[urq] WUR findings - Warmup Pressure Regulator

[Ben Swann]

I just sent a reply to Cody, so read that for a little more info.  It is helpful to read
the Bentley to gain some details on the various CIS and CIS-E systems.  To really get
the whole story, BOSCH Fuel Injection by Probst is the required bedtime reading.

WUR - Warmup Regulator

WUP - something one used to get when they were naughty.  I think was a typo, but could
perhaps mean Warmup Pressure

WCUPR - A little harder to type, but actully more accurate meaning Warmup Control
Pressure Regulator and should probably be WUCPR or just CPR which might get confused
with something that is done then a heart stops beating.

CWPUR - probably another variation on the above.

Most folks call it the WUR or CPR.  In short this device has been used on CIS based cars
since the 70's or before when Bosch fuel injection came about.  It regulates the control
pressure that acts as a counterforce in the fuel metering head.  By controlling this
pressure as the car warms up and also for load related condition (manifold preesure) the
fuel mixtrue can be enriched for cold starting or heavy load, or enleaned as the engine
warms up or is cruising.  The devil is in the details.

Ben

-----Original Message-----
From: Bares, Vittorio [mailto:Vittorio.Bares at nuance.com] 
Sent: Thursday, March 26, 2009 3:46 PM
To: Ben Swann; gmbchef at sbcglobal.net
Cc: quattro at audifans.com
Subject: RE: [urq] WUR findings

I feel dumb...what is:
-- WUR
-- WUP
-- WCUPR
-- CWPUR

Unless they are the sounds of my car makes when its not working right ;)

Vittorio -

-----Original Message-----
From: quattro-bounces at audifans.com [mailto:quattro-bounces at audifans.com]
On Behalf Of Ben Swann
Sent: Thursday, March 26, 2009 3:36 PM
To: gmbchef at sbcglobal.net
Cc: quattro at audifans.com
Subject: [urq] WUR findings

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 ]
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