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.
| 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.
| 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%.
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.
| 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.
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.