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By-pass Valve on Roots Supercharger #2656482 05/18/19 08:20 AM 05/18/19 08:20 AM
Joined: Jan 2003 Posts: 1,335 Oregon E earlymopar OP pro stock
earlymopar OP pro stock E Joined: Jan 2003 Posts: 1,335 Oregon	I'm interested in hearing from those of you who are running a by-pass valve (not the pop-off valve) on your roots style supercharger. I have an older model Magnuson I've adapted to my carbureted small block and am just to the point of final connections. I understand that a manifold vacuum signal is best but would like to hear (or see) how and where you tapped in to your manifold. - EM

Re: By-pass Valve on Roots Supercharger [Re: earlymopar] #2656487 05/18/19 08:41 AM 05/18/19 08:41 AM
Joined: Jan 2003 Posts: 8,027 Tulsa OK Bad340fish master
Bad340fish master Joined: Jan 2003 Posts: 8,027 Tulsa OK	I don't know that you can bypass a blower in a carb'd application. That bypassed air will have fuel in it. 68 Barracuda Formula S 340

Re: By-pass Valve on Roots Supercharger [Re: Bad340fish] #2656609 05/18/19 03:52 PM 05/18/19 03:52 PM
Joined: Feb 2007 Posts: 2,578 sweden 1 1Fast340 master
1Fast340 master 1 Joined: Feb 2007 Posts: 2,578 sweden	There are valves that recirculates air from under the supercharger back up to under the carb on twinscrew superchargers to prevent them from destroying themselfs on the street and those work fine in carbed applications,i guess the same concept could be used on a rootsstyle.

Re: By-pass Valve on Roots Supercharger [Re: 1Fast340] #2656709 05/18/19 10:33 PM 05/18/19 10:33 PM
Joined: Dec 2007 Posts: 12,587 Great Neck,LI,new york hemi-itis I Live Here
hemi-itis I Live Here Joined: Dec 2007 Posts: 12,587 Great Neck,LI,new york	Why would they come apart??Built with good parts see at high as 7k rpm and the boost spike at the shift. HEMI-ITIS has no cure. My condition is fully BLOWN!!

Re: By-pass Valve on Roots Supercharger [Re: earlymopar] #2656758 05/19/19 08:24 AM 05/19/19 08:24 AM
Joined: Jan 2003 Posts: 1,335 Oregon E earlymopar OP pro stock
earlymopar OP pro stock E Joined: Jan 2003 Posts: 1,335 Oregon	For those of you not familiar, "the best kept secret in forced induction is the little known bypass valve that allows the supercharger to be extremely efficient in terms of economy and parasitic power loss. The bypass is operated by a vacuum actuator control unit that is normally closed. When vacuum is high (idle-cruising) the actuator opens the bypass valve, equalizing the vacuum pressure throughout the system. When boost is required (accelerating) the vacuum is decreased and the bypass valve instantly closes, causing pressure to increase into the cylinders. This vacuum condition virtually eliminates the normal parasitic power loss of a forced induction system." I solved the issue that caused me to post this thread. I'm simply using the vacuum port in the manifold that was provided for power brakes. BTW, attached is the same Magnuson I have, shown here on a Chevy.... Thanks, - EM Last edited by earlymopar; 05/19/19 08:25 AM.

Re: By-pass Valve on Roots Supercharger [Re: earlymopar] #2656828 05/19/19 11:11 AM 05/19/19 11:11 AM
Joined: Jan 2003 Posts: 14,498 So. Burlington, Vt. F fast68plymouth I Live Here
fast68plymouth I Live Here F Joined: Jan 2003 Posts: 14,498 So. Burlington, Vt.	Apparently it works.......but my thoughts were that it would be a tuning nightmare for part throttle operation since your recirculating air that already has fuel in it. With MPFI, the fuel is introduced into the system after any recirculating of inlet air has been done. 68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads

Re: By-pass Valve on Roots Supercharger [Re: fast68plymouth] #2656853 05/19/19 12:40 PM 05/19/19 12:40 PM
Joined: Dec 2007 Posts: 12,587 Great Neck,LI,new york hemi-itis I Live Here
hemi-itis I Live Here Joined: Dec 2007 Posts: 12,587 Great Neck,LI,new york	If this vacume switch is suck a wonderful item,why have they not been utilized in larger superchargers?? HEMI-ITIS has no cure. My condition is fully BLOWN!!

Re: By-pass Valve on Roots Supercharger [Re: hemi-itis] #2657141 05/20/19 08:53 AM 05/20/19 08:53 AM
Joined: Jan 2003 Posts: 1,335 Oregon E earlymopar OP pro stock
earlymopar OP pro stock E Joined: Jan 2003 Posts: 1,335 Oregon	They are in some cases..... - EM

Re: By-pass Valve on Roots Supercharger [Re: hemi-itis] #2657164 05/20/19 09:57 AM 05/20/19 09:57 AM
Joined: May 2004 Posts: 12,388 Taxes & Virus's R-US, NY Dragula I Live Here
Dragula I Live Here Joined: May 2004 Posts: 12,388 Taxes & Virus's R-US, NY	They are used on larger ones, if its a Whipple.... '70 Cuda,...605 EFI Hemi Street Car (6.20 best pass, 1.33 60ft) https://www.youtube.com/watch?v=WYw6RA-k5Bk (6.25 at 108.75mph from inside car) https://www.youtube.com/watch?v=3zQEb9uxFng (6.25 at 108mph from outside car) https://www.youtube.com/watch?v=JCvfzsC4NgM (9.9) '66 Barracuda AWB Stretched nose Blown 440 Car in build stage '71 Duster Drag Car 400 Low Deck 512 best 6.002 at 115.44mph https://www.youtube.com/watch?v=Znuo3jMUXTk

Re: By-pass Valve on Roots Supercharger [Re: Dragula] #2657213 05/20/19 12:33 PM 05/20/19 12:33 PM
Joined: Jan 2003 Posts: 1,335 Oregon E earlymopar OP pro stock
earlymopar OP pro stock E Joined: Jan 2003 Posts: 1,335 Oregon	Yep. I've seen them on Roots, Whipple & Centrifugal with both carburetion and injection. That's a great picture. Thank you. - EM

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