I'm recirculating

 

and how is it, that by only taking out the smaller spring, that cures the problems or low idle/stumbling?

 

I did the single spring mod before I put it in the car
no problems whatsoever

 

holds boost AOK? I'm running 23lbs

 

I just had to chime in here because there is so much misinformation floating around the internet, it's ridiculous.

I've had the type-S for over 3 years now on my Eclipse. The lower nipple goes to a sealed chamber under the valve. The upper nipple goes to a sealed chamber above the valve.

The upper nipple is for a vaccum line, so a vacuum can pull the valve open, such as when you lift off of the throttle creating a vacuum in the intake manifold. The lower nipple can either be vented to allow air to enter/escape as the valve is being pulled up and down, or it can be fed a pressure source pre-thottle body. This will help to avoid surge at part-throttle lift and will also assist in opening the valve quicker.

You shouldn't weld this lower nipple shut or cap it off. It will just make your BOV valve harder to move around and it will eventually cause an internal leak in the membrane separating the chambers.

If anything, leave the lower nipple open. However, I would recommend to hook it to a pressure source pre-thottle body. This is much better than even the single spring mod that is mentioned on the forum. If you want an explanation of what happens when the lower nipple is hooked to a pressure source, read below. If not, you don't have to read anymore.

Say that you are in boost, boosting 20 psi, then you lift off the throttle to shift. The BOV opens by the vacuum going to the top nipple of the BOV. Well, there is still pressure in you IC pipes, so you can also tap a pressure line from your IC pipe to the lower nipple. So now, you have a vacuum pulling the valve from the top and a pressure pushing the valve from the bottom. Your BOV will work much better this way. Also, you can keep the screw on top rather tight and you can use two springs. Without the lower nipple hooked up, you may need to do the single spring mod, but that may hinder the ability of the BOV to hold higher boost levels (mine holds 30+ psi just fine).

Secondly, almost all BOVs are prone to part-throttle lift off 'flutter' or 'surge'. Well, if you hook the bottom nipple to a pre-throttle body pressure source, this will be fixed, too. Say that you are boosting 20 psi again, and you back off to 1/4 throttle. Well, there won't be any vacuum in you intake manifold, so if you only have the top line connected, the BOV won't open. It may partially open or flutter because of the pressure being backed up in the IC pipes. Well, if you have the lowe nipple hooked up, when you lift to 1/4 throttle, the pressure under the valve will be greater than the pressure on the top of the valve (the top nipple), so the valve will be pushed open.

Sorry for the long read already. I'll stop here. But, the type-S is really a good BOV, if you use it correctly.

Also, as a side note, I have found that the thread for the screw on top can be a major boost leak. I used a little thread sealant and mine holds boost perfectly. Before, when it leaked, it would only hold 10 psi (when it was off the car for testing using a hand pump).

Eric