From Bell Engineering:
http://www.bellengineering.net/Pages/products_MRFPR_Instruction.htmlAdjusting the 2035
Three adjustment are necessary with this regulator. NA 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/sc can achieve atmospheric pressure in the manifold prior to the throttle being fully open. Without full opening, the throttle position sensor will not send the proper signal to the ECU, hence, a lean condition occurs. To counter this weÆve made the ôonsetö of fuel pressure rise adjustable. The 2035 can actually start raising the fuel pressure prior to being under boost. This is accomplished by the center screw in the R/R section of the regulator. The actual rate of gain of the fuel pressure rise relative to the boost is under the control of the needle valve at the side of the R/R section. Adjusting the static fuel pressure for normally aspirated operation is the responsibility of the screw at the end of the 1/1 section. In all installations, we urge tuning be aided with an air/fuel ratio meter.
After the regulator is in place, all signal lines attached and the check valve in position, adjustment can begin.
The vacuum control of 1/1 regulation has been set by BEGI to 36 psi at atmospheric pressure (zero manifold). The engine should start and idle properly. Start the engine and inspect for fuel leaks. Correct any leaks before proceeding further.
First adjustment:
Check the idle fuel pressure. It will be less than 36 psi due to the manifold vacuum of idle RPM. Verify the 36 psi setting by pulling the signal line from the 1/1 side of the regulator. It is necessary to pinch or plug shut the removed signal line to read the fuel pressure, as the vac leak will upset the R/R part of the regulator. If the gauge reading is not 36 psi, trim it to 36 with the 1/1 screw. Then snug the jam nut and replace the vac signal line.
Second adjustment:
The second adjustment of fuel pressure is the onset of gain. This represents the fuel pressure as the manifold conditions cross from vac into boost. This is done at idle. To simulate passing through the zero point, the vacuum line must be removed from the R/R side. 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 Allen screw in the center of the R/R side 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 starting point pressure 48 to 50 psi. Please understand, this will vary from engine to engine, and is not a magic number. The ômagicö 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.
Third adjustment:
Adjust the R/R needle valve when testing under boost.
The maximum fuel pressure is controlled by the needle valve and must be determined while driving the car under boost. Start with the needle valve closed, which is fully clockwise.
Pressure calculation:
The fuel pressure required increases with the square of the boost pressure ratio:
Example: 6 psi boost is a pressure ratio of 1.41. With stock fuel pressure of 36 at zero boost, than:
Needed fuel pressure = ( PR2 x 36) + boost = (1.412 x 36) + 6 = 77.5 psi
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 (BS) 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.
