[s-cars] Relayed FP

[David Forgie]

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