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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,289
I'll add that the reason the frequency valve can vary the amount of fuel pressure in the lower chambers up and down in relation to system pressure by returning some of that fuel to the gas tank is because the fuel feeding the lower chambers has to flow through tiny orifices leading to them from fuel that is at steady high system pressure.
Anotherwords the frequency valve that is just an inline electronic fuel injector can bleed off some of that fuel in the lower chambers and return it to the gas tank faster than it can flow through the small orifice from system pressure to replenish it.

That is the same reason the control pressure/warm up regulator everyone calls a WUR here can change hydraulic fuel control pressure pushing down on the control plunger in the middle of the fuel head while the air flow meter linkage is trying to push it up from the bottom.
The fuel feeding the control pressure chamber above the control plunger has to flow from system pressure through a tiny orifice so the CPR can easily vary that hydraulic control pressure up or down by returning some of it to the gas tank.

This is why you need two big fuel pumps to feed 930 CIS.
This crazy mechanical fuel injection system has to return fuel being used as hydraulic control pressure to the tank for it to flow and inject more fuel to the constantly flowing injectors at high fuel pressure into an intake manifold running around 15 psi higher than atmospheric pressure.

The euro fuel heads only have one hydraulic control pressure circuit returning fuel to the tank and the aluminum lambda fuel heads have two seperate hydraulic control pressure circuits returning fuel to the tank.
That is why the lambda heads run at higher system pressure than the euro heads.

Because the lambda heads have the more flexible synthetic diaphram between the upper and lower chambers they are capable of flowing alot more fuel than the euro heads after they are modified and adjusted.
They also weigh alot less and don't rust inside like the euro heads. When modified they are much better if you are after more fuel.
Old 04-18-2013, 07:23 PM
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