Quote:

Two adjustments are necessary with this regulator. N/A engines that are subsequently fitted with forced induction
often exhibit extreme leanness in the range of 4 inches of vacuum to approximately 3 psi boost. The cause for this
is that the turbo/supercharger can achieve atmospheric pressure in the manifold prior to the throttle being fully open.
Without full opening, the throttle position sensor will not properly inform the ECU of what’s going on, hence, a lean
condition occurs. This is not as prominent in later model OBD2 automobiles where the O2 sensor feedback covers
a broader range.

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The first adjustment of fuel pressure is at the atmospheric pressure point, and can be done best at idle. To simulate
passing through the zero point, the vacuum line must be removed from the 2025. The regulator then sees
atmospheric pressure as a signal, the same as zero on the boost gauge. Control of the fuel pressure at the zero point
is by the On Set Screw in the center of the regulator. Clockwise on the screw will raise the pressure. Once adjusted,
plug the vacuum line back onto the regulator and observe the fuel pressure drop back to the stock figure. A
suggested pressure for starters is 48 to 50 psi. Please understand, this will vary from engine to engine, and is not a
magic number. The “magic” number is whatever pressure your vehicle requires to pass thru the boost onset without
the lean flat spot. It is not unusual to see pressure anywhere from 40 psi to 55 psi. Use whatever works best.

The second adjustment, the needle valve, controls the rate of gain of fuel pressure versus boost pressure. The lowest
rate of gain is with the needle valve fully open, the highest, fully closed. Clockwise closes the needle valve. Figure
2025 offers a typical guide to fuel pressure versus boost pressure. Caution: There is a vague limit that exists with
regard to the maximum possible fuel pressure. The industry Barbara S of injectors jamming at 50 psi and the flow
not increasing with pressure is not correct. It is possible for a very large injector (90 + lbs/hr) to jam at 100+ psi
of fuel pressure. At anything less than that, jamming is not going to happen.