Trying to determine the type of valve is on the outlet pipe from the S/C.
Is a blow off valve or a bypass valve, it is a Bosch, does anyone have a part number?

 

Do you see the part in this picture? Is it the item with the small air filter attached in the bottom center of the picture?

 

I have the plastic Bosch one, but I have heard they are failure prone (mine has been fine). Part number is 951-110-313-00 but it has been discontinued.

Here is the metal one that has superseded the Bosch one on Pelican.

http://www.pelicanparts.com/cgi-bin/...rger%2C%20Each

 

That's a bypass valve. The 1.8T (VW) guys upgrade to the metal one as the plastic models fail fairly often. It has probalby more to do with the location (at the firewall) than the part itself.

I'm running one 300ZXTT and another 2.2L Dodge turbo bypass vavle. The more you can vent the better it is for SC belt. I think the Bosch is on the small side.

 

The one with the filter but I do not have a filter.
My question the way it is attached going to free air would this not let un-metered air into the intake tube going to the Maf?
I have a nipple I welded onto the intake S/C airbox and was advised to return the bypass valve back into the S/C air box.

 

Did you put your Maf back in the stock location? If you did then yes put the BOV back in just after the SC outlet, and since you now have a port there, you can connect the exit tube of the BOV to the airbox. While the intake is under vacuum it just bleeds off pressure from the SC and there is no way it will let false air into the MAF.

 

Mark, if the valve is before the MAF then it isn't unmetered.

 

It is back in the stock location.
The kit has it going to free air!
I want to go from the bypass valve connection located on inlet pipe to the Maf that comes from the S/C back into the S/C airbox. I have added a nipple welded to the S/C airbox inlet and see what happens. I think we are talking about the same bypass routing, just stop venting it to the air. This creates a loop and should not allow un-metered air into the Maf.

 

Technically, it's a bypass valve, but people also very commonly call them blowoff valves, even though they really aren't.

That small air filter in the picture just happens to be laying next to the valve. That filter is not part of or connected to the valve, like the picture might make it appear.

There are other valves that look like the black plastic Bosch ones, but are made by a different manufacturer. I can't remember who Tim said the other manufactuer was, but they're supposed to be more likely to fail than the Bosch made ones. The valves currently being supplied with the Murf kits are black anodized aluminum Vortech Maxflow Racing ones.

If everything's installed like the kit's supposed to be, any time that the engine's running with vacuum in the intake manifold, the valve should be open, and air from the supercharger blows out of it. When there's no vacuum in the intake manifold, the valve is closed, and no air goes in or out of it. There's never a time when air goes into the intake tube from the valve. Even if there was, it wouldn't be unmetered air. No air is metered air until it's gone through the MAF. The only thing that routing the bypass valve back into the S/C airbox instead of having it vent to the atmosphere would do is quiet the sound that the valve makes when it releases air.

 

Unbelievably, I have 5 of these things installed on my twin turbo installation it took me about 3 years to work out that this was what was required to get a smooth return to idle !

It is all part of the trade off for having boost at 1800 rpms .....

Cheers Roy