AFPR

How to Add an AFPR

Background
1. The stock Fuel Pressure Regulator (FPR) is typically fixed at 43.5psi.
2. Stock 22lb/hr fuel injectors are rated at this pressure and 100% flow.
3. Fuel injectors cannot operate efficiently above about 80% duty cycle.
4. Injector flow rate delends on fuel pressure.
5. In Closed Loop mode the ECM maintains stochiometric air/fuel ratio by adjusting
fuel injector pulse width.
4. The Block Learn Mode (BLM) cells store air/fuel ratio adjustment data.
5. When air/fuel ratio is tuned the BLM cell values will be 128 +/- 6.
6. An Adjustable Fuel Pressure Regulator (AFPR) is used to adjust the fuel pressure
so that the air/fuel ratio is tuned.

Preparation
1. Remove the cap from the Schraeder valve and wrap a towl around it.
2. Attach a fuel pressure gauge to the Schraeder valve on the fuel rail.
3. Start the engine and let it come to warm idle.
4. Remove the vacuum line from the FPR and plug the hose.
5. Measure and record the stock fuel pressure reading.
6. Turn off the engine, warp a towl around the Schraeder valve and bleed off the
fuel pressure.

Install The FPR
1.   Disconnect the visible vacuum lines from the plenum.
2.   Remove the runner torx bolts from the plenum.
3.   Tap on the plenum with a piece of wood, if necessary, to loosen it.
4.   Lift the plenum slightly and set it aside enough to access the FPR Torx bolts.
5.   With a special Torx bit remove the security Torx bolts around the FPR.
6.   Note the vacuum prong orientation and lift the FPR cap from the base,
      using care not to tear the rubber diaphram.
7.   Clean up any spilled gasoline and the base gasket surface.
8.   Back the AFPR screw out till it is flush with the inside of the AFPR cap.
9.   Place the disk inside the AFPR cap and the diaphram over it.
10. Insert the Torx bolts through the AFPR cap and the diaphram holes.
11. Carefully invert the AFPR cap assembly and place on the FPR base.
12. Properly orient the AFPR cap and run the Torx bolts down snugly.
13. Evenly tighten all Torx bolts, using care to not overtighten them.
14. Tighten the adjuster bolt down one turn CW.
15. Reinstall the plenum and all vacuum lines.
16. Tighten the fuel pressure gauge, start the engine and check for fuel leaks.

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