87RX7TII

I've just repaired a few things on my car and after a month of the car sitting its finally finished... Obviously I want to try to start it up.

I installed 2 new injectors along with a custom TID, I blocked off my ACV and EGR valves, and my air pump is gone since I have a full exhaust.

The only thing I need now is a swing valve for my stock BOV, BUT since its Sunday the stores are closed and I'll have to wait until Monday to pick up my much needed piece.

My question is... is it SAFE to try and start it w/o a functional BOV.
I want to try to tune it so I can just throw the part on tomorrow and take her out.

I think since the BOV is hooked up but not plumbed back into the TID this will allow unregistered air to sneak in, faulting all of my tuning efforts..

Is this correct?

MARTIN

First of all, a BOV is sort of like a check valve. Air can only travle one way...unless off course its faulty... anyways, I started and idled my car with no BOV in place...
It doesnt really matter at idle. Go ahead do what you gotta do and keep the revs bellow 3k...

ilike2eatricers

I had to limp my car home with no BOV about 10 miles from my body shop. It was fine and had no problems, just make sure you dont go into boost. I'm not sure what a swing valve is but if you have a vac leak you can just plug it up for now to get home or whatever. I wouldnt tune it though until you get the part you need.

n4ji

iTrader: (1)

With out keeping vaccuum pressure it'll ruin the turbo. This is why the BOV only lets air out, not it. If you do drive without one, DO NOT BOOST and you should be fine.

87RX7TII

I installed a one way check valve in front of the stock bov ...
Should this work as a "ghetto bov?"

Aaron Cake

iTrader: (1)

There seem to be a lot of people who don't know how a BOV works...So let's get some thing straight, OK?

The function of a BOV is to vent compressed air when the throttle plates snap shut. When the valve sees vacuum, it opens a valve and vents air from the compressor out to the atmosphere. If it vented air back into the intake stream (in the case of the FC, to just after the AFM) then it is called a Bypass valve.

This is done to prevent compressor surge. When the throttle plates snap shut, two things happen. The first is that a shockwave of pressurized air is sent back through the piping/intercooler to the compressor of the turbo. This wave hits the turbine hard, and can slow it down by 50,000 RPM or so. It puts extreme stress on the bearings. You can actually hear this in cars that have no BOV or one that is not properly adjusted. When the driver takes his/her foot of the throttle, you hear a "phaser" type sound...That is the wave moving back and forth.

The second effect is called surge (or sometimes stall). With no where for the air from the compressor to go, the compressor stops doing useful work (you can only pack so much air into a space) an dbegins to spin freely. This overspeeds the turbo by 50,000 RPM or more, which is again very bad for the bearings and seals.

That said, the stock FC bypass valve is designed in such a way that it leaks at idle. So if you just open vent it, the valve will draw in air and become a huge vacuum leak. This is why a check valve is necessary. However, the whole modification is pointless. You gain nothing, and all you are doing is restricting the output of the bypass valve with your check valve. So the best bet is to plumb the valve back into the intake as it is from the factory, or get a BOV that is vented to the atmosphere.

Now, as long as you're not hitting any serious boost, it is fine to drive without the bypass valve as long as the vacuum leaks are plugged.