WUR/CPR was Re: [urq] Parts recommendations

[rob hod]

     Thats a good description of the WUR. The point being that the WUR , by
lowering control pressure can have a very significant effect on mixture
richening. Non lambda cars rely on this for cold enrichment.

       Somewhere in thread someone asked what a thrmo-pneumatic valve is.
IME with Audi's this means simply a valve bolted to a part of the engine
that gets warm, and that opens (or shuts) at a certain temperature. To
illustrate,  one example is common to both of my non-cat non-lambda euro
spec Audi's. - there is a system by which acceleration enrichment is given
by a short burst on the cold start Injector. This is accomplished by an
electrical vacuum switch connected to a inlet vacuum line. This vacuum line
goes Inlet -> Thermo-pneumatic Switch -> vacuum switch. Now don't ask
whether the thermo switch is open when hot or cold 'cos its never caused a
problem, so I don't know, but I know it's there to disable the system in one
of those states (I would guess once the engine is warm).

        So as a corollary I can imagine a situation where control pressure
may need to be moderated by vacuum, but only perhaps when the engine is
colder, hence the use of a thermo-pneumatic valve to disable this part of
the system when warm.

    Hope you can all follow what I'm tryin to say, I'm not sure I can!!

        Cheers Rob.

> Message: 7
> Date: Wed, 30 Mar 2005 12:04:28 -0700
> From: Charles Baer <charlie at istari.com>
> Subject: Re: WUR/CPR was Re: [urq] Parts recommendations
> To: Ben Swann <benswann at comcast.net>
> Cc: James Howard <spam.me1 at ntlworld.com>, urq at audifans.com, Ingo
> Rautenberg <i.rautenberg at waratap.com>, quattro at audifans.com
> Message-ID: <424AF83C.1060603 at istari.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> I found what sounds like the explanation in a page from my 911 bookmarks
> (in the part about lambda sensors):
>
> "Drops control pressure when engine is cold, resulting in a richer
> mixture during
>   warm up. . The term warm-up regulator is a bit of a misnomer in that
this
>   component actually regulates control pressure the entire time the
> engine is running.
>   It changes the pressure during the warm-up period. Power is applied to
> bimetal
>   strip in the regulator when fuel pump is on. As the internal resistor
> heats up the
>   strip, the control pressure supplied to the fuel distributor
> increases, leaning the fuel
>   mixture. On cars with vacuum control, the WUR enriches mixture under
load
>   determined by lower intake manifold vacuum. Some versions also modify
> pressure
>   with altitude. Lambda sensor systems don't use the vacuum chamber
> because of
>   this adjustment being automatically accomplished by the lambda system
> electronics
>   box. '81 saw a change in the internal resistor configuration for the
> WUR. A second
>   resistor was added to heat the bimetallic spring, controlled by a
> bimetallic switch.
>   This allows the mixture to lean out more quickly after start-up,about
> 2 minutes
>   compared to the former 3 minutes."
>
> Many 911s and 930s use both lines, I've heard some SC guys say they've
> used 5000 parts
> and passed emissions so there is some compatibility to be found between
> Audi/Porsche
> specs.
>
> This page is 911 oriented, but may give some more insights:
> http://members.rennlist.com/jimwms/CIS/CIShome.html
>
> Charlie
>
> Ben Swann wrote:
>
> >Hey - I was looking a Huw's diagram.  This makes more sense, but I don't
get
> >it yet.
> >
> >See: http://www.humanspeakers.com/audi/vacuum-system.htm
> >
> >Knowing what each CPR port does would clarify - quattro list in copy in
case
> >anyone knows there - Huw?
> >
> >This includes a valve  between the larger of the two CPR lines and the
tee
> >and another line directly to manifold.
> >
> >Hmmm - wonder what is going on here.  One must be for vacuum and the
other
> >for positive pressure, or ???
> >
> >Ben
> >----- Original Message -----
> >From: "Ben Swann" <benswann at comcast.net>
> >To: "Ingo Rautenberg" <i.rautenberg at waratap.com>; "James Howard"
> ><spam.me1 at ntlworld.com>
> >Cc: <urq at audifans.com>
> >Sent: Wednesday, March 30, 2005 12:45 PM
> >Subject: Re: WUR/CPR was Re: [urq] Parts recommendations
> >[Ingo describes what I was talking about , and it just didn't make sense
to
> >me.  To simplify - on my '83(as per diagram under hood)  a line comes off
> >the thermo time valve/switch and tees off to the 2(two) ports on the
CPR -
> >if the valve is open, then you get manifold pressure, if it is closed
then
> >does nothing.  Perhaps some re-teeing or one way valving can be applied
to
> >make this work better.  My engine seems to be running lean on startup and
at
> >boost, and I beleive it is the CPR - yes fuel pressure test is in order.
> >Was hoping to try a WUR/CPR from an '83 CGT NA (not turbo) as they look
> >identical, but have not checked the numbers.  Anyone know offhand?
> >
> >My setup is not like: http://homepage.ntlworld.com/jh.666/diag.jpg but
like
> >Ingo says - what do the two different ports do specifically - thought one
> >actually facilitated enrichment under boost.
> >
> >I thought this WUR could be used to facilitate higher fuel pressure at
boost
> >by lowering control pressure, but from what jim says is not the case.
Also
> >if the thermo time swith closes rather than opens as the engine warms,
then
> >the tee'd off lines do nothing once the engine is warm - so this could
> >probably be improved upon.
> >
> >Uh what is thermo-pneumatic valve?  Maybe it is supposed to work somewhat
> >with pressure too and not just a temp switch.  Why two ports then?  Does
one
> >work under vacuum and one under boost - which is kind of what I thought.
> >
> >