From what I understand, a 50/50 vents half into the intake, half to atmosphere. It makes some noise, but doesnt swing as rich. Someone told me that typically these are set up sequentially, so that on light vents, it dumps 100% back into the intake. This is so that at light boost/part throttle you get no rich condition and either no or less noise.

At higher boost, the valve opens all the way, and dumps into the intake and atmosphere. Is this correct, and is it something thats good to have. Im running 12 psi of boost and may end up going higher to around 16 or 18 in the future.

 

I haven't researched the actual type or application of blow off valve you are referring to, but I have considered the thought process. Not sure what your setup is, but I too am going to be increasing boost levels which will in turn be increasing the venting volume of the blow-off-valve, yielding even more charge over-calcuation by the ECU and a brief rich burn. Right now it is more of a nuisance than a probem, I don't notice any hesitation or misfire immediately after a large venting volume 99% of the time, but I do get a little hiccup every so often 1% of the time. Also when on the track, I do not like to think about all the combustion cycles I've been forcing my engine to burn at en extremely rich mixture producing lots of carbon deposits to foul my plugs, overheat my catalytic convertor, and cover the entire system in a black soot.

Personally, I think the best course of action would be to correct the root source of the problem, rather than going out of your way to fabricate a "fix-it." Switch to a manifold absolute pressure sensor (and associated ECU) and problem solved! Your fuel calculations are then based off of constantly monitored manifold pressure, which will correctly detect the change that occurs when the blow off valve vents, unlike a mass air-flow sensor.

 

sorry for inserting a noobish question - but does increasing the boost require adjustments to the BOV to accomodate the change in pressure - to allow more into the intake rather than atmosphere?

 

Generally not, as the BOV only opens when there is vacuum in the intake manifold.
If you have a cheap BOV, too much boost could cause it to leak, but it would still intend to be closed.

And I agree with getting a MAP based ecu to solve the MAF issue.

 

...and a vacuum is created when the TB closes, right? Thus releasing the air held in the tubing?

Sorry, I'm not trying to hijack, I'm trying to understand why you'd have it dumping into the atmosphere at higher boost.

 

The main reason why the so-called 50/50 BOV's came into existence is when people are using piggyback ECU's to tune a turbocharged engine that used to be N/A. Whether your MAF or MAP at standalone ECU won't have any issues venting 100% to atmosphere.

With that said if your using a piggyback to tune your ride and your MAF then you NEED a BOV that sends a certain amount of the pressure back into the intake tract otherwise you'll have issues everytime you shift. Now how much you send back depends on how much your stock ECU likes. Most N/A ECUs don't like a sudden complete loss of airflow when you shift and cause a dangerous lean condition. Most N/A ECUs will be fine with a 50/50 mix, but you need to watch and log your AFRs to make sure things are not getting too lean or rich.