New 2 the SC... Bypass Valve & Boost Gauge Question

rallystang

Registered User
Hey everyone. I just did a M90 Swap and have a couple questions.

First of all when I shut my car off, after a few seconds the Bypass Valve lets out a NASTY 5 second scream when it is closing. I have the vacuum to the bypass running off of the... Tube that bolts directly to the lower intake, their is a vac nipple on the back drivers side that I am using. Is it connected in the right place? Is it normal? Does it need some Grease?

Second, where does the stock boost gauge get its Vac/Boost reading from.(the one I'm using for the Bypass Valve?)

Thanks!
 
I do not have a vacuum routing right in front of me, but I think you need to have the bypass valve vacuum line hooked up before the supercharger. If you have it hooked to the lower intake, aren't you feeding it pressurized air?
 
Yes, sometimes it sees +psi, but in those cases it would be held closed by the pressure(this is my thoughts when hooking it up). 90% of time the entire system sees a vacuum, therefore the valve would be held open unless I'm on the gas in a boost situation.

Thanks for the tip though, I'll try feeding it some vac from the TB.
 
Last edited:
Actually it's vacuum that holds it open and the lack there of that closes it to boost.

Sounds like either the valve(inside the intake) or the vacuum canister itself could be sticking.
 

Attachments

  • vacuumroute.gif
    vacuumroute.gif
    60.5 KB · Views: 126
Thanks RBH, your diagram is sure to help. Sounds like 'lack there of keeps it closed' so maybe I'll try a vac source further from the lower intake itself.


Still curious on the Stock boost gauge vac source.
 
Last edited:
I think you want the bypass valve ("ABV" in the diagram) to the TB, like you said. I think the boost / vacuum gauge probably goes where you had the bypass hooked up until now.
 
Back
Top