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I have a '92 Mustang with a Paxton SN89 on it. I installed it this past summer and about a month later my rings were shot and I am getting blow-by. My question is has anyone installed a bypass valve on a SN series so that the boost is not forced in when you let off the gas? If so what kind and where did you mount it. Pics would be helpful. I have a new motor for the car, but I don't want it to do the same thing the old motor did. BTW I have the plastic discharge tube.
Thanks,
Ryan
your cylinder rings are shot??? that wasn't caused by not having a bypass valve.
how much boost are you seeing?
Quote:
Originally Posted by ray95
I am not sure on how much I am actually seeing. I have a 4" pulley on the unit and I was told around 8-10 psi. The reason I am asking about the bypass valve is because I just don't want something like not having that mess my new motor up. The tune was bad on my current motor which is why it's rings washed out. The fuel pressure was too high and the FMU I had was calibrated for 19lb injectors and I have 24lb injectors.
Well a bypass isn't gonna effect your rings. But if you don't have one it is very hard on the bearings and the impeller.
you wont have to worry about the motor messing up. not having the bypass with a high boost application will mess up the blower. when you let off the gas, the throttle plate is closed so the only other place the forced air has to go is back into the supercharger and that's not good for the blower. a bypass gives the air someplace to go instead of rushing back into the blower. the air goes through the bypass and into your inlet tube for the blower and gets recycled.
you should be fine installing your new motor. just get it tuned and get a bypass installed to save your motor.
I dont think you are seeing 8-10# of boost from a 4inch pulley thats stock! The unit is prob 5-6#s stock. They say that anything over 7#s should have a bypass valve But you should throw one on there just to be safe
No, 4.5" is stock. I had that on there first and I noticed a pretty good difference with the 4" pulley.Quote:
Originally Posted by Crazyhorse88
you can pick up one of the various bosch bypasses, part #'s ending in 110 or 108 woulld work for your application. The 108 can be had a bit cheaper. From there, you'll need either some 3/4" or 1" heater type hose, a couple bungs and some vacuum line. Tap into the discharge tube, install a bung attach the heater hose, the bypass and route to the intake side of the s/c with the rest of the heater hose. Tie the vacuum line from the bypass to somewhere on the intake. Pretty easy install. I would recommend a bypass no matter how many #'s you see, will help with idle and part throttle applications.....just ask nearly every Novi 1000 guy on here.