shopping for pop off valve
 

I want to add a pop-off valve to my car to protect the engine against overboosts if I kill the wastegate or lose a control hose, etc. I know that a pop off valve is not for boost control in the normal sense, and I hope mine never has to open. But I would like some protection in the event that something goes wrong.

The only one I have seen for sale is from Greddy on rx7.com. Is this a good one? Are there other options available that I should consider?

I am interested in being able to adjust the valve to say 18 psi or something like that, but how can I tell what the setting is? Do I need to boost up to the set pressure and listen for it to open to test the setting, or does it have markings on the valve that indicate the pressure?

I will appreciate any light you can shed on this topic for me.

Thanks,
-Max

i have an HKS one, may be willing to sell it. presure is determined by a screw setting. there is a spring for different ranges inside. the only spring i have is the red one. (=up to 15lb i think)
i have to figure out my greddy typr-R BOV first, i think it can double as a POV if i am not mistaken. if so, you are more than welcome to my POV.

Max

Adjustment to the Greddy type is by physical testing and resetting. (Similar to a Profec B but mechanical rather than electrical).

All POV's may come set initially to one bar over ambient, mine did. The valve is capable of controlling boost from .08 kg/mm2 to 2.0 kg/mm2 (11.38 psi to 28.45 psi) according to Greddy. The way you test and set is to drive the car (watching the boost gauge) to establish a baseline. Of course if the baseline exceeds where you want it to be initially you need to reset the set screw to a lower boost tolerance. The set screw has a stop nut attached to keep it from moving once adjusted. You will have no problem identifying the actuation of the unit. A LOUD pop is heard which is contemporaneous with an unquestionable ( and seemingly catastrophic) loss of power. The first time mine activated I was sure I had blown an apex seal.

You continue testing and adjusting until you consistently activate the valve at the highest boost you want to allow. This should not be a pie in the sky number but instead should be at least 1 or 2 percent (depending upon your own level of anality) BELOW the maximum boost you believe your engine can safely handle or the maximum boost you are willing to let your engine see. If you have an adjustable boost controller, you can easily accomplish this headroom.

In my case, I don't want the new and not yet fully tuned engine to see 15 psi yet, I have left the POV set to one bar. The high boost setting on the Profec B to now set to allow .99 bar (which it does with remarkable consistency). That way, as long as the controller and wastegate are functioning properly, it is nearly impossible to get to the pop-off valve's 1 bar actuation point.

That said, the unit HAS activated a couple of times since I have set it. In both cases the ambient temps were extremely different than those on the day I set the POV. It would appear that the theory that increased boost due to differences in ambient temp can be confirmed by the use of a POV. It also shows that the POV does its job regardless of the variables thrown at it.

Like I have always said, $100 or so to insure against overboost is cheap indeed.

If I can be of any other help, please let me know.


Jeff

Thanks for the info and the offer, but I need to set it higher than 15 psi. I think I would rather just get the GReddy than chase down a new spring for the HKS.

-Max

Jeff48, thanks for the write-up. The setting procedure sounds easy enough. I am glad to hear that the "pop" is easy to identify when it lets go. The GReddy sounds like a good choice.

-Max

It looks like the GReddy valve is a pretty good deal at <$150 with the mounting flange. I searched McMaster-Carr for a generic pop safety valve and didn't find anything that seemed like it would work for less money.

It is kind of weird that pop-off valves seem hard to find at online retailers.

-Max

You might want to give X S Engineering a call. They may be able to guide you to a product that you can buy online.

regards and quite interesting. Maybe a POV is in my future as well.

Rick

I have a greddy one but i didn't install it yet. Do i absolutely need the flange in order to use the pop off valve or can i just sauter it in?

i have the greddy unit installed in my car. I think the hks is a lot easier to be weld on. and it will look a lot cleaner. i had to cut and grind the mount that i bought from greddy, in order for it to fit right so i can weld it in.
Hks look a lot easier to be welded on.
-andrew-

1FookinTiteFD

It is my guess that although you can probably weld the POV (also known as a relief valve) directly to the piping, you gain two things by using the flange. The first is the ease of removing the valve if you need to. If for some future reason you need to remove or replace it, you just unscrew it and screw something else in. The second reason is that the surface area for the weld is larger which always provides better distribution of force.

I personally would recommend against simply welding the unit in place though.


Jeff