AEM 25-302BK Universal Adjustable Fuel Pressure Regualtor User Manual
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This part is legal in California for racing vehicles ONLY and should NEVER be used on public highways.
Congratulations! You have just purchased the finest adjustable fuel pressure regulator for
your car at any price!
AEM billet aluminum adjustable pressure regulator.
The AEM universal adjustable regulator bolts directly to any high volume fuel rail. It is CNC
machined from 6061 T-6 aluminum. The fuel outlet and inlet ports are tapped to 9/16-18 thread,
which allows the use of several different hoses. The vacuum reference is 1:1 ratio so for every
pound of boost on a turbocharged or supercharged application yields a 1-pound rise in fuel
pressure. The range of adjustability is from 20 PSI to the maximum the fuel pump can deliver.
A unique feature of the AEM adjustable pressure regulator is that the discharge port in the
regulator is changeable. This allows the user to tailor the regulator return volume to match their
fuel pump. A common problem that occurs when using a fixed orifice in a “universal” regulator is
that the fuel pressure cannot be effectively controlled when the fuel pump volume is significantly
higher than stock. In the case of too small of a discharge orifice, there is a large pressure spike
associated with rapid deceleration because the orifice cannot flow enough fuel when the
diaphragm is fully deflected to the open position. This causes a momentary rich condition, which
may lead to a rough idle quality until the pressure stabilizes. Conversely if the discharge orifice
is too large the adjustment is difficult because the response of the fuel flow out of the orifice is
too rapid which makes the adjustment screw too sensitive. The AEM regulator is packaged with
three orifice sizes, .100”, .150” and .200”. They are easily changed by removing the diaphragm
and simply unscrewing the orifice and replacing it with the desired size orifice. The size range
provided with the kit is enough to cover any pump from a stock Honda pump to the largest after-
market pump available. The replaceable orifices are color coded for easy identification.
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