Manual

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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 p ressure will fall out of regulation. Therefore the fuel pump must be
capable of deliverin g significantly more fuel than the engine is goin g 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 p ressure p ump and before the high pressure pump to p revent
an overpressure condition at the output of the low pressure pump.
C.5 Fuel Rails and Pressure Regulators
A long fuel rail with narrow internal diameter will result in fu el p ressure oscillations 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 ran ge, so a fu el p ressure meter
should be monitored across the range of the engine speed and load to detect such problems.
On V configuration engines, it may be more practical to emp loy two regulators, one on each
bank's rail. The fuel from the p ump can be split to the two rails, and the return line from the
two regulators can be joined. Sin ce p ressure regulators work within certain flow limits, this
may also save having to purchase an expensive high pressure / high flow regulator.