Greddy type S lower nipple?

dac69er

dac69er

Super Moderator
is there anyone on here actually using it?

i was thinking that its obviously there for a reason but the info ive found online seems a bit flawed.

just wondered if anyone had any definite answers as to where to plumb it in? something like the original instruction manual diagram would be good!
 
D

Dave@TM-developments.com

Trader
Q: How does the Greddy valve work?

A: The Greddy valve has a rubber diaphragm, steel valve and vacuum assisted movement. The boost valve that is normally closed is held shut via spring tension at the top of the valve. A rubber ring at the bottom of the valve flange helps prevent boost leakage. A screw/nut at the top of the bov adjusts the tension of the spring and thus the sealing power of the valve. Normally under boost, the boost pressure on the top nipple helps keep the valve shut along with spring tension against the boost that is underneath the valve. When the throttle plate is closed, your manifold now has vacuum in it while the intercooler pipes are still pressurized. The vacuum, when transmitted to the BOV, helps assist in bringing the valve up, while the escaping boost pressure pushes further to fight its way out. The higher the vacuum level and the higher the boost, the more the valve will move up. Once the boost is evacuated, the spring tension will push the valve shut.



Q: What is the 2nd bottom port for?

A: The 2nd port can be used to help lift up the diaphragm under low vacuum conditions. If you are experiencing surge before your pressure release, hook up the 2nd port to your turbo pressure line. The vaccum at the top of the diaphragm and the boost pressure under the diaphragm will help it open faster. Keep in mind that the valve will not stay open as long using this method, so the sound will not be as loud.



Q: How do you adjust the Greddy BOV?

A: The BOV has an adjusting screw on the top. Use a 10MM wrench to loosen the nut that keeps the screw in place. Then use a 3MM allen key to turn the screw back and forth. Tighten the 10MM nut (snug but not too tight) when you are finished. First, do a rev test with the BOV if you will vent to air. After a few aggressive revs, the valve should close quickly on it's own power. If it does not close or takes too long, then the valve is set too softly. Then do a test drive to listen and be sure that you are getting proper pressure release. If you boost highly, you may want to consider a Type R Greddy instead.
 
dac69er

dac69er

Super Moderator
ive read stuff like that dave, but the problem i have with that is that you will essentially create a boost leak by doing that as the main shaft is not an airtight seal???
 
dac69er

dac69er

Super Moderator
Dave@TM-developments.com said:
Try it and see Duncan. Its a bit like having two on a wastegate. Creates a push pull effect that responds quicker
Click to expand...

hmmm, suppose i could give it a go :confused:

does the bottom port leak through where the shaft is if you blow through it? that must be even harder to make an airtight seal due to the heat?
 
R

RGM1800

Member +
dac69er said:
hmmm, suppose i could give it a go :confused:

does the bottom port leak through where the shaft is if you blow through it? that must be even harder to make an airtight seal due to the heat?
Click to expand...
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where do you intend to plumb it mate? im also using greddy type s. i leaved the lower nipple as it cos i dont have definite answer on what does it do and where to plumb it. maybe you can shed a light on it
 
dac69er

dac69er

Super Moderator
basically you pipe the lower nipple to the hot pipe somewhere coming off the turbo, some even say to T into the pipe that leads to your actuator. just sounds like crap as if you blow through the bottom nipple air will leak past the shaft.

at 1 bar or so boost you will be bleeding off air that should be going to the actuator and essentially raise the boost.
even if you make a seperate run to the lower nipple from the hot pipe you will still be leaking boost through the shaft of the bov at all times
 
R

RGM1800

Member +
dac69er said:
basically you pipe the lower nipple to the hot pipe somewhere coming off the turbo, some even say to T into the pipe that leads to your actuator. just sounds like crap as if you blow through the bottom nipple air will leak past the shaft.

at 1 bar or so boost you will be bleeding off air that should be going to the actuator and essentially raise the boost.
even if you make a seperate run to the lower nipple from the hot pipe you will still be leaking boost through the shaft of the bov at all times
Click to expand...

so its prone to boost creep? i think using the lower makes your bov does both job of bov and a wastegate?
 
dac69er

dac69er

Super Moderator
i havnt done it, but it will just increase the boost the same way that a bleed valve would as its bleeding off pressure before it reaches the actuator, nothing to do with boost creep.
if you take your boost source from the pipework and fit it to the bov lower nipple you will just have a constant boost leak.

it wont make the bov act as a wastegate, its not on the exhasut side of things. if you connected it to the bottom nipple only it would work as a crude pop off valve, but due to the constant leak by on the shaft it wouldnt be the most accurate.
 
C

Corey_gt

Admin
The main shaft should be a good seal mate I dont know where your thinking its going to leak from it does'nt leak when I blow through mine. Tbh I think your looking into it too much the nipple is basically there to let air out from when the diaphragm is moving if it was'nt there the bov would'nt work. When its connecting up to a vac line to it there is a sucking effect on the diaphragm helping it to open a small bit faster but you would'nt notice it. I just leave mine venting to the atmosphere as it sounds rubbish when the lower nipple is connected up.
 
dac69er

dac69er

Super Moderator
its a brass bush so its not an airtight seal, it will never seal 1 bar boost.

all im asking is that people are saying this is how it should be connected up, with a boost source before the tb connected to it. but i cant see that being a good idea due to the leaking.

its been venting to atmosphere since ive had it, but was just interested in the "correct" way to pipe it up.
 
Djaniero

Djaniero

Member +
Hi dac69er,

Did you ever connect the low nipple in the end? Thinking about buying one for my GT, but read mixed reviews on whether or not to connect the lower nipple?

Thanks
 
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