I thought I might ask again before calling Vortech.

I'm venting the stock Bosch to the ATM before the MAF but nothing seems to be happening. Nothing vented at idle OR when I rev the car underhood. Vacuum is connected and there is a slight suction on the part of the valve that I thought should be venting.

Am I mistaken or this not how a BPV should be functioning?

Thanks gang, Scott.

 

It should be venting at idle, the diaphragm is probaly bad, if you are going to vent to the atmosphere you need to relocate the maf to the pressure side after the bypass valve.

 

He's right about the diaphragm, but not neccicarily about the MAF location. If you have the MAF upstream (after) the by-pass, then you are ok. It doesn't have to be on the pressure side per-se.

EDIT: You can have the MAF before the by-pass, but you wouldn't be able to vent to ATM. You would have to return it back to the inlet, before the MAF.

 

Unhook the vacuum hose going to the valve at idle and see if you are getting a good vacuum. If its getting vacuum the valve should be opening and a lot of air coming out.

 

Thanks. I figured this wasn't right. The reason I just noticed this is that I put the MAF on the presure side and in front of the bypass.

The valve is most likely junk. This is an early A-trim kit from back in 95-96 with ~25K miles on it.


-Scott.

 

How can you have the MAF after the bypass and not have it on the pressure side? The bypass has to be on the pressure side to relieve pressure so anything after the bypass would be on the pressure side.

 

Read my whole post! I was talking about the bypass RETURN in the part that you quoted.

 

I read your whole post! The part I qouted doesn't say anything about a RETURN. What I originally posted was correct, if you are venting to the atmosphere the MAF has to be after the bypass which is on the pressure side.

 

I called Vortech and someone there seemed to think the vacuum signal was not strong enough to open the valve. Well, I might try hooking up the boost gauge, but I doubt its that. I remember feeling a suction on the discharge part of the valve.....so I'm pretty sure its junk.

Anyone have a cheap valve they want give me .....Vortech wants like $65 for a new Bosch.

Thanks again everyone.

-Scott.

 

I don't need mine anymore, 10.00 plus shipping if you want it.

 

If he doesn't want it I do.

 

breakmyfootoff:

I sent you a PM

-Scott.

 

Ask in a VW or Audi dealer: they cost about $30 new.
The older valve was a little weak, the new ones are better.
New valve:
Bosch part number: 0280 142 108
Audi part number: 034 145 710 C

 

This is something that has kind of been bothering me a bit.

If you've got the bypass venting to atmosphere....won't it actually be sucking air IN rather than allowing air out at idle? The more I think about it, the more it seems this would be the case.

The vacuum from the engine would be holding the bypass valve slightly open (unless there isn't enough vacuum at idle to open the bypass valve? I don't know how much vacuum is needed to open the Bosch bypass valve), and since there is a vacuum condition in the intake system, air would be getting sucked in rather than blown out. At idle, the supercharger isn't spinning quickly enough to provide a boost condition or even equilibrium.

The reason I bring this up is because I'm switching to a bypass valve -> atmosphere setup and I'm concerned that I may need to put something on the valve to filter air that may be getting sucked in through the valve. I don't want it sucking in something large and having it screw up my MAF.

Anyone have good information that will address this theory of mine?

 

The blower always makes more air than what the engine needs.
I checked it with my small 6PSI Vortech (I have an hole for water injection and it always blows out a huge amount of air when I remove the nozzle).
Bigger blowers will bring even more air.

My bypass valve (Bosch) closes at about -3.5 PSI.
At Idle I see -7 / -9 PSI depending on the idle RPM.