02-01-2013, 11:19 AM
HP EFI 4 BBL MPFI SYSTEMS
MPFI SYSTEMS.pdf (Size: 2.8 MB / Downloads: 99)
INTRODUCTION
Holley has written this manual for the installation of the HP EFI manifold and fuel system. Wiring harness and ECU installation, sensor connections, startup, and tuning are contained on the disc supplied with HP systems. Please read all the WARNINGS, NOTES, and TIPS, as they contain valuable information that can save you time and money. Should you need information or parts assistance, please contact our technical service department at 1-270-781-9741, Monday through Friday, 8 a.m. to 5 p.m. CST. Please have the part number of the product you purchased when you call.
SUPPLY AND RETURN FUEL SYSTEM INSTALLATION
The MPI fuel system is a fuel metering system based on a time/pressure principle. The longer the injector is open the lager the amount of fuel per fueling event is delivered to the engine. Fuel pressure also plays a direct role in how much fuel is delivered to the engine. The higher the fuel pressure the more fuel is delivered during the fueling event. It is crucial for the proper operation of a high performance MPI system that the fuel system be installed and sized correctly. Unlike a carburetor where low-pressure fuel is delivered at an "as need" rate, the MPI supply system must continuously deliver fuel at the correct high pressure in a volume greater than the engine requires at maximum load. The excess fuel the injectors do not use is returned to the fuel tank. At idle, most of the fuel is returned to the tank, but a wide-open throttle (WOT) under full load nearly all of the fuel is used by the engine and only a small amount is returned to the fuel tank. An improperly installed or sized MPI supply fuel system may deliver enough fuel at low engine speeds but will starve the engine at WOT.
Fuel Pressure Regulator
The function of the fuel pressure regulator is to provide constant fuel pressure for the fuel injectors. Constant fuel pressure is essential to ensure an accurate fuel metering process. The fuel pressure regulator of the system is set to 300kPa (43.5 psi) to match the flow characteristics of the fuel injectors. The pressure regulator is reference to the manifold pressure to ensure the required differential pressure for the metering event. Thus at high manifold vacuum (i.e. idle) the fuel pressure gage will read a fuel pressure that is slightly lower than 300kPa (43.5 psi) because the gage is referenced to atmospheric conditions and not to the intake conditions. The pressure reading at idle will vary with the application as manifold vacuum changes from engine to engine and from application to application.
The regulator included is adjustable. To adjust the fuel pressure: remove the vacuum reference line and turn the screw clockwise to increase the pressure (or counter-clockwise to decrease the fuel). Fuel pressure can be lowered slightly or raised to reduce or increase the amount of fuel the injectors add. This is usually only done when the injectors used need to have their flow decreased at idle or increased at wide-open throttle. Make sure you input the actual pressure into the software in the “Engine Parameters” section.