[urq] More Weird UrQ Behavior

[Ben Swann]

If you need pictures or information that I have on this, LMK.  The pictures take up a
lot of bandwidth, so maybe best if I sent you things on disk.
 
If I have time (right) - I'll need to make some time, I can perhaps work up a page on
this.  I had intended to do that just after I did the job, but, well I even forgot about
it since the problem is no more!  Two years now without problem since I did this.   I'll
try to work this up for general public consumption.  In the mean time, if anyone wants
the pictures = 1000's of words then send me a R/W CD/DVD and envelope self-stamped with
your return address.  My address is on my site page:
http://www.gtquattro.com/GTQKITS.html page down.
 
I probably should copyright this, since no one else had come up with this before.  Saw
some similar solutions, drag racers, etc., but the UrQ is particularly hard to do
because of space constraint, etc.  The solution is actually fairly easy to implement if
I were to give you instructions and pictures.
 
You will note that later cars use a larger fuel tank feed - better, but not perfect.
Ultimately you notice all AUDI, VW, and cars in general went first to a transfer - dual
pump system - one pump primes the other, then ultimately to a submerged in tank pump.
Why'd they do that do you suppose?
 
Cheers!
 
Ben

  _____  

From: afinn1 [mailto:afinn1 at gmail.com] 
Sent: Saturday, March 27, 2010 1:52 PM
To: Ben Swann
Subject: Re: [urq] More Weird UrQ Behavior


Wow. Thanks ben. 

Andrew Finney 

On Mar 27, 2010, at 7:56 AM, "Ben Swann" <benswann at verizon.net> wrote:

Andrew, 

I'll lay 95% odds you are starving the pump.  Changing to a bigger badder pump won't fix
the problem.  I had this frustration with my EFI converted '83.

What is happening is the tube coming out of the tank is insufficient to provide adequate
flow to the pump. The fuel delivery on the CIS cars is designed to have a higher
pressure and less flow.  When the pressure is dropped and flow increased for EFI it
basically sucks the fuel faster than the 3/8" bent tube can deliver.  The result is
cavitation at the delivery side of the pump.  The problem gets worse as the car runs for
a while.  I hit on the problem by finding I could clear the problem by reversing
polarity on the pump for a second - this drives the air out of the lines. 

There are a variety of permanent fixes ranging in complexity - pre-pumps to surge tanks,
in-tank pumps, modifying the bottom of the tank for a much larger fitting (welding a gas
tank!) and fuel cells replacing original tank, etc.  Look up surge tank and related and
you will find this is a common problem, particularly with drag racing and EFI converted
cars.

I toyed with this for over a year - drove me nuts.  Many on the list probably remember
my frustration.  Pulled the tank multiple times, cleaned the in tank sock, swapped pumps
out - the nice 044 pumps and more expensive pumps only made the problem worse.  I
actually had better luck with a WALLBRO and the OE pump with smaller inlet worked better
than the later CIS pump made for NF/NG!

The pre-pump filter made things worse, and I removed it which helped some, but the
problem persisted.  I did a lot of research and much trial and error.

I did not want to remove the tank unless I absolutely had to.  So my fix was to
fabricate what I call the "fuel capacitor".  It is simple in concept, but devil in the
details since there is not much room to put something between the pump and the tank -
angles, clearance, kinked lines, etc.  It is a 2" copper  confabulation - kind of a 45
Deg. Angle between two 6" pipes making one angled pipe capped at both ends.  The pipe
just fits in between the pump, mounts, brackets and tank.  I had to cut out the unused
portion of the difflock cable assembly - already removed  and being replaced with
pnuematic actuator.  If you need to maintain the cable system then this will be much
harder to implement. 

There is one large outlet that sits at the lowest point in the pipe.  I should have
added a drain fitting because of the lack of pre-pump filter and probably need to drain
it every now an then - I plan to add one later, possibly with a fuel water seperator
that sits sloghtly lower than the assembly.

I toyed with a variety of fuel feed and return schemes, but simplicity prevailed.  Both
the inlet and return are installed in  the  "fuel capacitor".  I need to review what I
did exactly, but IIRC there is one large fitting at the utmost top of the tank - nearly
jammed into the feed line with a very short line. It was difficult to get it installed
without kinking, but once done, there is little to go wrong.

For the return IIRC it it actually teed into the surge pipe offset at slight angle near
the top of the pipe.  I was not sure if it would work, but makes sense that it does and
in fact adds additional but equalized pressure feed side to not only keep the pump from
cavitating, but also keep the feed line from the tank clear of debris.

In short it works, plain and simple.  The only problem I had was using non fuel grade
line which decided to rupture one day - thank God it was in my driveway and not on the
highway.  So use good hardware and plan it out for a good reliable solution.

If you  or any listers want picture of the assembly, LMK and I will send them.  I plan
to put this on my site, but these things tend to take low priority.

HTH. 

Ben 

[Date: Fri, 26 Mar 2010 12:21:43 -0700 
From: AF <afinn1 at gmail.com> 
Subject: [urq] More Weird UrQ Behavior 
To: urq <urq at audifans.com> 
Message-ID:         <ed47d8be1003261221w2a4c5064v1f7af3a500956166 at mail.gmail.com>  

 
So, at the past 2 track events I've attended with my V8 UrQ I have had a weird issue
with engine cutout at high rpms, usually in 3rd gear, but on the straightaways in 4th
gear. They seem to occur during any throttle position, like cresting a hill, or
accelerating out of a corner, which is somewhat unnerving. There are no fault codes
thrown at all, which makes me think it's a fuel supply issue. Here's the weird thing, I
would say it a fuel pump relay issue, but wouldn't the engine stall (that's what my old
UrQ and Coupe GT would do on the highway), but in this case there's no power until I
depress the clutch after slowing a little and downshifting, then the power is all back.
The engine never stalls and shuts off! I confirmed it's not a rev limiter issue by
redlining with moderate throttle input and no issues occured. It's definitely at higher
RPM though. Does anyone have a thought? I thought about relaying the fuel pump, but
wouldn't the engine simply stall with no fuel supply, or will it simply keep running
with the car in motion and clutch out without shutting down or turning on all the
warning lights on the dash?

Any help is appreciated. Thanks. 

Andrew Finney 
1985 UrQ 4.2L ABZ]