Greddy Relief Valve

[65Cobra]

I'm having trouble finding a reliable (mail order) place to purchase the Greddy Adjustable Relief Valve #11501710... either they don't have it in stock or they want an arm and a leg to ship. I live in PA... any suggestions? Thanks.

 

[cdhoroho]

if you have a bov why use the relief valve
what exactly are you using the relief valve for?

 

[65Cobra]

They serve two completely different functions...

The BOV opens during full throttle lifts which is why the internal spring is based on idle vacuum. When you lift off the throttle, the throttle plates suddenly close and the air pressure has nowhere to go. The resulting backpressure to the turbo can cause compressor surge, compressor backspin and turbo stalling which can damage the turbo. The BOV helps relieve backpressure which reduces engine stress, prolongs the life of the tubo and even shortens boost recovery time when you open the throttle again. But one thing it does NOT do is prevent over-boosting.

That's where a relief valve comes into the picture because it prevents over-boosting. It functions like a wastegate so it's similar to having a second wastegate, only this one is mounted to the plenum. The spring in the Greddy Relief Valve is adjustable and is normally set 1-2 psi above the setting on your wastegate. Should the pressure in your plenum exceed the setting on the relief valve, it will open and allow the excess pressure to escape. A wastegate should be sufficient but there can always be a problem, like boost creep.

Hope I explained this okay.

 

[cdhoroho]

They serve two completely different functions...

The BOV opens during full throttle lifts which is why the internal spring is based on idle vacuum. When you lift off the throttle, the throttle plates suddenly close and the air pressure has nowhere to go. The resulting backpressure to the turbo can cause compressor surge, compressor backspin and turbo stalling which can damage the turbo. The BOV helps relieve backpressure which reduces engine stress, prolongs the life of the tubo and even shortens boost recovery time when you open the throttle again. But one thing it does NOT do is prevent over-boosting.

That's where a relief valve comes into the picture because it prevents over-boosting. It functions like a wastegate so it's similar to having a second wastegate, only this one is mounted to the plenum. The spring in the Greddy Relief Valve is adjustable and is normally set 1-2 psi above the setting on your wastegate. Should the pressure in your plenum exceed the setting on the relief valve, it will open and allow the excess pressure to escape. A wastegate should be sufficient but there can always be a problem, like boost creep.

Hope I explained this okay.

i knew what it was but tryin to figure out why you would put it in there
those are more for superchargers
if the wastegate is designed right it wont over boost unless you have a malfunction

but the relief valve will hurt the turbo cause if you open the plenum under boost and cause the turbo to over spin (due to no resistance and you will spit a turbo (hurt it)
i have had a few turbo kits and the one i have now is good to just under 700 hp and there isnt a single relief valve on mine
we build all our here and i honestly wouldnt ever put a relief valve on a bike kit

ill repeat if you open it up you have a very large chance of hurting the turbo

 

[GPW]

In stock just call.........

 

[smithabusa]

I agree with horo, maybe a good idea in theory, but unless you know if its active or not you can overspool the crap outta the turbo (just like a real bad boost leak) and hurt the turbo.

Maybe an adjustable hobbs switch set slightly over wastegate spring running to a superbright LED like i use on my shift lights as a warning light.

Greg

 

[65Cobra]

The reason for installing the relief valve has to do with my setup. The bike is a 99 Busa with a Mr Turbo kit that was installed in October 2000, taken on a couple test runs, and put in storage where it remained due to medical problems. Those early kits had numerous problems so my goal is to update every component associated with the original kit. I'm currently fabricating a new plenum from aluminum and once finished, all that will remain are the header, turbo, wastegate and exhaust, which will be replaced next summer. The relief valve was being used as a precaution.

Since the relief valve only prevents over-boost, it only remains open as long as pressure exceeds the setting, otherwise it closes again. Since pressure is never reduced to anything less than what was originally intended had the wastegate done it's job, I don't see how turbo over spin can ever be an issue.

 

[smithabusa]

If you are maintaining the same boost level with a hole in the intake track the turbo has to spin harder to do so. Heat becomes an issue, you start overworking the turbo to get the same boost level and can tear it up.

 

[GPW]

Properly adjusted the BOV will only leak or release pressure during off throttle or vacum signal. We have seven 30 psi bikes using this BOV and it works flawlessly. Reduces surge on compressor and reduces on throttle off throttle lag. Call Greddy and speak with their tech's a wealth of knowledge there. They work great on high or low boost applications. Should be adjusted on the dyno to be sure they do not crack under intended boost pressure.

<center>

</center>

 

[65Cobra]

Not sure if this matters but the point was not to use the Greddy Relief Valve to compensate for an inadequate wastegate, but just as a precaution in case something fails. If I found an issue with the wastegate, or the relief valve activated on a regular basis, I would stop using the bike and fix the problem. Also, I had already decided to connect a Hobb's switch to an LED so I would still have a visual warning to back off the throttle.

Otherwise, it's getting to late for me to think straight so I'm off to bed. I'll contact Greddy tomorrow. Thanks.

 

[cdhoroho]

if you over boost a turbo (over spin it with no resistance) it will trash the bearings then possible break the wheel
if it breaks the wheel it could get into the motor and that isnt a good thing

their are many other options and i honestly would never put a relief valve on a turbo kit


you could go with secondaries and set the fueling to go wide open if over boost occurs would would cause the system to stop creating boost

i would rather go that route then a relief valve

 

[OZBooster]

Its not uncommon for car manufactures to have a relieve valve in the system, and if the wastegate is working properly it may never get used, if not its not going to let the turbo overspeed as much as a open hole, as the plenum pressure would be maintained . considering the carnage that can be caused with overboost i think its a reasonable option.

 

[turbobusa2000]

Is this relief valve in question here the same as a HKS Super sequential blow off valve? Or something different?

 

[65Cobra]

cdhoroho, something along the lines of wide open fueling in the event of overboost is a good idea but not if it means expensive mods to my setup after I just finished updating the entire fuel system with a Bosch 044 pump, BEGI FMU, etc. So, is there anything I can connect a Hobbs switch to, that will prevent overboost without putting myself at risk... i.e. killing the engine would be disasterous.

OZBooster, that pretty much summarizes how I feel about the relief valve.

 

[65Cobra]

turbobusa2000, the relief valve is not the same. Although the HKS uses two valves, one primary and one secondary, which operate utilizing a different design, it's function is still that of a BOV, and therefore will not prevent over-boosting. So Post #3 above applies to the HKS along with any other BOV.

 

[turbobusa2000]

turbobusa2000, the relief valve is not the same. Although the HKS uses two valves, one primary and one secondary, which operate utilizing a different design, it's function is still that of a BOV, and therefore will not prevent over-boosting. So Post #3 above applies to the HKS along with any other BOV.

Thanks, that answered my question!