Supercharge and blow off valve
Registered User
Joined: Aug 2005
Posts: 4,585
Likes: 2
From: Anaheim Hills, CA
Originally Posted by vick781
all i have to say is "shibby!"
Originally Posted by Badmonkey
The superchargers come with a "bypass" valve. The valve is designed to open up while under vacuum. This sends the compressed air back through the intake. You can vent this to the atmosphere but the sound is not like that of a turbo. The release is long and constant. I recently installed a TurboXS BOV on my car and had it vented to the atmosphere, it was very loud. The sound was like a huge blow dryer at idle, since it was dumping all of the air out. While under boost, the valve would close and quiet down. When you let off the throttle it gave off a long whoosh and then it stayed at the normal loudness at idle. It sounded very crappy, to say the least. So, I routed the discharge to the intake and the sound is now gone, for the most part. I do get a little more boost with the BOV compared to the cheap bypass valve. I was hitting 10.5 psi before, now I see 11.0 psi.
Hope that helps...
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Joined: Dec 2003
Posts: 664
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From: England
Originally Posted by z350boy
A supercharged engine would not use a blow-off valve. With Supercharging the "blower" works off the engines crankshaft; the engines RPM drives the unit. Turbochargers work off the engines exhaust flow which is used to power the turbos. The blow-off valve is needed for a turbocharger because it helps to regulate the amount of pressure being sent to the unit. 
It's not a good race unless they can see your tailights!!
It's not a good race unless they can see your tailights!!
No, your confusing yourself with a wastegate. A BOV serves exactly the same purpose on a supercharged car as a turbo car, to release pressure that is trapped between the discharge of the compressor and the throttle plate when it shuts (gear change, etc). The release of this pressure prevents the turbine stalling, and protects the compressor from potential damage that can occur because of this backflow, through the compressor.
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Joined: Apr 2005
Posts: 58
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From: Ann Arbor, MI
Originally Posted by baptist
No, your confusing yourself with a wastegate. A BOV serves exactly the same purpose on a supercharged car as a turbo car, to release pressure that is trapped between the discharge of the compressor and the throttle plate when it shuts (gear change, etc). The release of this pressure prevents the turbine stalling, and protects the compressor from potential damage that can occur because of this backflow, through the compressor.
Originally Posted by neffster
My guess is that you have an automatic. Auto's don't let off of boost when they shift gears so you don't have the turbo BOV sound when you let off of the gas and shift. The "bypass" valve on the Vortech, with a 6MT sounds pretty similar to a turbo BOV.
Hope that helps...
Hope that helps...
Originally Posted by Badmonkey
I have a manual and know how my system works. The BOV does work while shifting, but it is a longer sound than a turbo, due to the characteristics of the supercharger, which is always spinning. When the car is at idle the sound from the air blowing through the BOV is VERY loud. While driving and not boosting, the sound is VERY loud. While driving and boosting, it gets quiet until the shift, yes you do hear a whoosh, but is is a lot longer in duration than a turbo. I enjoy a BOV sound, too, but the sound while there is still vacuum, is terrible.
Originally Posted by Badmonkey
I have a manual and know how my system works. The BOV does work while shifting, but it is a longer sound than a turbo, due to the characteristics of the supercharger, which is always spinning. When the car is at idle the sound from the air blowing through the BOV is VERY loud. While driving and not boosting, the sound is VERY loud. While driving and boosting, it gets quiet until the shift, yes you do hear a whoosh, but is is a lot longer in duration than a turbo. I enjoy a BOV sound, too, but the sound while there is still vacuum, is terrible.
You might need to rotate the BOV 180 degrees to get the filter to fit.
Originally Posted by Badmonkey
I have a manual and know how my system works. The BOV does work while shifting, but it is a longer sound than a turbo, due to the characteristics of the supercharger, which is always spinning. When the car is at idle the sound from the air blowing through the BOV is VERY loud. While driving and not boosting, the sound is VERY loud. While driving and boosting, it gets quiet until the shift, yes you do hear a whoosh, but is is a lot longer in duration than a turbo. I enjoy a BOV sound, too, but the sound while there is still vacuum, is terrible.
Big difference. I can now hear the engine and exhaust while cruising with the windows down and the high pitched whistle is now very muffled. Makes for a much nicer experience and even gives the illusion that the car is faster. Maybe the slight restriction from the filter lets the vacuum reverse faster and move into boost a little quicker.
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