Fuelab 55501 User Manual
Model Number 55501-c
Fuel Pressure Regulator
Operating and Installation Instructions
CCAAUUTTIIOONN!!
This product is to be installed only by persons knowledgeable in the repair and modification of vehicle fuel systems
and general vehicle systems modification. Only a qualified technician or mechanic who is aware of applicable
safety procedures should perform the installation of this product.
GASOLINE AND OTHER FUELS ARE FLAMMABLE AND CAN BE EXPLOSIVE!
Perform the installation in a well ventilated location only to minimize the build up of fuel vapors. NO open flames,
smoking or other sources of ignition are to be present duri ng installation, to prevent fire or explosion that can cause
serious injury or death. Grinding, cutting, and drilling must be performed with care to prevent ignition. Draining and
removal of all fuel and ventilation of vapors in vehicle and fuel system is recommended wh en performing such
procedures. Proper eye and personal protection is required at all times during installation.
WWAARRNNIINNGG!!
The Vehicle’s fuel system may be under pressure! Do not loosen any f uel connections until relieving all fuel system
pressure. Consult an applicable service manual for instructions to relieve fuel system pressure safely.
This product is intended for racing, off-road, or marine use only. This fuel system component is capable of altering
engine tuning and therefore not legal for sale or use on emission controll ed motor vehicles.
Product Contents:
Check the diagram and list of components
(right) to ensure that no components are
missing from box. Contact your Fuelab
distributor immediately for replacement.
55501-c Features and Performance Ratings:
Inlet Port Size -8AN Military Port
Outlet Port Sizes -8AN Military Port
Regulation Slope 0.8 PSI/GPM
Maximum Flow
Capacity
Pressure
Adjustment Range
160 GPH with 20 PSI Inlet
(600 LPH at 1.4 Bar Inlet)
Pressure Range “C”
4-12 PSID
(.3 – .8 Bar)
(3X) -908
O-rings
Jam Nut
Plug
(3X) Bracket Lock Washers
Flat Washer
Port Filter
(3X) Bracket
Screws
RegulatorAdjustment Screw
Bracket
Part of Regulator.
DO NOT LOOSEN
WARNING! Exceeding maximum inlet pressure (45 PSI) may result in an over-pressure operating condition.
Before Installation, Plan Entire Fuel System:
These instructions are limited to general topics of regulator component i nstallation and may not include specific
information pertaining to your application. These instructions are written assuming the use of an internally relieved
electric fuel pump with 45 PSIG maximum outlet pressure. Some high pressure pumps may be used with regulator,
but will require a bypass or relief, plumbed prior to inlet of regulator. This regulator has an internal spring that can
be changed for other pressure ranges, including “L” range, for 1-3 PSID and “T” range for 10-25 PSID, if required by
the specific application. Visit our company website for specific details pertaining to example fuel systems and other
solution ideas. Additional information including advanced troubleshooting, any speci al alerts and FAQ’ s pertaini ng
to this and other products is also available.
General Regulator Performance Notes:
The notation “PSIG” means pressure in Pounds per Square Inch (PSI) relative to the prevailing atmospheric
condition or outside air. This is referred to as Gauge P ressure. The not ation “PSID” means pressure in PSI relative
to another pressure source or called the Differential Pressure (rel ative to Pressure Reference Port in case of
pressure ratings). This regulator acts via restriction to control pressure (restricting fuel between inlet and outlet
ports). Only “blow-through” boosted applications for carbureted systems should have a line plumbed to the
pressure reference port. “Blow-through” applications will have limitations based on inlet fuel pressure and boost
pressure. The amount of pressure difference to expect with application of full throttle compared to idle (for naturally
aspirated engines) is a function of how much flow the engine is using (reference Regulation Slope, above for
calculations).
105020521-1, Rev A Sheet 1 of 4
Plumbing Planning Notes:
Minimize plumbing restrictions between carburetor(s) and regulator for peak performan ce. Use –6 AN (3/8”) to
–10AN (5/8”) line as required per flow rate requirements of the vehicle’s engine and fuel pump. See company website for nitrous oxide use and alternate plumbing schematics. See diagram on next page as well as diagram below,
to identify the ports used on the regulator. Pressure is regulated by the regulator to the rest of the fuel system (from
outlet ports), by restricting flow through the inlet port. Plumb the Pressure Reference Port using a fitting (Not
Supplied) for “blow-through” carbureted applications only, “blow-through” means that a turbo or supercharger is
used to pressurize the carburetor(s). When this occurs, fuel pressure must be compensated by the change in float
bowl pressure. If motor is naturally aspirated (Normal carbureted application, with float bowl vented to atmosphere)
allow this port to vent to atmosphere, do not plug or plumb to any pressure source. Use of supplied port filter is
shown below. The fuel line used must handle high pressure. The use of fuel line such as stainless steel braided
line and “AN” style fitting connections is recommended. The fuel ports (one –8AN Inlet Port and two –8AN Outlet
Ports) use “AN” or “military” style fittings. This plumbing standard is commonly used with racing and high
performance applications. See step 6 on next page for additional information on this port standard. A fuel filter with
a 40 micron or lower particle rating is required to be used upstream of regulator and downstream from fuel pump to
protect it and the carburetor from foreign object damage. Reference the Schematic Diagram below for filter
locations. Use of a liquid filled gauge exposed to engine compartment heat is not recommended as the liquid inside
the gauge may exert measurement errors. DO NOT plumb gauge port to any gauge mounted insid e the vehicle or
in passenger compartment. A line burst can spill fuel inside passenger compartment and on occupants, possibly
causing serious injury or death. An electric gauge or pressure transducer system is recommended for readings in a
passenger compartment.
Typical Carbureted Fuel System Schematic Diagram:
Typical Dual Inlet
Carburetor Shown
Specifications and Recommendations.
55501-c Regulator
Installation Steps:
Follow Fuel Cell Manufacturer's
Recommendations for Proper
Vented Fuel Cell or Fuel Tank.
Tank must be Plumbed According
to Maximum Pump Flow Rate.
Consult Pump Manufacturer's
Fuel Straining Filter Required, Typical
75 Micron Filter Recommended. Straining
Consult Pump Manufacturer's Specifications.
Micron Rating: 75-150, Fuelab
Filter may be Installed in Fuel Pump,
Fuelab Prodigy 40402 Series
Fuel Pump Recommended.
Fuel Filter with 60 Micron or
Lower Particle Rating is Required.
Fuelab Filter with 6, 10 or 40
Micron Rating is Recommended.
Fuel Pump,
Cell Vent Plumbing
1. Disconnect the ground terminal from battery and allow the vehicle’s engine and exhaust system to cool.
Relieve fuel system per applicable service manual. Follow all Warnings and Cautions written on previous page
of these instructions.
2. Modify, remove or replace other fuel system components as required per establi shed build plan (reference
notes on previous page and above).
3. Use the supplied bracket as a drilling template to mark holes for mounting bracket. Choose a location that
minimizes exposure to excessive heat, near carburetor(s). Mounting bracket can be modified as required.
105020521-1, Rev A Sheet 2 of 4
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