[V8] Rons FP Reg hose

[qshipq at aol.com]

 I like this explanation in it's simplicity.  Put another way, fuel pressure (Differential Pressure at the injector) is a constant to the ecu on every audi v8 quattro.  A disconnect of the Manifold Reference signal eliminates the best indicator of engine 'load' and with the line disconnect the ecu is sending signals to the injectors that have nothing to do with the amount of fuel needed.  Every throttle position injector duty cycle will be baseline 'unknown rich' other than WOT.

Scott J



 

-----Original Message-----
From: Professor GT gmail <CavalloGT at gmail.com>
To: v8 at audifans.com <v8 at audifans.com>
Sent: Sun, Sep 5, 2010 10:51 am
Subject: [V8] Rons FP Reg hose


Ron, 



The vac hose should go from manifold vac to the FP Reg.  It serves to maintain 

proper fuel pressure. In a bit more detail, what it really does is maintain the 

correct pressure drop across the injector. You see at WOT there is 0 vacuum, so 

higher fuel pressure is needed behind the injector to maintain the proper 

pressure drop so adequate atomization occurs. When man vac increases as at CT, 

fuel pressure is reduced through the vac signal to the FP Reg, so once again the 

proper pressure drop, hence spray pattern is obtained. This of course is aimed 

at efficiency, max economy and engine/catalytic converter life.



Having the line unhooked gives max fuel pressure across the board and results in 

a wasteful over-rich condition at high vacuum (no-load/idle) conditions which 

can also shorten cat-con life due to excessive heat from the over rich 

condition.

 Unlike some may think this does NOT improve max power one bit, because there is 

0 vac signal to the FP Reg at WOT anyway. 

Hooking up the vac line should improve Driveability, unless of course the line 

was disconnected to cover up some other fuel system shortcoming such as poor 

injector flow.



Hope this helps !



Thanks,



ProfessorGT

(Sent from my iPhone4)

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