Re: [DML] Re: Performace fuel system
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Re: [DML] Re: Performace fuel system

Quick answer: No on both counts. increasing primary pressure increases 
fuelling, but the lambda system will fight you proportionally so until 
you get outside the lambda system's "band of adjustment", it won't do 

Without going into massive detail, pressures in the system are set with 
a spring loaded valve that bleeds fuel back to the tank. By setting the 
pretension on the spring, you set the pressure where the system reaches 
an equilibrium. As the engine requires more fuel, the pressure will 
start to drop, the valve closes a bit, reducing the flow back to the 
tank, the pressure remains stable. The control pressure is fed from the 
primary pressure through its own regulator valve (Control Pressure 
Regulator anyone?), but is ALWAYS lower, so regardless of how you set 
the primary pressure, the control presure will remain constant, unless 
the primary pressure drops below control pressure, which it will only 
ever do if the pump fails, and by the time it does the engine will have 
stalled anyway.

One of the "cheats" on an EFI system to run more fuel on a stock ECU is 
achieved by upping the primary fuel pressure using an adjustable valve. 
Widely available, often with a gauge attached.

I love hydraulics, you can do so much off the back of a few very simple 
principles. Yes, I am currently single...


Marc Levy wrote:

> I have been told by a number of people that INCREASING
> the fuel pressure on these fuel systems will LEAN the
> mixture. Yes, I know it does not make sense.. But
> when it was explained to me, it made sense at the
> time... I forget the reason now!!
> Also, if you increase the pressure, then wont you also
> increase the resistance on the plunger?? if so, you
> will be making it harder to open the the meter flap
> and it will cause additional restriction in the intake
> path.

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