Press Information

MHI Develops One of World's Most Efficient Gas Engine "MACH II-SI,"
A 66.1% Efficiency of Power Generation Plus Energy Recovery from Steam
-- Spark Plug Ignition System Adopted to Eliminate Auxiliary Pilot Fuel --


Tokyo, February 12, 2009 - Mitsubishi Heavy Industries, Ltd. (MHI) has developed and begun operational verification testing of the "MACH II-SI," a new gas engine featuring enhanced energy efficiency and reliability. The MACH II-SI was developed based on the company's existing "MACH-30G," which many units have been sold in Japan; but whereas the forerunner uses a "micro-pilot ignition" system, the new MACH II-SI adopts a spark ignition (SI) system that eliminates the need for auxiliary liquid pilot fuel such as light oil.

Gas Engine "MACH II-SI,"
In developing MACH II-SI, MHI focused on further enhancement of the efficiency leveraging its abundant experience accumulated in its existing engines. As a result, the new engine has achieved efficiency – combining power generation and heat energy recovery via steam – of 66.1%*, the world's highest level among 6,000 kilowatts (kW) class engines, in which electric power generation efficiency has been improved by 1 percentage point. MHI expects the MACH II-SI series, which power output ranges from 3,650 kW to 5,750 kW, will significantly contributes to increasing needs for CO2 emission reduction.

To enhance overall efficiency, MHI focused on enhanced heat recovery in steam generation and effective utilization of exhaust gas energy. The company also has shortened lead-time to reach full load after engine start by 50%, which contributes to enhance load-following capability. In order to boost power generation efficiency, MHI redesigned the combustion chamber, including the cylinder cover and piston. By optimizing formulation of the fuel-air mixture, as well as improving the pre-chamber's shape and fuel-air mixture ratio, the company has raised combustion efficiency and reduced thermal loss.

In developing the technology used to achieve these improvements, MHI applied results gained from "Development of Technology for Ultra High-efficiency Natural Gas Engine Combined System," a joint development project under way since 2005 together with the New Energy and Industrial Technology Development Organization (NEDO) and the Japan Gas Association. Going forward, the new technologies employed in the MACH II-SI to enhance power generation efficiency will also be applied to existing MACH engines with the micro-pilot ignition system.

MHI conducted the testing of the actual MACH II-SI engine – to confirm start-up performance, engine performance and control system – last summer at the company's Yokohama Machinery Works. As all targeted goals were achieved, the new engine has now progressed to the next stage of testing, including durability testing, toward final verification of its enhanced reliability.

Since its introduction in 2001, MHI has delivered more than 150 units of the MACH gas engines, which were developed based on the "KU30" diesel engine―some of the KU30 units have already operated more than 170 thousand hours. In addition to new technologies, the know-how and expertise accumulated through this abundant operational experience have been incorporated into the MACH II-SI to ensure high reliability. MHI has also established the "Customer Service Center" at the Yokohama Works to provide 24-hour, 7-days-a-week remote support service on a contract basis for operational supporting of user plants as well as emergency services. The company has also strengthened its service network, established service centers in Hiroshima and Nagoya to serve customers in western and central Japan region, respectively.

Through establishment of a coherent, integrated structure in one site - from development to designing, manufacture and services, MHI will further enhance its prompt responsiveness to customers' needs and accelerate technological innovation in a timely manner.

* Note: The efficiency of 66.1% was achieved under the terms of ISO 3046 using gas with a methane number of 80, the standard quality of gas MHI recommends.

About MHI Group

Mitsubishi Heavy Industries (MHI) Group is one of the world’s leading industrial groups, spanning energy, smart infrastructure, industrial machinery, aerospace and defense. MHI Group combines cutting-edge technology with deep experience to deliver innovative, integrated solutions that help to realize a carbon neutral world, improve the quality of life and ensure a safer world. For more information, please visit or follow our insights and stories on