but now the extra pressure in the INTAKE system will prevent MORE air from passing the MAF
.. further up the line.
Think of it this way, once the BPV dumps air back into the intake, the VACUUM is less after the MAF, so less air will pass the MAF.
in fact, if what Don says is true, and if under HIGH BOOST applications there is enough BPV pressure to blow intake hoses, presumably there is NO longer vacuum after the MAF, meaning air will flow back PAST the MAF backwards, further screwing up the MAF readings.
"It's easier to practice medicine without a license in this country than it is to get info on tuning Motronic." -JasonS9
Naw, the car runs rich in essense because say for example you take your Forge valve
and disconnect the part that goes back into the intake, and plug that hole - now the vacuum is holding the valve open a bit, so its causing the air to go right into the atmosphere. The car begins to run rough because the system is no longer 'pressurized'... so to circumvent such issues, a stiff/adjustable spring will allow it to stay closed under idle vacuum, causing the system to stay pressurized, and the ECU should adapt accordingly - otherwise you're just having arrant amounts of air fluxuating out of the valve. For instance, if you take your forge valve, and unplug that one end - and put a stiff spring in the forge valve, and used washer's to help adjust when the valve opens (under how many hG's of vacuum) you could make the forge's work as a BOV - the downside to this as some of us were discussing last night, is unless you use a very stiff spring - and use washers or what not to compress the spring some more, you lose some piston travel on release which may or may not be bad. It still opens more than a stock BPV...
The car will run correctly though - a simple test is to open one end of your valve, and tape the end closed, you will notice that your idle will be perfect (do NOT make boost while you have the tape in place).
for styles like the greddy typeS or turboXS type H-25 - they simply plug into where ur bpv is.
for styles like the hks ssq, and "other" turboXS one (the one on the right of don's post) - you need to get a little more creative and get a adaptor or a custom flange. you could also mount these on ur ic return hose (you'll need a custom pipe with the flange welded on), this will run in conjunction with your bpv.
email me if your interested in the second style with the hks, i believe we have a few kits still on the shelf.
A couple of things if I understand what you're saying. When it dumps back into the system it's not getting metered again. It's all behind the MAF at this point. Also because the BPVs are open (vacuum in manifold) it just continue to circulate until the throttle plate opens again. If for some strange reason the air did flow back out the intake (maybe the BPVs are malfunctioning?) the MAF is capable of reading return air flow. What it does with these reading I do not fully understand, but it is capable of it.
2004 4.2 Allroad
2000 2.7t S4 <a href="http://www.azaudi.org/">
The Arizona Audi Car Club</a>
Click picture for specs.
The Audis run extra fuel (rich) to lower the exhaust gas temps, removing air and causing the car to run richer has been known to generate engine wash (washing the cylinder sidewalls with fuel) Are you saying that our cars run lean enough for that not to happen? I know Supras and other turbo charged cars have been prown to that when their boost is vented to atmosphere.