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billjam's Avatar
 
Join Date: Aug 2007
Location: Perth, Western Australia
Posts: 2,003
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WUR problem - allows air in/out with no restriction

I have an event looming that I need the car in good shape for so I thought I'd do my annual check of fuel pressures and pump and injector flows because I had noticed a few small changes in the way it was running.
A part of the fuel system check is to pressurise the WUR to 0.5 bar to check that it drops pressure fuel pressure under boost.
This is a modified WUR from Brian Leask that has worked flawlessly for the last couple of years.

When I applied air to the WUR (yes, definitely less than 0.5 bar!), all I could hear was air leaking out from somewhere around the WUR. I was able to blow and suck easily through the WUR boost connection, so I pulled the WUR to find the leak. The air leaks out from the hole through the warm pressure adjusting screw in the bottom. As it says in the pic, air pressure (or vacuum) in the main chamber can only escape down through hole B if cone A isn't closing it off. EDIT - I just rechecked this and there is no way that these two parts can get close enough together for A to block hole B, so should there be something else in this hole?

There was no restriction to blowing or sucking air regardless of whether the WUR was hot or cold, so clearly, the cone A isn't closing off the hole. So what is supposed to stop air from passing throught this bottom hole (used for adjusting warm pressure)?
This could explain why my off-boost AFRs have been a bit higher than usual lately as unmetered air has been entering the engine via the WUR.

I guess my question is - what's the problem here?
What could have changed to have caused this problem? Has a sealing plug dropped out of the bottom hole? Can't find anything lying around.

Everything looks OK in the WUR. The diaphragm is good and the WUR increases fuel pressure within specs as it warms up.


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Bill
1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
Day job ... www.sspowdercoat.com.au
Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911

Last edited by billjam; 11-05-2010 at 09:39 PM..
Old 11-05-2010, 08:42 PM
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A pic of the underside might help.
Air vents freely in and out through the adjusting screw hole in the bottom of WUR.
Should there be a plug here?

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Bill
1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
Day job ... www.sspowdercoat.com.au
Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911
Old 11-05-2010, 10:04 PM
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Join Date: Jan 2008
Location: Weehawken, NJ
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Hi Bill


In the first picture, it looks like you've labelled the vent nipple as the one that is plumbed to the throttle body. In my set up, the boost signal hose is plumbed to the nipple that is coming off of the part you've got in the middle of that photo. The one you labelled as going to throttle body is vented to the airbox in my '79.

Maybe they changed the WUR over the years?
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Current: 1983 911 GT4 Race Car / 1999 Spec Miata / 2000 MB SL500 / 1998 MB E300TD / 1998 BMW R1100RT / 2016 KTM Duke 690
Past: 2009 997 Turbo Cab / 1979 930
Old 11-06-2010, 01:00 AM
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Quote:
Originally Posted by jwasbury View Post
Hi Bill

In the first picture, it looks like you've labelled the vent nipple as the one that is plumbed to the throttle body. In my set up, the boost signal hose is plumbed to the nipple that is coming off of the part you've got in the middle of that photo. The one you labelled as going to throttle body is vented to the airbox in my '79.
Jacob, my son, you are the winner!
I had a bit of a senior moment there today and was using the wrong port for testing the WUR boost enrichment At least I got to see the inside of a WUR!

I figured it out not long after I posted, so I thought I'd let it run to see who picked up my dumb mistake. It's all back together and I'm just back from a nice test drive.
While I was in there, I checked my injector pattern and flow rates - can you believe they all flowed the same volume within 1%.
Love this car

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Bill
1988 Carrera - 3.6 engine (with ITBs, COPs, MS3X) and a whole set of turbo body panels waiting in the attic.
Day job ... www.sspowdercoat.com.au
Memories: '68 912, '72 911T, '80 911SC, '84 911, '85 930, '86 930, '87 911
Old 11-06-2010, 04:14 AM
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