Haltech E6GMX - Manual (Page 105)

E6GMX Manual
105
D.4 Fuel Pump Capacity
You should ensure that your fuel pump is capable of supplying sufficient fuel to feed the
engine at maximum power. With the engine switched off (injectors closed) feed the return
line of the fuel pressure regulator to a measuring container. In the case of a turbo- or
supercharged engine, pressurise the manifold pressure port of the fuel pressure regulator to
the maximum boost of the engine. This is necessary as the flow rate of the pump decreases
with output pressure. Power the pump for one minute and calculate the hourly fuel flow rate
of the pump.
Since the pressure regulator operates on a return system, there should always be fuel being
returned to the tank, even when fuel flow to the engine has reached its maximum. If this fails
to happen, the fuel pressure will fall out of regulation. Therefore the fuel pump must be
capable of delivering significantly more fuel than the engine is going to use. As a guide, the
pump should flow 30% more fuel than consumed by the engine.
If you cannot achieve the required fuel flow from one pump, you can employ two pumps in
parallel. If you choose to use a low-pressure pump to augment the fuel flow of a high-
pressure pump, place a check valve after the low-pressure pump.
D.5 Fuel Rails and Pressure Regulators
A long fuel rail with narrow internal diameter will suffer from pulsation in the fuel rail. The
internal rail diameter should be around 12mm (½"). Even so, oscillations may occur,
particularly if the injectors are large. A fuel damper can help in removing these oscillations. If
running a multipoint set-up, batch fire injection will also reduce oscillation amplitude.
Oscillations may occur only within a certain rpm range, so a fuel pressure meter should be
monitored throughout the driving range of the engine.
On V configuration motors, it may be more practical to employ two regulators, one on each
bank's rail. The fuel from the pump can be split to the two rails, and the return line from the
two regulators can be joined. Since pressure regulators work within certain flow limits, this
may also save having to purchase an expensive high pressure / high flow regulator.