Greddy Type-S Problem. Please Read!!!

[jm1080]

ok so I bought a used type-s on ebay (authentic) and it was in real good condition. Anyways when I put on my hard IC pipes I installed it and I noticed that the threads were gone from the inside of the bov where the screw adjusts.

So I got help from some of the guys in the forums. Paul made new threads on the BOV, and put in a new screw, just a bit bigger so it can fit in the new threads. There are no leaks now or anything when adjusted hard. But you cant hear the whistle that the type-S is known for Anyways I start to loosen it up and u hear a soft whistle on idle like a leak. And when I tighten it it goes away. Does anyone have any idea how I can get the whistle back? Could it be the new screw that we put in?

By the way before it made the really nice whiste. Now if it makes a really bad whistle like 30seconds after it blows off and it sounds like a dying bird.....plus its real soft and it sometimes just whistles slowly on idle when i loosen it up.. Anyone have any idea??

Thanks!

 

[rarson]

You guys are all over the place. Let me try and help you out.

I used to run the Type-S for a while. It would always leak at idle and whistle when releasing boost. This is the only acceptable way I could run the thing (loose).

You can tighten it up, but you'll get BOV chatter. This isn't actually surge (I'm just pointing this out to help with confusion between compressor surge and BOV chatter/flutter/whatever you want to call it). What is happening is that the BOV is adjusted too tight and the spring is slamming the BOV shut. Boost builds back up and it opens again. Process repeats. This isn't compressor surge (look on a site that explains compressor maps to understand what surge is). I wouldn't worry too much about the turbo, because it can take that kind of pressure, but I personally dislike the idea of my IC piping seeing rapid pressure fluctuations.

In my opinion, it's better to have the BOV loose than tight. Why? Because first off, you really have to crank on the thing to get it to not leak at idle (because the top of the diaphragm sees vacuum at idle). If it's not leaking at idle, you probably have it too tight. Secondly, if you're not using the bottom port (leave it open to atmosphere), then you're not placing pressure on the bottom of the diaphragm... this means that the spring pressure doesn't need to be as much to help to seal the valve (since the top of the diaphragm IS seeing boost pressure, sealing the valve). And if it's loose, you can avoid those pressure fluctuations.

The bottom port is NOT for bigger turbos... if anything, it's for smaller turbos because if you use it, you'll have to tighten the BOV to make it hold boost. All it does is send pre-TB boost pressure to the underside of the diaphragm, which helps it open faster. The 1g BOV has the same exact port on it, except it takes pressure off the bottom of the BOV where there is a gap between the two flanges (that's why the gasket has a big open area in it).

What happens when people start running high boost with 1g BOVs? They crush them (which is the wrong thing to do). It helps them hold higher boost, but guess what? They're just #$%@ing around with spring pressure like you guys are doing. The proper way to "fix" a 1g BOV is to block the pressure off and open the port to atmosphere... which is the same exact thing as taking the Greddy and leaving the bottom port open.

The problem is, now you still have to futz around with spring pressure on the Greddy, and as all of you (like I did) can see, it only takes a few turns of the wrench before the threads are stripped. I recommend tapping new threads and use an allen bolt that fits tightly, and just forget about adding the nut on top to keep it in place (ran mine this way for a few years).

And for all that trouble, you can still get a 1g BOV for much cheaper, and it works better, is easier to setup, and you can mod it for basically free to hold as much boost as you want. Oh, and you'll also notice that other cars, like the Skyline, use the exact same valve. That's because it's a really good valve. I'm actually using an RB25 BOV on my car.

By the way, the valve seat on the Greddy is a bit larger than the seat on the 1g valve, which means that the spring has be tighter to hold back more force. This is probably one of the reasons the 1g valve seems to work so much better.