PHR Fuel System |
MKIV
12 Volt Fuel Pump Mod
All lines and hoses are pre-assembled when shipped from PHR
in the same fashion as they are installed on the vehicle.
Please make note of the line connections BEFORE disassembling
the parts. Follow all Toyota procedures for removal of OEM
intake manifold components when installing the PHR fuel system.
Make absolutely SURE all electrical systems are dis-connected
BEFORE beginning work on any fuel system! All work should
be performed by qualified personnel only.
The Concept: The stock fuel
pump on the twin turbo Supra has two modes of operation. There
is a high speed mode for high engine demand, and a low speed
mode for cruising. The fuel pump ECU(seperate from the main
ECU) receives information from the main ECU which determines
which mode the fuel pump should be operating in. Various sensors
come into play to determine when high and low speed operation
should be used. Under idle conditions and cruising, the fuel
pump ECU sends a reduced voltage output to the fuel pump(9
volts), and the fuel pump operates in "low speed". When engine
sensors determine a high engine load, the fuel pump ECU will
send a full 12 volt signal to the fuel pump, kicking it into
"high speed" so that it will supply more fuel.
The Problem: When modifications
are made to the car to increase boost pressure and engine
breathing ability, some owners have experienced detonation
around 4000 rpm, as the 2nd turbo builds boost and comes on
line. Usually, this detonation disappears above 5000 rpm.
The problem is, the fuel pump is still in "low speed" mode
around 4000 rpm's, but the performance modifications have
increased fuel demand to the point of "outrunning" the low
speed operation. By 5000 rpm, the fuel pump ECU has caught
up and switches to high speed operation and all detonation
disappears.
