Development ofNew Mitsubishi Meiki 4 Stroke'GB Series' Gasoline Engine

General Machinery &Special Vehicle Headquarters(Meiki Gasoline Engine Dept.)

There has been a growing need for a more diverse
range of small general-purpose gasoline engines in themarket for such engines. This is evidenced by the greater
importance being placed on convenience and ease of use
as users become older and in light of a growing shift inusers from men to women in the agricultural machinery,construction, and industrial machinery markets. Various regulatory requirements and standards regarding
the environment in which such engines are used are also
becoming more stringent, as well.
In order to meet such needs, Mitsubishi Heavy Industries, Ltd. (MHI) has reviewed the basic performance
characteristics of such engines from the bottom up, including starting properties, noise and vibration. As aresult of these efforts, MHI has developed a new seriesof small four-stroke engines known as the "GB series",with the aim of providing an engine that is friendly toboth people and the environment and which is easy touse.

maximum output of 3.0 kW, and the GB180 engine witha maximum output of 4.6 kW. Table 1 shows the principal specification data for each model. The title photoshows an external view of a GB100 engine.
(1) GB100 Engine
The displacement in the GB100 engine has been
increased from 80 cc to 98 cc, and output has been
improved by about 25%, while maintaining the engine dimensions at nearly the same values as thosefor the currentGM82 model engine.
In addition, the GB100 engine is designed to meet
two different sets of specifications: those based on theoutput shaft being directly connected to the crankshaft and those based on the 1/2 reduction output
shaft being connected to the camshaft, thereby allowing the engine to be used to fulfill a diverse range ofneeds. The GB100 engine is the industry's only modelin its class that satisfies both requirements.
(2) GB130 and GB180 Engines
The maximum output of the GB130 and GB180 engines has been improved by about 5% compared withcurrent models by improving the cam profile, reducing internal friction, and other measures.

1. Product specifications
The GB series consists of the GB100 engine with amaximum output of 2.2 kW, the GB130 engine with a

Table 1 Specification Data of Engine

GB100

GB130

GB180

Air-cooled four-stroke
inclined type horizontal
shaft OHV gasoline engine

Type

Total piston displacement

(cc)

98

126

181

Cylinder bore x stroke(mm)

1 - 56 x 40

1 - 62 x 42

1 - 68 x 50

Rated output, kW(PS)

1.6 (2.2)

2.3 (3.1)

3.4 (4.7)

Maximum output, kW(PS)

2.2 (3.0)

3.0 (4.2)

4.6 (6.3)

Maximum torque, N - m (kgf - m)

5.35 (0.55)

7.65 (0.78)

11.6 (1.18)

(L)

0.4

0.5

0.6

Fuel tank capacity

(L)

1.6

2.5

3.6

Dry weight(kg)1113.5

15.5

Engine size, L x W x H(mm)285 x 313 x 293

297 x 354 x 329

308 x 365 x 352

Amount of lubricating oil

Mitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 1 (Jan. 2006)1

cooling fan. In addition, seating noise of the intake
and exhaust valves has also been reduced by improving the cam profile. As a result of these reductions, atotal reduction in noise generation of 3 to 4 dB(A) compared with current engine models has been achieved,making the engine top-level in its class in terms oflow noise properties.
(3) Low vibration
The weight of the reciprocating parts has been reduced, thereby reducing vibration forces by about 15%.
Furthermore, the balance ratio of the crankshaft has
been optimized and matching with the working machine has been enhanced.
(4) Clean
Exhaust gas emission levels of the GB series engines conform with various regulations, including theself-imposed regulations of LEMA ( Japan Land Engine Manufacturers Association), regulatory
requirements of EPA (Environmental ProtectionAgency) in the United States, and the Phase 2 regulations of CARB (California Air Resources Board) .
This has been done by improving the combustion
characteristics of the engines by optimizing MHI'sunique pent roof combustion chamber design and thecam profile.

2. Characteristics(1) Easy starting
Improving MHI's original mechanical decompression mechanism has made it possible to reduce therecoil pull force by about 15% compared with current
engine models. Furthermore, the engine has been set
so that it can be started in low external air temperatures of from 10 to 15 oC without the use of a choke
operation by optimizing the setting of a newly designed carburetor. This has made it possible tominimize the need for cumbersome choke operation.
In addition, in order to prevent carburetor problems due to fuel corrosion, top-level industry corrosion
prevention specifications have been equipped as standard. Special consideration has also been given to there-starting properties of the engines after long-term
storage.
(2) Low noise
Based on the structural analysis, the body of thecylinder block has been effectively made highly rigid,
thereby reducing the propagation of vibration. Moreover, mechanical noise has been significantly reducedby changing to prastics from metal parts, adopting a
damping assembling structure, and improving theMitsubishi Heavy Industries, Ltd.
Technical Review Vol. 43 No. 1 (Jan. 2006)

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