[urq] More Weird UrQ Behavior

[Mike Sylvester]

I have a surging problem when under full acceleration.
I typically don't get boost over 20psi. (RS2'ed 3B)
I thought that maybe it was fuel starvation, but the A/F meter is saying
rich during this time.

Mike

www.urq20v.com

> -------- Original Message --------
> Subject: [urq]  More Weird UrQ Behavior
> From: "Ben Swann" <benswann at verizon.net>
> Date: Sat, March 27, 2010 10:56 am
> To: <afinn1 at gmail.com>
> Cc: urq at audifans.com, 'Quattro List' <quattro at audifans.com>
> 
> 
> 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>
> Content-Type: text/plain; charset=ISO-8859-1
> 
> 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]
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