of the supercharger.

Speed Freek said:

Good way to force that SC to boost, great trick. Might as well make boost, its already spinning for gods sake!!

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No, just the opposite, I am killing boost when I really don't want it. The whining gets tiresome when all you want to do is ease up the road at light throttle. Sounds great when at full throttle and you want quick acceleration but sometimes I like to be able to drive without the noise of the SC every time I slightly tip-in the throttle. Wrong time for me to relate my setup, obviously brought confusion to the thread.

Speed Freek said:

Is you post above more meant for a Wastegate than a BOV?

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I thought a wastegate allowed exhaust gas to bypass the turbine to keep a turbo from over spooling (exhaust side). Conversely, I though the BOV was used to release pressure in the intake when the throttle body is closed on a turbo system. (Intake side)

I interpreted the OP's question about a BOV to relate to a desire to limit the boost of the supercharger. My point is there are no provisions to do so and that the bypass valve you offered up cannot function in that capacity. The bypass valve is simply an on/off switch that functions only if it has high manifold vacuum present.