Mitsubishi Heavy Industries Technical Review Vol. 54 No. 1 (March 2017)45

K type Engines for Forklift Trucks and Gas Heat Pumps

G l o b a l C o m p o n e n t Te c h n o l o g yCorporation

Global Component Technology Corporation (hereinafter GCT) is a wholly-owned subsidiaryof UniCarriers Corporation, which is a group company of Mitsubishi Heavy Industries Forklift,
Engine & Turbocharger Holdings, Ltd. (M-FET). GCT has been developing, producing, and sellingindustrial machinery engines since its time as the Industrial Machinery Division of Nissan MotorCo., Ltd. One of their main products is the K type, a 2.0-liter class, spark-ignited, in-line
four-cylinder engine mainly for forklift trucks and gas heat pumps (GHP). This paper presents thefeatures of the K type engine.

|1. Summary of GCT's industrial machinery engines
GCT's engines, based on proven, sophisticated engines for automobiles over the years, havebeen optimized by new designs for forklift trucks and GHP applications in response torequirements and customer needs.
Common requirements include the capability to deal with gas fuel that has fewer lubricating
components in comparison to gasoline and diesel fuel, the durability and reliability suitable forvarious use conditions and environments, the enhancement of fuel efficiency and thermalefficiency, etc.
The K type engine, which is based on knowledge and technologies cultivated throughlong-term results and experiences of the preceding H type engine, was brought to the market as anengine exclusively for industrial machinery in 2003 after understanding various market needs
through use of the QFD (quality function deployment) method and an overall review of the design.
Thereafter, variations were added and improvements were made based on market and customer
needs. Figure 1 shows the main variations of K type engines.

Figure 1 Variations of K type engine

Mitsubishi Heavy Industries Technical Review Vol. 54 No. 1 (March 2017)46|2. Engines for forklift trucks
There are two types of K type engines for forklift trucks: electronically controlled andmechanically controlled. Each of the two includes LPG fueled, gasoline fueled, and LPG/gasoline
combination fueled types based on the type of fuel used.
There are three variations of engine displacement (1.5-liter, 2.1-liter, and 2.5-liter), and theyutilize a common packaging to enhance efficiency for installation on vehicles. These engines aresupplied to many foreign forklift truck manufacturers, as well as all domestic forklift truck
manufacturers other than Toyota Motor Corporation, including Mitsubishi Nichiyu Forklift Co.,
Ltd. and UniCarriers Corporation, which are M-FET group companies.
Table 1

Displacement(cc)

Bore x Stroke(mm)FuelCompression ratio

Specifications of engines for forklift trucks

K21
Non-electronicallyElectronicallycontrolledcontrolled
2065
2065

K25
Non-electronicallyElectronicallycontrolledcontrolled
2488
2488

89.0×83.0

89.0×83.0

89.0×100

89.0×100

Gasoline & LPG

Gasoline & LPG

Gasoline & LPG

Gasoline & LPG

8.7

8.7

8.7

8.7

Rated power output

(kW)

31.2

41

35.6

46.9

Rated engine speed(min-1)

2200

2700

2250

2700

Table 1 shows the engine specifications. The features of the electronically-controlled type,as a representative example, are described below.
(1) Capability to deal with gaseous fuel (LPG)
Parts specifications are optimized in order to secure durability and reliability for use withgaseous fuel.
[1] Intake and exhaust valves[2] Valve seats and valve guides[3] Piston rings(2) Control system
Figure 2 shows a control system of an engine for forklift trucks. An engine for forklift
trucks requires governor control of the engine rotation speed in order to protect the hydraulicpump for cargo handling. To meet this requirement, independent governor control of theelectronically-controlled throttle chamber is adopted.

Figure 2 Control system of engine for forklift trucks

Mitsubishi Heavy Industries Technical Review Vol. 54 No. 1 (March 2017)47

In addition, GCT's unique LPG gas injection TBI (throttle body injection) system isadopted. The fuel efficiency and the operability are enhanced, the exhaust gas is cleaned,
gasoline/LPG combination fuel control is adopted, maintainability is enhanced using theself-diagnostic control and vehicle speed limiting control, which contributes to the safe
operation of the forklift truck, is adopted.
(3) Output performance
For engines for forklift trucks, torque at low and middle engine rotation speeds is more
important in comparison to automotive engines. For this reason, the following were optimized:[1] Shape of combustion chamber[2] Compression ratio[3] Shape of intake manifold[4] Valve timing|3. Engines for GHP
Table 2 shows the specifications of engines for GHP. Optimizations to meet therequirements of engines for GHP were made while progressing with communalization with engines
for forklift trucks.
(1) Enhancement of thermal efficiency
To attain the the highest thermal efficiency in the region of GHP usage, the following
specification enhancements were made.
[1] Shapes of combustion chamber and intake and exhaust ports[2] Increase of compression ratio[3] Optimization of valve timing (mirror burn)[4] Lean burn(2) Enhancement of durability
Engines for GHP are required to have higher durability in comparison to vehicle engines
and forklift truck engines because of their many hours of continuous operation. Therefore, thefollowing specification enhancements were made.
[1] Improvement of the valve sliding parts (valve seats and valve guides)[2] An ignition system that deals with the higher secondary voltage required by lean burnoperation[3] Enhancement of starter specifications in response to increased frequency of switching
the engine on/off
Table 2

Specifications of engines for GHP
K21K25

16PS

30PS

20PS

16PS

Displacement

(cc)

2065

2488

2488

2488

Bore x Stroke(mm)

89.0×83.0

89.0×100

89.0×100

89.0×100

13A, LPG

13A, LPG

13A, LPG

13A, LPG

13.5

14.0

14.0

15.5

Fuel
Compression ratio
Rated power output

(kW)

14.0

21.0

15.8

15.2

Rated engine speed-1

1900

2000

1500

1800

(min )|4. Future prospects
Currently, strict exhaust gas regulations have been applied to spark ignition type engines forforklift trucks in Japan and North America. In 2019, further stringent exhaust gas regulations will
also be introduced to Europe. We hope to support the development of the industrial machinery
business by evolving our products to contribute to further cleaner exhaust gas and the reduction of
CO2 in consideration of global environmental protection.