AEM 30-6905 Universal Programmable EMS-4 - Manual (Page 139)

Page 139 of 279 EMS-4 Install and Tuning Guide_Rev 1.6
Fuel Pressure Regulator and Pulse Dampener
The fuel pressure regulator maintains a constant pressure across the fuel injector. The inlet
manifold pressure varies with throttle angle, and engine speed. Small throttle angles and high
engine speed produce low manifold pressure (high vacuum). While high throttle angles and low
rpm give high manifold pressure. In addition to these conditions, low manifold pressure is
associated with idle and high manifold pressure is at full throttle. It is the fuel pressure
regulators job to keep a constant fuel pressure across the injector(s) regardless of manifold
pressure.
Currently, there are several types of fuel pressure regulators in use. Many late model cars use
a return-less system where the fuel pressure regulator is mounted in the fuel tank adjacent to
the fuel pump (and therefore requires no return line back to the fuel tank). In most naturally
aspirated applications these types of systems are adequate. With forced induction or heavily
modified engines, an adjustable fuel pressure regulator with manifold vacuum reference must
be fitted.