[urq] WUR findings

[Ben Swann]

Gary,

Without remembering exact  specifics on this, I'll give you enough info. to support
advice to leave the hose routing as indicated in the stock layout.

Basically the WUR has two port on it - one provide pressure to the side of the diaphragm
that enriches and the other to the side that enleans.  Once the temp valve opens, the
circuit allows to enrich and enlean based on manifold pressure.  It seems
counterintuitive at first that both sides of the WUR are plumbed into the same pressure
- wouldn't that cancel out any effect of pressure you likely wondered.  Me too, so I did
some experimenting and somewhere I have notes on the results.

What actually happens is the amount of force on the diaphragm is disproportional.  As I
recall, the port has greater effect on riching up the mixture than is does to lean, but
that is the part I forget exactly and it may be backward.  

I played with this thinking I could get more enrichment by separating out the two and
using other pressure sources - one of them was the venturi effect off the throttle and
there is one off the turbo hose too, as well as some valves and manifold source, and use
of an air fuel meter.  These all met with various and interesting results, but mostly my
conclusion in the end was to fix what is broke with the stock system and leave the WUR
plumbing as it was.  With that you could use the WUR to provide enrichment for greater
fuel at boost, but it is very hard to control with simple valves.

The best way to add fuel if you are upping the boost is some sort of EFI - a
supplementary injector does fine for modest power levels under 300 HP and full EFI like
what I did using Megasquirt to dial in as much boost and fuel as you can safely with
your turbo and other setup.  You can also shim the air flow meter, but that IMO is a
temporary workaround.

I like CIS, but I like EFI better.

Ben

[Date: Thu, 26 Mar 2009 08:45:41 -0700 (PDT)
From: Gary Brown <gmbchef at sbcglobal.net>
Subject: [urq] WUR findings
To: urq at audifans.com
Message-ID: <84785.75341.qm at web82101.mail.mud.yahoo.com>
Content-Type: text/plain; charset=us-ascii

A few weeks ago I was having leaning condition under high boost. Everything was working
as they should, and found that the wastegate actuation stud was stripped, causing the
diaphragm to lift, letting the boost spike. Fixed that, same problem. So...after lots of
urq list archiving and remembering some of the Bosch book topics, I remembered that the
WUP on this car was set up for cold running as well as boost enrichment, but the hose
set up made no sense to me. I have tinkered with that before, but never quite figured it
out. This time, I took an old WUP (CPR) apart, and applied pressure to both nipples then
vacuum to both nipples. What I found was that the two nipples are placed in such a way
that the diaphragm moves the same direction under boost as well as vaccum, the large one
being the boost enrichment. What didn't make sense is the on-off switch below #5
cylinder plug, with the two nipples on it. It has one hose from the manifold going to
it, and
 one hose that is teed off to go to both the large and small nipples on the WCUPR. When
the motor gets warm, the switch closes, and therefore no vacuum or pressure goes to the
CWPUR. This is as per the underhood and IST docs. So....I by passed the switch all
together...guess what....enrichment under high boost! But, now enrichment under decel
too. When I re-install the vacuum hose from the manifold to the switch and the switch to
the small nipple, that will take care of that. But, it does sound cool with that rolling
burble under in-gear decel! I'm sure that this has been written up somewhere, but I
couldn't find it. 

HTH

Gary ]