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fredmeister fredmeister is offline
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Join Date: Oct 2002
Location: Baltimore, MD, USA
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Originally Posted by 911st View Post
System Pressure I think is the hurdle pressure the fuel pumps have to achiave for the fuel head to be sure it has enough fuel to operate correctly.

Increase this to much and the fuel pumps might not have the ability to support it.

If the fuel pumps can not deliver at a pressure above the system pressure setting, no fuel will blead off out of the valve you have shimed and then go back to the fuel tank.

I could be wrong.
You are right about the differential presssure being controlled within 0.1psi or so by the internal springs in the fuel head and remaining relatively independent of this system pressure value. Theory is that you are controlling flow WITH ONLY ONE VARIABLE THAT BEING ONLY by opening more area in the slits for the fuel to flow thu, eliminating flow changes due to any pressure differential that would arise without the internal springs. The CP does control the amount of travel on the plunger and thus fuel delivery. It is independently controlled of system pressure by the WUR. However, with higher system pressure I think the fuel injectors operate at higher overall pressure and thus flow more fuel. I am not sure but from what I have seen of exploded views of the Fuel head, this is how it seems to work.
1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
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Old 03-10-2009, 02:45 PM
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