Supercharger by-pass valve

[Blown3000]

I'm thinking about installing a by-pass valve on my Maguson supercharger, is it worth the time and money? Also any negative or positive effects on the system in general?

[IPD]

why? so that you can "stay out of boost? i'm not sure i understand the point.

[Prizefighter]

why? so that you can "stay out of boost? i'm not sure i understand the point.

The by-pass valve works similar to a BOV on a supercharged application, with one difference: instead of venting the air to atmosphere it takes the boost pressure and by-passes it into the intake. A recirculated BOV works in the same way

[IPD]

The by-pass valve works similar to a BOV on a supercharged application, with one difference: instead of venting the air to atmosphere it takes the boost pressure and by-passes it into the intake. A recirculated BOV works in the same way

ok, but why? is your supercharged system capable of generating that kind of power to justify it? i just have a hard time envisioning where this is of significant benefit to SC owners (on the 3/s) where virtually every SC application i've ever seen is tuned for < 10lbs of boost. usually less than 8. i'm having a hard time picturing how throttle-lift will damage a supercharger in the same manner it will a turbocharger.

[ibsorgn]

A supercharger bypass valve (SBV) is not the same as a blow off value (BOV). A BOV is used to prevent compressor surge, an event that happens when lifting off the throttle of an unvented, turbocharged engine. Without a BOV, high pressure air, trapped in the intake system, would cause a pressure wave that would be forced back into the compressor which can rapidly slow the turbine or even stall it.

A SBV is a vacuum operated device installed between the throttle body and supercharger. When high vacuum is present opens, equalizing the vacuum pressure through out the intake system which virtually eliminates all the parasitic loss that the SC has on the engine. When you depress the accelerator, vacuum falls and the SBV instantly closes allowing boost to build. Magnuson claims that their MP90 uses less than 1/3 hp when crusing a 60mph.

In other words its for fuel economy - by preventing boost from building under lite loads.

I installed my SBV about a year ago and realized about a 2mpg increase in fuel economy. I purchased my SBV from Magnuson, I think I spent about $60 however ever due to hood clearance problems I mounted mine on the bottom side of the SC which was a challenge in itself.

Hope this answers your questions.

[stealthee]

I know the Grand Prix's come from the factory with a bypass valve. I, however, do not believe it is located between the TB and the SC. The TB is mounted directly to the SC in that application.

[IPD]

A supercharger bypass valve (SBV) is not the same as a blow off value (BOV). A BOV is used to prevent compressor surge, an event that happens when lifting off the throttle of an unvented, turbocharged engine. Without a BOV, high pressure air, trapped in the intake system, would cause a pressure wave that would be forced back into the compressor which can rapidly slow the turbine or even stall it.

A SBV is a vacuum operated device installed between the throttle body and supercharger. When high vacuum is present opens, equalizing the vacuum pressure through out the intake system which virtually eliminates all the parasitic loss that the SC has on the engine. When you depress the accelerator, vacuum falls and the SBV instantly closes allowing boost to build. Magnuson claims that their MP90 uses less than 1/3 hp when crusing a 60mph.

In other words its for fuel economy - by preventing boost from building under lite loads.

I installed my SBV about a year ago and realized about a 2mpg increase in fuel economy. I purchased my SBV from Magnuson, I think I spent about $60 however ever due to hood clearance problems I mounted mine on the bottom side of the SC which was a challenge in itself.

Hope this answers your questions.

that makes sense to me.

[Prizefighter]

A supercharger bypass valve (SBV) is not the same as a blow off value (BOV). A BOV is used to prevent compressor surge, an event that happens when lifting off the throttle of an unvented, turbocharged engine. Without a BOV, high pressure air, trapped in the intake system, would cause a pressure wave that would be forced back into the compressor which can rapidly slow the turbine or even stall it.

A SBV is a vacuum operated device installed between the throttle body and supercharger. When high vacuum is present opens, equalizing the vacuum pressure through out the intake system which virtually eliminates all the parasitic loss that the SC has on the engine. When you depress the accelerator, vacuum falls and the SBV instantly closes allowing boost to build. Magnuson claims that their MP90 uses less than 1/3 hp when crusing a 60mph.

In other words its for fuel economy - by preventing boost from building under lite loads.

I installed my SBV about a year ago and realized about a 2mpg increase in fuel economy. I purchased my SBV from Magnuson, I think I spent about $60 however ever due to hood clearance problems I mounted mine on the bottom side of the SC which was a challenge in itself.

Hope this answers your questions.

Maybe on the 3/S application the SBV is used differently. I had a mustang with a vortech S/C that used the SBV to prevent compressor surge, and I ran just about 9lbs of boost. Maybe the application between centri blowers and the roots type is the main difference.

[anyonebutme]

Maybe the application between centri blowers and the roots type is the main difference.

yes..

[Blown3000]

In other words its for fuel economy - by preventing boost from building under lite loads.

I installed my SBV about a year ago and realized about a 2mpg increase in fuel economy. I purchased my SBV from Magnuson, I think I spent about $60 however ever due to hood clearance problems I mounted mine on the bottom side of the SC which was a challenge in itself.

Hope this answers your questions.

Are you satisfied with the way the SBV works? Any effect on performance? Could you be more specific about your comment "mounted mine on the bottom side of the SC which was a challenge in itself."
Many thanks

[Blown3000]

In other words its for fuel economy - by preventing boost from building under lite loads.

I installed my SBV about a year ago and realized about a 2mpg increase in fuel economy. I purchased my SBV from Magnuson, I think I spent about $60 however ever due to hood clearance problems I mounted mine on the bottom side of the SC which was a challenge in itself.

Hope this answers your questions.

Are you satisfied with the way the SBV works? Any effect on performance? Could you be more specific about your comment "mounted mine on the bottom side of the SC which was a challenge in itself."
Many thanks

[ibsorgn]

Are you satisfied with the way the SBV works? Any effect on performance? Could you be more specific about your comment "mounted mine on the bottom side of the SC which was a challenge in itself."
Many thanks

Yes I'm satisfied however I was surprised that the fuel mileage increased that much. Because it did, it goes to show that the SC does put a load on the motor maybe similar, in my case to running the AC. If I'm not mistaken Mr. Knight told me, that at 8 pounds of boost, would figure a load around 14hp. Effect on performance, I don't see anything different. Power comes on like normal. I'm running a 4th gen Magnuson MP90 which sets at the 3 o'clock position. My system is Knight's 12 gen which positions the SC more along the centerline of the hood. I believe that was done to provide more hood scoop options unlike the earlier versions which were offset to the driver's side. Because of the SC positioning, the SBV falls right under the back edge of the rear valve cover which leaves very little clearance for the actuator arm to swing freely. I was able to create enough clearance by grinding on the valve cover and reducing the length of the SBV butterfly shaft. This all could have been avoided had I, either provided a higher hood scoop and mounting the SBV on the top side (left side), or adding a spacer on the lower intake manifold which would raise the SC and provide more clearance. A good choice would be a non metallic spacer (3/8") which would also reduce heat transfer.