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beepbeep beepbeep is offline
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Join Date: Jun 2001
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Originally Posted by Alan L View Post
Thinking about this, Goran, are you sure it would work? I guess you have done it and know it will. But in theory, I would have thought you would have equalised pressure thru whole boost system. For instance, if your gauge reads 0.8 bar, you have same pressure everywhere thru your intake system after the turbo. So, 0.8 bar also arrives at Tee piece on WUR. You bleed a small amount off to loss, but you still have 0.8 bar in the system, so the remaining going into WUR is still at 0.8 bar? If you had a very narrow constriction into the WUR, maybe there is a small delay, but eventually it will still equalise with boost pressure?
Yes, I'm quite sure this works. T-ing a boost signal line has been used forever to raise boost by venting a portion of air going to the wastegate. This is also how usual pneumatic pressure controller works.

It's the ratio between bleed diameter and hose diameter that is determining the pressure loss. If you have a pressure gauge you can try this on your bench. Connect a T-piece to shop compressor regulated down to 0.8 bar and connect pressure gauge to another part of T. Then you can lab with orifice diameter on third nipple of the T until pressure felt by pressure gauge is whatever you would like it to be. I would adjust it to 0.3 bar and then do a test run.


P.S. WUR is working on the same principle. Only difference is that it uses fluid instead of air. WUR "bleeds" certain amount of fuel and thus lowers the control pressure. If you can shape boost pressure entering the WUR, you can also shape the fueling on boost to reasonable degree. You can do it in many ways: by changing the WUR spring force (which you mentioned), by decreasing the control pressure trough Mercedes BTR (which is in place?) or by manipulating the boost signal to WUR (which I suggest).
Thank you for your time,

Last edited by beepbeep; 08-06-2008 at 01:46 AM..
Old 08-06-2008, 01:41 AM
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