In case anyone is interested, I have found a very inexpensive alternative to the $120 Greddy pressure relief valves:



Good ol Grainger has a nice high flow relief valve for $30. It's fully adjustable from 0-20psi and has a 3/4" NPT inlet (the Greddy is 1"). The part number is 5Z765 and they operate at temps (i.e. underhood) up to 250F degrees.

Here's a pic:


For most sub-20psi setups, they should easily flow as much cfms as the Greddy valve. The Grainger valve flows 54CFM and is 3/4" NPT and adjusts to 20psi; the Greddy valve adjusts to 30psi and is 1" NPT. I do not know exactly what the Greddy valve flows but I believe it's only 1" NPT because it has to flow to 30psi. So the Grainger valve should do just as well up to 20 psi IMO. Remember, the relief valve only has to relieve the EXTRA pressure over what you have it set at...in other words, if you have it set at 10psi, and you overboost to 13psi, it only has to relieve 3psi. So in other words this thing can handle most situations with ease.

It's about 3" long and is easy to install. You just weld any 3/4" pipe fitting from Home Depot (elbow fitting works great) onto your charge pipe, and screw the relief valve right in after setting it.

To set it, you can hook it to an air compressor and use the air compresor regulator to supply a very low pressure of air (since most compressors generate 120-160psi of air). To get the exact setting, you can "T" in an old tire stem valve and read the pressure using a good tire pressure gauge. Just screw the adjuster while reading pressure on the tire gauge - the relief valve will 'pop off' when the desired pressure is reached. Then tighten the lock nut and you're good to go.

BTW, I don't know why more people don't use pop-off valves. It's a cheap way to save your engine in the event of creep/spiking or vacum line popoffs or general screwups. You just set the relief valve to the "max" boost you EVER want your engine to see (say 12psi on a stock motor), and if the boost ever reaches that level, it cuts it off and doesn't let it raise above that limit.

No, I don't have pics. It was more for a heads-up for people interested in an inexpensive pop-off valve.

Here's a little more info from Grainger http://www.grainger.com/images/catalog/2791.GIF

- Slater


[Modified by Slater, 4:19 AM 9/2/2002]


[Modified by Slater, 4:21 AM 9/2/2002]


[Modified by Slater, 4:31 AM 9/2/2002]

 

daymn that sounds good! has anybody used this and have pix??

 

The sucky thing is that I only found out about this after breaking down and getting the Greddy valve. Since not many people use pop-off valves, and even less use the Greddy it was hard to get ANY info on exactly how they work and details such as mounting, setting, etc.

So I got the Greddy and found out just how stupid simple they were. It's basically just a fancy anodized alum version of the Grainger valve. Luckily I only paid $90 for it instead of $120. But when I got it and saw how simple in design it was, and then found the Grainger valve that is the same damn thing for $30 I had to pass on the info!

- Slater

 

Good info.... anyone else use this ??? bizuummp to the tizzop

 

theyre $15 at lowes

 

I have one of those. I also got an aluminum "coupler" which I sawed in half, to weld onto my intercooler for mounting the ugly thing. The internal piece which holds the pressure is nylon, with a rubber oring seal. These internal pieces are only rated to 250 degrees. I'm not sure if this will be a problem, but if it is you could always fab up a metal valve and use a viton o-ring.

The valve is also reversable, as it has two opposing 45degree seats machined into it. Reversed you can use it as a "vaccuum release valve" to allow air to get to the throttle body without passing through the turbo first (air bypass valve). Just mount it right before your throttle body with a small filter on top, and you've got a direct air intake source. I'm not sure yet, how much this would reduce lag, if at all.

 

that sez 25psi to 100.

does it go lower?

 

i did the same as you, read the wrong line. takes a second to disect that page.

How do i order from them?