PGM-FI for 4-stroke 50cc
scooters
We would like to actively
introduce environmental
technology into the vehicles
being used by many people.
By so doing, we wish to
contribute to the improvement
of the global environment
even if a little. Here is the
basic stance of Honda for
environmental technologies
including fuel consumption
and cleaner exhaust gas.
Asaka R&D Center evolved
PGM-FI technology developed
for small displacement
engines like the 125cc, and
developed a new
electronically-controlled fuel
injection device, PGM-
FI,suitable for use in 4-stroke,
50cc scooters, presently
marketed by Honda as "Clean
4".
First in the World as Mass-
produced 4-stroke, 50cc
Engines
The electronically controlled
fuel injection system, PGM-FI,
with enhanced fuel
consumption and cleaner
exhaust gas has been
developed for mass-produced
4-stroke 50cc engines for the
first time in the world.
Through this technology,
further reduction of fuel
consumption and cleaner
exhaust gas will be promoted
for 50cc class engines which
comprise the greatest sales in
the domestic market.
Technological Features
The most outstanding feature
is the integration of the ACG
starter control and the PGM-FI
into one ECU through
mounting a CPU as high as
32bits.
In addition, new
technologies were developed
aiming at mounting on 50cc
scooters, including new
injectors; ultra-small fuel
pumps and new circuit system
for kick-starting. Additionally,
the number of parts were
reduced from 15 to 8 as
compared with the PGM-FI
designed for large models
through the efforts of
integrating various functional
parts, consolidating sensing
functions and new designs of
major parts including fuel
pumps. A low-cost, compact
and lightweight electronically
controlled fuel injection
system was realized.
Function-integrated ECU
Functions have been
consolidated to achieve low
cost through adopting a high
speed 32bit CPU and
integrating PGM-FI control
ECU with the ACG starter
control ECU. As compared
with the conventional 16bit
CPU, processing speed was
increased by 3.5times and
memory capacity doubled,
which enabled the integration
of the FI control and ACG
starter control into one ECU.
Compared with ECU designed
for conventional 50cc
scooters, the size was reduced
by 21%.
32bit New ECU Performance of 32bit CPU
Compact Fuel Pumps
To maintain a flat floor for
50cc scooters, ultra-small fuel
pump modules were newly
developed, which could be
housed in a flat gasoline tank
located under the floor.
Adoption of a 10µm primary
filter of the highest density in
the world resulted in a
substantial reduction in the
number of parts and in the
realization of compactness
and light weight. Furthermore,
power savings and high
efficiency were achieved
resulting in a rating level of
1A.
New Injectors
The amount of gasoline
required for combustion in
small displacement engines
like 50cc is extremely small
and the small amount of
gasoline must be burned as
efficiently as possible. It is
required therefore for fuel
injectors to make a minute
amount of injection consistent
with the atomization of fuel
spray. It has been general
practice before to have
multiple injection holes for the
purpose of atomization.
In the
injector developed this time
for 50cc engines, the world's
highest level of atomization
was achieved by optimizing
the form of internal passage
of the injector with two
injection holes, to reduce the
amount of injection to a level
of 1/3 of 125cc scooters.
Twin-hole
injector
Comparison of minimum
amount of injection
Atomization performance of
highest level in the world
Idle air control valve
The amount of minimum
controlled air at times of
idling, etc. also needs to be
reduced to one third of 125cc
scooters. In the air valves
developed this time for 50cc
engines, it has been made
possible to control optimum
amount of air for the
conditions of engine
operations like starting,
warming up and idling by
minutely operating a high-
precision valve with an ultra
small step motor in units of
30µm. As the result, a
substantial improvement was
realized in the ease of starting
and idling performance and
maintenance was made
unnecessary for secular
changes.
Control of kick-start
In starting conventional
engines based on a carburetor
system, the pistons were
operated by cell motors or by
kicks and the negative
pressure and mechanical
throttle actions sucked fuel
out. In the electronically
controlled fuel injection
system, however, electric
power is required to inject
fuel for the start of engines.
For small motorcycles like
50cc scooters, kick-starts are
required in case of complete
discharge of batteries after
having been stoked for a long
time. In the PGM-FI newly
developed for 50cc scooters,
engines will start with a small
electric current created by
kicking, which was difficult in
the conventional FI system.
Reliable engine starting was
made possible by kicking even
when the batteries have gone
dead, by the development of a
system to supply power
generated by kicking in a
fraction of a second to only
the circuit required for
starting and power saving fuel
pumps.
By kicking, the ACG will
generate power. The little
power generated will be
supplied with priority to the
circuit for ignition and fuel
injection, shutting off circuits
to batteries and lights. The
time effective for the purpose
is approximately 0.2 seconds,
which is equivalent to about a
stroke of suction,
compression, explosion and
exhaust, or to 2.5 times of
crank rotation by kicking.
Merits of PGM-FI for 50cc
scooters
Engines equipped with newly
developed PGM-FI for 50cc
scooters have contributed to
cleaner exhaust gas and a
largely improved fuel
consumption rate. According
to data during the
development stage, CO and
HC exhaust gas achieved the
level of half of domestic
control and improvement was
realized in fuel consumption
equal to 7% in steady speed
mode and 10% in actual drive
mode*. Moreover, high power
performance, reliable starting
quality and idling performance
were realized.
*In-house test mode assuming
actual conditions of use.
The Development Team of
Asaka R&D Center promoted
development efforts to
achieve Honda's goal of
"switching to fuel injection for
50cc scooters by the year
2005", which was made public
in 1999 and the team
successfully achieved the
dream one year earlier than
the original goal. The
technology will enable Honda
to install PGM-FI on all
motorcycles Honda will
market all over the world.
Honda set new goals for
"installing PGM-FI on all
scooters sold in the domestic
market by the fiscal year
2007" and "installing PGM-FI
on majority of models over
the entire world by the end of
year 2010". Honda's
motorcycles are loved by a
great many people throughout
the world. Honda hopes to
contribute to environmental
improvement of global scale
through further refinement of
his environmental technology.
Honda Worldwide Home Motorcycle Picture Book Technology Close-up Fuel Injection System for Small Engines
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