Blowoff valve install

The pressure coming through the reference line is equal to the pressure under the BOV piston. Therefore a VERY mild spring will hold it shut just fine under these conditions. Under these conditions, the pressure in your intake manifold is much lower than the pressure in your intake piping therefore under the BOV piston so the BOV has a natural tendency to spring open. Being open isn't even a problem if you are recirculating your BOV into your intake. However if you are NOT recirculating, it can either allow unfiltered air into your intake or push metered air out of your intake which can be a problem.

Using less spring energy will allow the BOV to snap open as rapidly as possible when pressure release is necessary.

There are several ways to do this. Less spring energy means your BOV piston will open easily. More spring energy means it will be harder to open and more resistant to opening during high-vacuum conditions.

Your goal is to have the lowest amount of spring energy that keeps your BOV closed during high-vacuum conditions. You can do this by purchasing a lighter spring from a hardware store, or by cutting the lightest spring that comes with the BOV.

Note: this is not a defect with the BOV! Some cars pull very little vacuum and need an especially light spring. If this is the case on your car, venting your BOV to the atmosphere can result in an inaccurate count of the air entering your engine, resulting in a rich condition after each shift, damaging performance. On some cars it won't be noticeable, but on some cars it will cause the engine to stall instantly. If this is the air metering method in your car and you want the "PSSSHHHH" noise, you would be better off installing an open-element air filter, since it is the airbox on most cars that stifles the blow off noise.

If this does not give you the desired effect, you might try changing your BOV to one of our aftermarket BOV's that is capable of recirculating to the turbo inlet pipe. If you are recirculating, it is technically correct to call it a CBV not a BOV, although the industry has made the terms synonymous. Theoretically, you can actually hold more boost if you are not recirculating. When you recirculate, the BOV outlet recirculates into the pre-turbo intake pipe. During acceleration, the pre-turbo intake pipe is under vacuum.

This is what causes some BOVs to leak at lower boost than our website recommends them for. There is an aspect of truth to this, however a BOV is a very simple product once you understand it and all of them work pretty much the same way.

Our website has recommended boost levels listed for each of our BOVs. The typical point of failure on a BOV is the membrane that allows the piston to move.

Either it will leak at the seal or it will rupture causing the BOV to always leak under boost. We take this point of failure into consideration when recommending boost levels for our BOVs. Another cause of BOV leakage is the seal at the bottom of the piston. This is a temporary seal that has to break instantly and easily during pressure release yet be strong enough when closed to prevent boost leakage.

We also take this point of failure into consideration when recommending boost levels for our BOVs. One thing that is important is the issue of BOV volume. Think of it as drilling an instant, temporary hole in your intake piping. Installing a blow off valve gives the air a place to go and relieves pressure from the turbo's compression wheel during gear shifts when the driver's foot is off the accelerator.

Open the hood and disconnect the negative cable from the battery terminal. Disconnect the positive cable from the battery terminal. Locate the factory recirculating valve. Use your shop manual if you need a visual description for the valve specific to your vehicle. This valve recirculates the intake air to the exhaust.

This is the device we want to replace. There will be two hoses connected to vacuum lines. The top vacuum line is connected to the throttle body after the intake. This vacuum pressure is what makes the valve operate.

Use either a screwdriver or socket wrench either should work to remove the screw bolts on the hose clamps. Slide the hose clamps out of the way and use the screwdriver to pry both the vacuum lines off. Install the new blow off valve.