Blow off valve not opening

volvee850glt · Post by **volvee850glt** » 03 Mar 2010, 20:03

I recently rerouted my intercooler piping and put a GReddy blow off valve on. For some reason the bov is not opening. I tee'd the vacuum line to the line from the manifold to the stock recirculating valve. I even tried putting right on the manifold and blocked off the line to the stock valve but its not working. Can anyone help please?

Thank you.

Post by **vegasjetskier** » 03 Mar 2010, 21:33

Is it adjustable? If so, maybe you've got it set too high.

volvee850glt · Post by **volvee850glt** » 04 Mar 2010, 14:48

Yes and I have as soft as it will go but still doesn't open I even took one of the springs out.

volvee850glt · Post by **volvee850glt** » 04 Mar 2010, 16:01

I have it opening half way but thats only when it is idling and then it dies. I have no idea what to do from here.

Post by **vegasjetskier** » 04 Mar 2010, 17:52

You definitely do not want it opening when it's idling. That will allow unmeasured air into the engine and mess up the fuel mixture. You might want to remove the original valve and put in a bypass or plug. Also, make sure that your vacuum source is on the engine side of the throttle body. If you have connected before the throttle body you will not get the correct vacuum. On my Mitsubishi I removed the original valve and put a metal plug in the return hole. This maintains the tubing as a continuous tract. Then the blowoff valve went on the return pressure tube that had connected to the original valve. This was an HKS valve, so the Greddy may be different, but the principles are the same. Pressure is maintained in the tubes until you let off the throttle, then the intake vacuum pulls the blowoff valve open and releases the pressure.

Post by **vegasjetskier** » 04 Mar 2010, 18:01

Here's a set of instructions for a Greddy valve. Did you do something like this?

http://www.greddy.com/img/PHP/products/pdf/1269.pdf

volvee850glt · Post by **volvee850glt** » 04 Mar 2010, 18:07

But if the manifold is under vacuum at idle is there anything to do because it has the most vacuum during idle

Post by **vegasjetskier** » 04 Mar 2010, 18:23

volvee850glt wrote:But if the manifold is under vacuum at idle is there anything to do because it has the most vacuum during idle

No, it does not have the most vacuum at idle. It has the most vacuum when the engine is revved up and the throttle butterfly is slammed shut (which is also when you want the blowoff to occur to prevent the high pressure in the turbo tubes from backing up against the turbine compressor wheel). This is the same time that you are shifting gears on the track if you are racing, and when you hear the whoosh of the blowoff in turbo cars while you are watching a race.

If you reroute the hoses to get the valve working, put the spring back in that you removed. Did you get directions with your valve?

volvee850glt · Post by **volvee850glt** » 04 Mar 2010, 18:30

No I didn't get instructions and with both the springs there isn't enough vacuum to open it. There isn't even enough to open it all the way with one.

Post by **vegasjetskier** » 04 Mar 2010, 18:35

volvee850glt wrote:No I didn't get instructions and with both the springs there isn't enough vacuum to open it. There isn't even enough to open it all the way with one.

OK, you do understand that it's not supposed to open until you have the engine revved near redline and slam the throttle shut all at once, right? Even then, it will only open for a about a second or less.