Honda PGM-FI for 4-stroke 50cc scooters

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%.

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.

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 Honda 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.

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