90 Quattro 20V (Canada) L5-2309cc 2.3L DOHC (7A) (1989)
Fuel Pressure Regulator: Description and Operation
Intake Manifold And Injector Assembly
The fuel pressure regulator, mounted near the center of the fuel rail, regulates fuel system pressure so that the difference between intake manifold
absolute pressure and fuel system pressure is constant.
Injector Duration Vs. Quantity @ Different Manifold Absolute Pressures
When manifold pressure is low (high vacuum) more fuel will spray from the injectors than will at high manifold pressure (low vacuum) for the same
injection duration and fuel pressure. The fuel pressure regulator increases fuel system pressure as manifold absolute pressure increases so that the percent
change in injection duration equals the percent change in the quantity of fuel injected.