An Affordable Fuel Injection System for Small Engines.

J. Allen

Scion-Sprays Ltd, Hethel Engineering Centre, Norwich, NR14 8FB, UK.

Tel   +44 (0)1953 859110		E-Mail   j.allen@scion-sprays.co.uk

Pulse Count Injection Technology (PCI):

PCI uses a small geometrically fixed volume to repeatedly inject an
identical amount of fuel (“pulse volume”) into the engine intake
manifold a number of times each engine cycle.

 

Figure 1. Concept of a PCI injection process shown for a single engine
cycle.

The total number of pulses (“count”) of injected fuel determines the
total amount of fuel delivered to the engine each engine cycle, as shown
in Fig 1.

In order to achieve this fuel flow control process the injector is
constructed as a simple positive displacement pump, with a solenoid
driven piston and cylinder working as the fixed volume displacement
unit. Two one-way check valves ensure the correct flow path of the fluid
into and out of the injector. In this arrangement the single injector is
both a pumping unit and the flow metering unit which can be supplied
with fuel directly from the fuel tank.

The PCI Technology therefore contains fewer parts at a significantly
lower cost than a conventional injection system, but still delivers an
accurately controlled volume of fuel to the engine each cycle. 

Because of the straightforward pulsed nature of the PCI solution the
electronic controls of the system can also be extremely simple and thus
very low cost.

Figure 2. Image of the PC Injector, Fuel Injection module and the
complete Fuel Injection system.

The modular design of the PCI Technology allows the complete fuel
injection system to be fitted into a single housing combined with the
throttle body, delivering a single component system that is very well
sealed against the harsh environments often encountered by small
engines. The electronic control offered by PCI Technology also forms a
perfect platform for a low cost solution to end-user requirements such
as; easy start, smooth response to load changes and simple maintenance.
Also by delivering optimised fuel quantity under all operating
conditions it minimises fuel consumption and emission output. Figure 3
shows an example of emission reduction of 10% achieved through fuelling
optimisation.

Figure 3. Emission Results comparison

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RIA-2006

May 2006

Pulse volume is geometrically fixed

Count number is simple to control

Fuel quantity delivered = pulse volume x count

Start of Injection Burst

Pulse Count Variation

Individual Pulses

