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Supercharger blow-off or bypass valve?


BulletMagnet

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It's a topic my brother and his friends on the Celica forums have been discussing at great length, but I wanted to pick the brains of all the S/C owners on here.

 

th_d2e37804.jpg

 

Now look at the vid and tell me whether the BOV should be open while on idle and only close when engine needs the charge.

To me it makes sense, since the S/C setup has no waste gate and thus any unneeded "boost" should be expelled to the atmosphere.

My bro is running a Rotrex and a Tial BOV with a 3psi supercharger spring in it. Previously, the guy that fitted the whole S/C setup had a 13psi turbo spring in it that caused "fluttering" on idle, which we believe to be to be excess "boost" going back to the charger, which is bad.

 

Please give me your insights, thank you

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Can't quite make out what is happening in the video...but your right in what your saying.

 

The Bypass valve in a supercharger system should be open any time that the charge air isn't required ie when idling, cruising, any time your not accelerating really. As you said, if it remains closed when off the throttle, then the excess air that the engine can't physically ingest is forced back through the charger and out the air filter which causes the fluttering sound due to the charger trying to stall.

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Indeed Sam, that's what I think too. The surge back shouldn't happen in the first place as it could damage the charger, even if it's in the long run. And considering that the Rotrex is sold as a sealed unit, it's even more important to avoid any surge back.

One of the authorised sellers for Rotrex, TTS, said that once the sealed unit is damaged or opened, they get scrapped and replaced.

 

FYI, the BOV in above vid is open during idle and when the engine revs, it starts to close and is fully shut on wide open throttle.

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