MAN PrimeServ Launching Dual-Fuel Methanol Retrofits for Four-Stroke Engines

Starting in 2025, MAN PrimeServ will offer a retrofit package to convert deployed MAN four-stroke engines to dual-fuel methanol operation. Customers will convert their MAN 48/60 engines to the latest 51/60R-DF-M engine type with methanol capability, with or without a common-rail system. In addition to dual-fuel methanol operation, customers will benefit from higher engine efficiency during diesel operation. The engines will be equipped with MAN Energy’s control and safety systems.

“Climate-neutral shipping can only be achieved with synthetic fuels, and green methanol is particularly suitable for four-stroke applications due to its favorable energy-density,” said Stefan Eefting, Head of MAN PrimeServ Germany. “In this context, we have already received many retrofit enquiries from customers who want to switch to methanol. With our new methanol-retrofit package, we can now offer customers an economically attractive opportunity to convert older engines to a future-proof type.”

According to MAN Energy Solutions, the conversion package has been under development and tested at its Augsburg plant since summer 2024. MAN PrimeServ will perform the first four-stroke engine retrofits for a pilot customer in fall 2025, with the package coming to market shortly after.

51/60R-DF-M engine; Image Credits: MAN Energy Solutions

“We have already gained extensive experience in methanol operation with the MAN 51/60R-DF-M in a series of tests,” said Alexander Knafl, Head of Engineering R&D Four-Stroke at MAN Energy Solutions. “We have achieved pleasing results in both combustion management and methanol injection and are now focusing on further optimization. Our aim is to ensure a consistently high engine-efficiency, regardless of the fuel type—diesel or methanol.”

In April 2024, MAN Energy agreed to deliver three 6L21/31 DF-M generator sets (gensets) for a 7,990 dwt IMO type II chemical bunker tanker’s propulsion system. The dual-fuel gensets will comprise part of a diesel-electric propulsion system for the vessel with electrical motors driving twin fixed-pitch propellers using gearboxes. Dual-fuel generator usage will be optimized with an onboard battery-storage system.

The 21/31 DF-M genset offers the following advantages:

• A port-fuel injection concept that optimizes reliability and reduces capital-outlay time
• Power range spanning 1,000-1,980 kW
• Thousands of units in service, with more than 55 million operating hours

In March, MAN Energy and Svitzer agreed to develop a methanol version of the MAN 175D engine—the 175DF-M—and finalize the field-test agreement in which the engine and plant equipment will be installed on a newbuild tug constructed by Svitzer. The next phase of the partnership, prior to signing the field-test agreement, will outline specifics regarding the fuel-supply system, engine-room design, exhaust after-treatment, and engine-performance optimization.

The design is a high-speed engine capable of operating on methanol fuel and will be available in newbuild or retrofit configuration. It is a product focused on maritime propulsion, equipped with dual-fuel port fuel injection (PFI) technology that is currently undergoing development and validation on two- and four-stroke engines.

MAN Energy’s PFI development goals include:

• High methanol share across a wide power range
• High cylinder outputs
• Zero-carbon footprint with full fuel flexibility