2 questions about blow off valves
 

1. How can you tell if your BOV is leaking?

2. 3 different people have told me that certain BOV’s will cause the car to run rich and when you get it tuned, to make sure this is taken into consideration. Can someone tell me which ones will cause the car to run rich?

1) Do a pressure test and you should find it easily. Symptoms would be unable to hold target/set boost.



2) Depends on if you're MAF or MAP based. I don't know of it to happen with MAP based, for MAF it still depends. It's not a constant running rich just so you know, what they are referring to is when you back off the gas and the blow off opens for a short period you can have a rich condition if it is a vent to atmosphere type blow off valve on a MAF engine with the BOV placed between the throttle body and the MAF. To avoid this temporary rich condition you'd either need a vent to intake type BOV (also called a bypass valve I believe) or to place the MAF between the throttle body and the BOV. That's the best solution for that issue and if not that way then you may need to compensate for it when you back off the throttle. The effect can be mild and tolerable to causing the engine to cut out sometimes.



The solution I gave should avoid having to mess with the tune.

A BOV usually leaks under two conditions:

-The diaphragm is punctured or not installed properly

-The pressure in the charge pipe exceeds the combined force of the spring + air signal going to the BOV (that is if you're running a push type BOV, ie: Tial, Greddy, or stock in many cases).



If your car is equipped with a MAF sensor (only) to calculate air flow, then your car will run rich (idle rough or stall) if your BOV is being vent to atmosphere AND located between the MAF and the Throttle Body. Best solution to fix that would be reroute the BOV discharged air back to the intake, before the MAF sensor.

As long as the BOV is before the MAF your fine. I ran mine in the stock location, under pressure, with the BOV just before the inter-cooler and it worked fine.



As long as the metered air is not being vented all is good. Thats were you run into problems. The ECU is calculating a certain volume of air via the MAF, but if you vent some of it after it passes the MAF the ECU has no way to know that, so it injects fuel for that calculated amount. When that happens you have less air than expected, so you go pig rich and may even stall the engine.