Blow off valve question, Please help!

Porsche944parts · 10-29-2007, 07:17 PM

SO I bought a aftermarket blow off vale for my 1986 951 and went to install it today. After a quick simple install I took the car out for a spin and it definatly seems like it pulls a little harder and spools up a little quicker but maybe im just daydreaming.......... Anyways the whole reason I bought the valve was to hear that wonderfull PSHHHHHHHH sound when I will be switching gears at full boost but unfortunatly nothing.
SO now im woundering is it adjusted wrong???? (cause the top of it spins)

OR

Does it only need to be connected in only one of the inlets???
Does it need to be connected to the bottom inlet or the side on the stock piping???
Anyone who knows anything about getting the wonderfull sound please help.
I hop my questions make sense, if the dont I can try to explain better.

2Tight · 10-29-2007, 07:20 PM

It doesn't make that noise because it's actually a recirculating type BOV (diverter valve) dumping back into the intake rather than the atmosphere. That keeps it muffled and allows the turbo stay spooled up a bit between shifts.

Porsche944parts · 10-29-2007, 07:30 PM

SO do you mean you cant put a blow off valve there?? because the piece I bought is a blow off valve, so I dont really understand what you mean.

2Tight · 10-29-2007, 07:43 PM

You can use a BOV if you want but I have no idea what you bought. Many people call the OE diverter valve a BOV. If your new BOV has only 1 large hose and vents to the atmosphere you should get the whoosh you want to hear unless you aren't making any boost. If it has two large hoses then it's a diverter valve and the sound is more subdued. If you use a BOV venting to atmosphere you will need to plug the unused port in your J-boot. They both serve the same purpose, they just function differently.

Porsche944parts · 10-29-2007, 08:14 PM

OK Yes my valve is a blow off valve. It has 2 connections and then a third part the looks like a bell where the air would come from but how do I connect it properly??
I go the part the I need to close off the part in the J tube BUT do I connect that other hose to the bottom of my BOV or the side???

Porsche944parts · 10-30-2007, 09:06 AM

ANYONE know the answer to my last question????

87944turbo · 10-30-2007, 09:34 AM

Who is the manufacturer of your BOV? Some intstall differently than others.

Porsche944parts · 10-30-2007, 09:57 AM

It is made by super power. it is a cheap ebay brand. Here is a link to a picture maybe that will help you determin where i am supposed to hook up what.
link:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&ih=020&sspagename=STRK%3AME WN%3AIT&viewitem=&item=300161100021&rd=1

nynor · 10-30-2007, 11:44 AM

that one says it can be used both ways. if you have two of the connecting ends attached to intake hoses, you are using it as a diverter.

87944turbo · 10-30-2007, 11:46 AM

Looks like a cheap knock off of the GFB hyrbid valve. If it works the same way, it should be routed like this.

Porsche944parts · 10-30-2007, 06:28 PM

how would I route it if I want to use it as a blow off valve??
And as of right now I have the J boot going to the bottom and the intercooler pipe going to the side, did I do it wrong?? the car does run fine with it that way so far.

ae1969 · 10-30-2007, 07:04 PM

Quote:

Originally Posted by Porsche944parts

how would I route it if I want to use it as a blow off valve??
And as of right now I have the J boot going to the bottom and the intercooler pipe going to the side, did I do it wrong?? the car does run fine with it that way so far.

If its the one above you only connect the hose from the intercooler pipe to the BOV. You leave the other end open that vents to atmosphere.

The other hose on the car you have to plug it up. That one connects to the J-boot.

Porsche944parts · 10-30-2007, 07:13 PM

But would you know? do I connect the intercooler pipe to the side of the BOV or to the bottom?? Let me also say the side flange unscrews and there is a plug I got with the BOV but the bottom does not unscrew.

Porsche944parts · 10-30-2007, 08:46 PM

anyone have a idea?

87944turbo · 10-31-2007, 06:43 AM

Quote:

And as of right now I have the J boot going to the bottom and the intercooler pipe going to the side, did I do it wrong??

Yes you have it installed wrong. Can you see the picture I added in post #10? You need to have the side port going to the J-boot and the bottom port to the intercooler pipe.

The valve you have it what is called a HYBRID valve. If you look at your stock Bosch valve you will notice that it has 2 ports. Your Ebay valve has 3 ports. Here is why:

The stock Bosch valve, when it opens, recirculates 100% of the dumped air back into the J-boot.

The Hybrid valve, when it opens, dumps approximately 50% air to atmosphere (Port with the horn or bell) and 50% back into the J-boot (side port).

The reason you have a plug is that you can remove the bell/horn, install the plug and turn you 50% recirculating valve into a 2 port 100% recirculating valve.

Here is a pic of mine installed, not the greatest but at least it shows you the orientation of the BOV.

And for further clarification, if you really wanted a true 100% dump to atmosphere BOV, you would need a bell/horn for both of the side ports. But then of course you would have to plug your J-boot b/c it would be left with a open hole.

I am not even going to get into why it is not recommened to run a BOV with your AFM, assuming you are running one and not a blow through MAF, but there are a variety of reasons that this is a bad idea such as running rich during shifts, poor transient response, etc... If you want to know more I would recommend a search.

Porsche944parts · 10-31-2007, 09:44 AM

Thanks alot for your help!! I have 1 more quick question. if I have it installed wrong then why is the car still running fine?

87944turbo · 10-31-2007, 10:08 AM

Quote:

Thanks alot for your help!! I have 1 more quick question. if I have it installed wrong then why is the car still running fine?

Even though it's installed backwards it must still be able to hold vac. I can't imagine that it would work correctly or work effeciently as it should under boost though. It really depends on the design of the valve. I would think the one you have is a piston type, but I am not sure. When you say running fine, is that fine under idle or fine under idle and boost?

Porsche944parts · 10-31-2007, 10:32 AM

I punched it to full boost and it drove fine. even semmed to pull harder than my stock bosch valve.

87944turbo · 10-31-2007, 11:09 AM

It probably is pulling harder than your stock valve especially if your stock valve was leaking under boost. The real question is whether or not it was relieving pressure correctly when you get off the accelerator quickly and the throttle plate closes. You could still be experiencing compressor surge, its really a matter of whether or not it bad enough that you can hear it.

Have you tried it with the BOV installed the other way yet?

Porsche944parts · 10-31-2007, 07:07 PM

No not yet, I all together put the stock valve on for now because I heard it is really bad for the motor if I am running it at full boost with the valve installed backwards. SO I took it off cause im not sure if I put it on right or not. would you be able to tell from pics what way it needs to be put in?