[s-cars] Relayed FP

[Scott Justusson]

My concern with inline fuses are the common associated, nothing to do with the actual fuse, but it's installed environment... The ATC inline fuse holders vary in quality, their mounting should be mechanical (not dangling inline with the wire) to eliminate vibration, and they trap heat that can reduce the overall rating/life of the fuse.  I'm not a fan of 99 cent electrical protection of a critical electrical component counting on 100% duty cycle.  Hella makes a single 'open'-rigid mounted ATC inline fuse holder (Hella PN:  87134) that would be a 'minimum' for this FPR mod IMO.  On all FPR relays I like to use a minimum 2 gang aux fuse block, and I also like to use a rigid mounted relay holder (so the relay can be replaced easily).   The four gang block I commonly use is Hella 62935 mounted under the back seat.  The rigid mount Relay Holder is Hella PN: 87123 and comes with the proper stress relieved terminals that Audi uses (2 crimps - one on wire jacket and one on wire)
 
A good source for individual Hella components is www.rallylights.com

Cheers and HTH

Scott J
92 v8 ABT Chipped
95 C4 Avant FWD
2 x urq
2 x CGT

 

-----Original Message-----
From: David Forgie <forgied at shaw.ca>
To: Scott Justusson <qshipq at aol.com>
Cc: s-car-list <s-car-list at audifans.com>
Sent: Mon, Nov 14, 2011 12:48 pm
Subject: Re: [s-cars] Relayed FP


Scott: Thanks, I appreciate your comments about use of the larger gauge wire.  I was going to do that
but at the time, I couldn't find wire with insulation that wouldn't get eaten by the gasoline.  I did eventually
get some teflon-coated wire but I have yet to install it.
 
One comment that I have to argue is the use of a spade-type inline fuse.  That is exactly the same fuse
 type as the OE fuses in the fuse panel.  I have not had any fuse failures in 13+ years of UrS ownership so
 I am  not concerned about that fuse failing (hasn't in 7+ years so far).  I presume that you have different 
experiences with these fuses.
 
Dave F.

----- Original Message -----
From: Scott Justusson <qshipq at aol.com>
Date: Monday, November 14, 2011 10:21 am
Subject: Re: [s-cars] Relayed FP
To: forgied at shaw.ca, s-car-list at audifans.com

> 
>  Good information, but also know that there are several
> 300+ATWHP cars running no relay mod, hence my suggestion it may
> not 'solve' anything.  To your writeup itself, when I did 
> one of these mods to a 400ATWHP S car, I also replaced the stock 
> 14guage wire to the actual pump in the tank, with 10 guage wire 
> from the aux relay pin 87 feed, and added a redundant ground of 
> 10guage wire to the pump as well.  Likely massive overkill, 
> but I also do this routinely on the urq external pumps.  
> Also, I don't use a crappy failure-prone 'inline' fuse for this 
> mod, I usually mount a aux fuse block under the rear seat, which 
> also gives a couple slots to add 12v feed to the headlights, 
> which can also suffer light output from lower than battery voltage.
> 
> Cheers and HTH
> 
> Scott J
> Relay mods aplenty
> 
> 
> 
>  
> 
>  
> 
> -----Original Message-----
> From: David Forgie <forgied at shaw.ca>
> To: s-car-list <s-car-list at audifans.com>
> Cc: qshipq <qshipq at aol.com>
> Sent: Thu, Nov 10, 2011 8:52 pm
> Subject: [s-cars] Relayed FP
> 
> 
> Scott:  As detailed in the link to one of my DIYs that JaMu 
> provided(http://forums.quattroworld.com/s4s6/msgs/24327.phtml) 
> there was a significant improvement in the
> voltage at the fuel pump when the OE fuel pump relay was simply 
> used to trigger another relay sitting
>  beside the battery and 4 ft from the fuel pump instead of 
> allowing current to flow forward from the
>  battery, through the fuel pump relay and all the way back 
> to the fuel pump.  This was done to help
>  eliminate significant pinging on certain unnamed (okay, 
> Pastore) "RS2" software that Sean D. and I were
>  experiencing on Chevron 94 shortly after we RS2's our AANs 
> back in 2004.  The new relay definitely
>  helped to decrease the occurence and severity of the 
> pinging.  The real solution for us was better
>  software  (MRC Stage 3 in my case and Dahlback MTM in 
> Sean D's case). 
>  
> It must have been a good idea if 034 commercialized it.  ;>)
>  
> Dave F.
>  
> Scott J expounded:
>  
>  >The urq pump is also relayed from the factory, and this 
> is a standard issue mod, not based on theory,
>  >it's a known practical application of voltage at the pump 
> vs pump output.  The main reason to do this
>  >relay mod is 17 feet of wiring between the factory FPR 
> and the fuel pump can create quite a voltage
>  >drop.  Easy to test this improvement, if battery 
> voltage = voltage at the fuel pump = no improvement. 
>  >IME with Audis, rarely does the battery voltage = voltage 
> at the fuel pump.  And the difference in fuel 
> >pump output is quite significant when voltage drops:
> >http://performancefuelsystems.com/images/clip_image004_001.jpg
> >
> >I won't go so far as to say it will *solve* anything, but low 
> voltage at the fuel pump can create running
>  >problems under boost.  The good news is with many 
> Audi batteries mounted under the seat, this is a
>  >simple and effective mod.
> >
> >HTH and my .02
> >
> >Scott J
> >Relayed fuel pumps aplenty
> 
>  
>