MHI has improved its power generation efficiency from 44%: NOx=220 ppm to 45.5 %: NOx=320 ppm (O2=0 % adjusted) by applying the Miller cycle technology to one of its best sellers, the MACH-30G gas engines.
The Miller cycle technology is already employed in MHI's smaller GSR gas engines (of outputs between 280 kW and 845 kW), and its application in the larger MACH-30G now means it is being applied across the entire range of gas engines.
On the back of intensified competition in efficiency in the market for large-scale gas engines, MHI focused on the application of the Miller cycle. By optimizing compression ratios and other factors, MHI achieved a power generation efficiency of 45.5 %, outstripping its competitors and becoming the most efficient in the world.
Since introducing these highly efficient MACH-30G gas engines into the marketplace, MHI has secured orders for more than 40 units this fiscal year, and expects there only to be an increase in orders next year and beyond.
The Miller cycle is a system that achieves a substantial driving force and improves energy efficiency. By leaving air intake valves open until pistons are part way up the compression strokes, the compression ratio is lowered and the occurrence of knocking reduced and resultantly just the expansion ratio is increased. Because expansion ratios can be kept the same as conventional cycle engines, the energy that can be drawn is also the same. However as the energy used in compressions has been reduced, the result is a more efficient engine.

Type		MACH-30G	MACH 30G (New version)
Cycle		Conventional cycle	Miller cycle
Rated ourput (generator terminal)	(kW)	3,650~5,750	3,650~5,750
Bore/Stroke	(mm)	300/380	300/380
Revolution (50Hz/60Hz)	(rpm)	750/720	750/720
Efficiency	(%)	42.5(44.0)	45.5
NOx (O2 =0%)	(ppm)	100(200)	320