All regulators work by adjusting the fuel pressure of the fuel rail, against the air pressure in the intake manifold.
99% of the time, there is a valve against a spring that accomplishes this. The front side of the valve is the fuel flow. The back side is air, which has a line going to the manifold. The higher the manifold vaccuum (low throttle) the more the valve is open. Lowering the fuel pressure. As the manifold pressure transitions to less vaccuum as throttle is applied, AND will continue to transition into boost (Which is nothing more than higher pressure than the 14.7psi we already live in.) the valve is pushed closed by the spring. The more closed it is, the higher the pressure.
Just like holding your penis too hard when you pee, or putting your thumb on a garden hose.
The adjustable part comes in multiple forms. Adjusting the base pressure, and adjusting the rate at which the fuel pressure changes with manifold pressure.
Most FPR's rise & fall at a 1:1 ratio. This keeps the pressure at a constant level as manifold vaccum & boost change. (A 1:1 ratio will keep you from loosing fuel pressure under boost. If it was less than 1:1 the higher atmosphere pressure in the manifold would make it corrispondingly harder for the fuel to come out.) These regulators will refferance into "boost" until the valve hits the housing & can't travel any farther. This won't give you extra fuel. It simply keeps you from loosing fuel. (to say it again lol)
A 2:1 ratio would mean for every psi change in the manifold, it would change 2psi fuel wise.
Common are 1:1 for N/A applications, 4:1, 8:1, 10:1, 12:1 for forced induction.
Most Toyota systems operate in the 30-50psi range. But provided the injector springs are in good shape, are OK into the 90psi range. Fuel lines, and fuel flow from fuel pumps, on the other hand will not like such very high pressure ranges. Which is why running 8:1+ ratios on relatively stock fuel systems (pump, OEM regulator) under more than a afew psi of boost can be bad. Doesn't take much math to see that 12:1 x 10psi of boost = an extra 120psi of pressure...
The fuel delivery curves for pumps & injectors are inverse of each other. The lower the restriction(low psi) on the pump, the more it can deliver. The higher the pressure against the injector, the more fuel they can squirt. What eventually happens is that a pump that might work enough fuel around 40psi, suddenly can't supply near enough if you try to run 90psi. So you have to watch out for that kind of thing.
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Last edited by Toysrme; 04-06-2007 at 09:17 PM.
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