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, Fri, 10 Oct 2003 23:18:16
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The boost pressure applied to the piston will keep it closed. The pressure balances out the pressure trying to open the valve and the spring pressure adds to that.
The big thing, is that the valve is closed at idle and overrun vacuum levels. So with a hot enging, for higher idle vacs, remove the BOV, VAC line connected, see what resistance there is to open the valve with you finger or thumb.
When boost comes on fast, there is time delay with a long VAC line and that BOV has a large spring chamber. These combine to create a time delay. And it takes a certain amount of flow to compress the air space in the BOV's spring chamber.
I just had a look at my old type S BOV in my parts box. I expect that the piston in your type H will be quite large ?32? mm. If the spring has an interal diameter of 22mm, then a wine cork will fill that space nicely and make the valve open and close faster. I found the length perfect for my TurboXS BPV, which probably shares some design features. Use a good quality cork. Do not use a composition cork as this will swell. Where the cork screw went it, remove any pieces that can be picked free that are not solidly attached. You will need to determine if the cork is too long. The cork will simply float free in there.
When you are on boost, if you let off of the throttle a bit, you definately do not want to dump boost as you are not off throttle and you want to be able to get back on boost without starting from scratch. So you will need to listen for boost dump that is not when you want it. If you detect that, then you can add springs. So static piston force balance is one aspect, and response during some throttle dynamics is another.
And you do not want the vavle open at idle or overrun. So the valve should only be open when there is positive pressure.
When you are building boost, a dynamic condition, the pressure on the piston face might overcome spring force and open the valve if the boost is not getting through the VAC line to the spring chamber fast enough. This is where the cork will help by elimiating much of the air space in the spring chamber. I have contacted TurboXS about this issue before, but they don't seem to think that improving the product's operational speed is important. That is a business decision, not a technical judgement. So corked or not, you might need to add washers to overcome this transient leak when boost builds very fast. If you have a MBC, this would be a real possibility.
I find that a bit if synthetic grease plus some engine oil is a good lubricant for the piston. Cecause the type S and H have exposed ports, the piston sides will get contaminated with dirt and grit. I would remove the vac line and unscrew the top and clean and relubricate when changing the oil. Remove the spring and move the piston with your finger inside. You will be abel to feel how the piston moves and will be able to judge how often this cleaning should be done over time.
I hope this helps you inderstand the issues. The TurboXS instructions only address the closed at vacuum issue as far as shimming goes. Otherwise their instructions are less than helpfull. After time, months?years, the spring may have relaxed, so re-checking that the valve is closed at idle is a good idea.
??? Are you welding in an adapter? Make sure that the BOV is located were you can easily access it.
??? What other mods current and planned?
03 9-5 Aero, 27K, SMBC, TurboXS BPV (corked)
posted by 66.139.12...
, Fri, 10 Oct 2003 23:18:16, Sat, 11 Oct 2003 11:58:53, Sat, 11 Oct 2003 15:29:11
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