I just finsished up my FMIC for the vortech and I moved my MAF from preblower (bypass) to post blower so I could run it as a blow off. When its idling, should I feel air coming out of the discharge of the blowoff?? I havent messed with the spring, but I want to make sure everything is working as it should before I start throwing a ton of boost at it. Im waiting on a new nozzle holder so the meth isnt on and I dont feel comfortable getting into it just yet. Is there any way I can make sure its working?? Im using the maxflo from vortech. Thanks
I'll get some pics in the next couple of days. Im pretty happy with it though.

 

When you give it some throttle and the vacuum goes to 0, the blow off should close and force all the air into the motor. Then when you let off the throttle and create vacuum, the valve should open letting the excess air pressure escape. Should be able to do this just revving in neutral. As long as it is before the MAF, you should be fine.

 

I agree with KBRacing, the BOV should vent under high vacuum conditions ( like at idle ). This way if you are under heavy throttle/boost and shut the throttle off quickly the built up pressure in the intake tract will vent out and not slam backwards into the blower compressor. It makes an unusual sound when it happens but is hard on the compressor wheel and shaft.

 

The way the STS sytem works is to vent when you see 11# of vacuum. The TiAL blowoff has a 11# spring in it. When you are at idle the valve should be closed and your engine should see about 9# to 10# vacuum. When you accelerate from a stop or you are just moving slowly you want all the air available to the engine. When you are moving a little faster and let off the throttle completely you will see about 11# to 12# of vacuum and the valve should open and vent off. This will help to keep the turbo/centrifugal spooled up and relieve boost pressure from the throttle plate and compressor/turbine wheels. If your valve is vented to the air you should be able to hear a kind of a puffffttttt sound as the air is expelled through the open valve.

You will definately see the benefit when you lift suddenly at the end of a 1/4 WOT run or when you shift a manual transmission. You have to lift completely off the throttle for the blowoff valve to open or at least till you see 11# of vacuum and you will probably only be able to hear it when the boost is up quite high and there is a lot of pressure to vent off. If you just ease off the throttle after a WOT run, as when on the highway, the valve will likely not open or if it does the boost pressure will have dropped enough so that you will not hear it open.

A 9# spring is availble for people at higher altitudes that see less vacuum due to decreased atmospheric pressure.

The only time I hear my blowoff valve vent is if I lift very abruptly after a WOT run. I don't do this often as I just tend to ease off the throttle when I am on the street and listen to the the tubrine squeal.