Greddy Type RS BOV Boost Leak

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LPime001
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Greddy Type RS BOV Boost Leak

Post by LPime001 »

I need some assistance/suggestions.

I’ve been running a recirculated Greddy Type RS for the last few months. When I first installed it I did a pressure test, which it passed, and drove the car for about a week. I was getting pretty bad compressor surge, so I went ahead and did the single spring mod. Below are a couple of links for those curious about what this is.

http://www.evomoto.com/tech_info.php?tPath=1&tech_id=7

http://www.sr20forum.com/turbo/169093-h ... issue.html

The mod completely eliminated the compressor surge, but now I could not hit full boost. I did another pressure test, and discovered a pretty bad boost leak from the valve itself. I guess the single spring is not strong enough to hold the valve closed when in boost, and air is pushing through.

So my question to you guys is which is the lesser of two evils.
Should I fix my blow off valve leak and live with compressor surge?
or
Should I let the valve leak and use my MBC to get the 9 pounds I should be seeing from my wastegate spring? This option would require my turbo to work a lot harder than it needs to in order to generate the 9 pounds I want.
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240sxfan6882
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Post by 240sxfan6882 »

I am using a recirculated Greddy type RS BOV and have absolutely no boost-building problems.

The only thing that I did is that I removed one of the 2 (the small one I believe) springs from inside the housing and left the BOV at the softest setting, and that's it, It works flawless.
The valve stays open during idle and cruising, which is what you want so that you eliminate any surge, but at boost it shuts tight. I've seen 16-PSI on mine without a hiccup. I had mine connected to the brake-booster vacuum line. I removed the vacuum line to test it out and I had nasty surge at that point.
Upon boosting and shifting it's just a loud WOOOSH-sound... even though it's recirculated it's loud, but no flutter at all.

:P
LPime001
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Post by LPime001 »

240sxfan6882 wrote:I am using a recirculated Greddy type RS BOV and have absolutely no boost-building problems.

The only thing that I did is that I removed one of the 2 (the small one I believe) springs from inside the housing and left the BOV at the softest setting, and that's it, It works flawless.
The valve stays open during idle and cruising, which is what you want so that you eliminate any surge, but at boost it shuts tight. I've seen 16-PSI on mine without a hiccup. I had mine connected to the brake-booster vacuum line. I removed the vacuum line to test it out and I had nasty surge at that point.
Upon boosting and shifting it's just a loud WOOOSH-sound... even though it's recirculated it's loud, but no flutter at all.

:P
I went back and redid the blow off today. I originally had the softer spring installed, but i swapped it with the stiffer spring like you did. I also discovered and plugged a pretty large boost leak which must have developed within the last couple of months.

Everything is working great now. The turbo is spooling a lot quicker, and the BOV seems to be working properly. The blow off is a lot louder, and there is no compressor surge at all.

I'm still a bit confused because even with this setup, the BOV leaks during boost leak testing. I guess the BOV seals tightly during boost while driving, but not while testing.

Either way, the car feels much better now.

Thanx
Turbonetics 50 Trim T3/T4 .63ar
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240sxfan6882
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Post by 240sxfan6882 »

The BOV can lean during a boost leak test if enough pressure is placed on the valve to push it up, and no "counter pressure" to keep it shut. Under boost the vacuum-line becomes a boost line; at that point you will have x-psi pushing up against the valve to open it, but you will have an equal amount of force coming in from the vacuum line to cancel it out and keep it closed - that's why it seals under boost (this is all as far as my knowledge goes so anyone is welcomed here to debunk it if it's wrong lol).
dzaster
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Re: Greddy Type RS BOV Boost Leak

Post by dzaster »

I've been having some idling issues so I made a checklist of things to try/change/address. One of those things was to do a vacuum leak test on my vacuum block/tree. Found that my NRG FPR and Greddy RZ BOV leaked pretty bad through the adjustment screw and nipple threads where the jamnut is used to allow adjustment. I put teflon tape on them and vacuum now holds solid.

And the above post I believe is correct. In boost the pressureized top portion of BOV diaphram will assist the spring in holding boost pressure against valve so just pressurizing only your IC piping without pressurizing BOV nipple isnt accurate way of testing BOV's ability to hold boost.
LPime001
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Re: Greddy Type RS BOV Boost Leak

Post by LPime001 »

dzaster wrote:I've been having some idling issues so I made a checklist of things to try/change/address. One of those things was to do a vacuum leak test on my vacuum block/tree. Found that my NRG FPR and Greddy RZ BOV leaked pretty bad through the adjustment screw and nipple threads where the jamnut is used to allow adjustment. I put teflon tape on them and vacuum now holds solid.

And the above post I believe is correct. In boost the pressureized top portion of BOV diaphram will assist the spring in holding boost pressure against valve so just pressurizing only your IC piping without pressurizing BOV nipple isnt accurate way of testing BOV's ability to hold boost.
I completely agree with 240sxfan6882 explanation of how a blow off valve is supposed to work. When I conducted my boost leak test, the signal line was connected to the blow off.

I think i have a restriction in my intercooler. It seems as if the bottom of the blow off (IC piping) pressure is much higher than the top of the blow off (Intake Mani) causing my blow off to remain slightly open during a boost leak test, and during boost.

I actually reinstalled the second spring and re conducted the boost leak test. With both spring installed, I have no leak from the blow off. I do have to deal with a bit of compressor surge, but at least I build boost quicker and can actually hit wastegate spring boost pressure.

Another item that seems to prove my intercooler restriction is the activation of my wastegate. I can hear my wastegate open when my boost gauge reads just below 0, which means my wastegate is seeing a few psi more that my intake mani. I would think my wastegate would open when my gauge read at least a couple of pounds.

Unfortuanately, I haven't had the time test my theory.
Turbonetics 50 Trim T3/T4 .63ar
JGS Log Mani & Downpipe
Turbonetics Wastegate
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dzaster
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Re: Greddy Type RS BOV Boost Leak

Post by dzaster »

Anybody running recirculated find the BOV no longer holds boost like it did when it was VTA? I believe this is what is now happening. Will hit 10psi for a blink then down to 7psi. No changes made to EBC or system for that matter. No new boost leaks besides a throttle body shaft leak that was present always. Spring tension is cranked down too.
ViperGT
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Re: Greddy Type RS BOV Boost Leak

Post by ViperGT »

that would make no sense unless there was vaccum on the blow off side, you want the bov adjusted so that its closed at idle as well, esp if you are VTA as you are sucking/blowing out unmetered air on a maf setup and sucking in unfiltered air. id try putting in both springs and gong full soft or run the hard spring and go full hard then try and adjust
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