The Wärtsilä 32 is a medium-speed, four-stroke trunk-piston marine and stationary diesel engine produced by Wärtsilä Finland, with a 320 millimetre cylinder bore and a 400 millimetre piston stroke (the bore-stroke nomenclature within Wärtsilä is generally 320 mm; the engine is referred to in the trade as the W32). The engine has been in continuous production and progressive development since 1981 and is one of Wärtsilä’s two flagship medium-speed product families, together with the larger Wärtsilä 46. Cylinder configurations span six to nine in-line and twelve to eighteen in V configuration, with rated outputs from approximately 3,000 kilowatts to 11,700 kilowatts.
Cylinder data and outputs
The W32 in current rating produces 580 kilowatts per cylinder at 720 or 750 revolutions per minute, with V18 configurations delivering up to 11,700 kilowatts. Brake mean effective pressure on the latest production W32 reaches approximately 27 bar, among the highest in the medium-speed segment, supported by miller-cycle valve timing, two-stage turbocharging on selected variants, and an upgraded combustion chamber and piston ring pack. Available configurations are L6, L7, L8, L9, V12, V14, V16, and V18. The engine is supplied as both a marine main propulsion unit (typically L configurations on a reduction gearbox) and as a marine generator set (typically L or V configurations driving a 720 or 750 revolutions per minute alternator at 60 hertz or 50 hertz markets respectively).
W32DF dual-fuel variant
The Wärtsilä 32DF is the dual-fuel variant capable of operating on liquefied natural gas (LNG) in the lean-burn Otto cycle with diesel pilot injection or on liquid fuel in the conventional diesel cycle. Switchover between fuels is seamless and occurs without load interruption. The 32DF was a key product in the 2010s LNG-fuelled fleet expansion, used on offshore supply vessels, ferries, and dual-fuel cargo vessels. In gas mode the engine meets IMO Tier III without aftertreatment.
W32 methanol variant
The W32 methanol variant, introduced in 2023 as a development of the platform, supports operation on methanol with a small pilot diesel injection. Methanol is a leading carbon-neutral fuel candidate when produced from renewable hydrogen and captured CO2, and Wärtsilä together with MAN Energy Solutions is among the principal suppliers of methanol marine engines to the present orderbook. Several major methanol-fuelled cargo vessels including Maersk’s container fleet retrofits and newbuild orders use Wärtsilä 32 methanol gensets.
Fuel and emissions
The base diesel W32 runs on heavy fuel oil, marine diesel oil, low-sulphur fuel oil, and biofuel blends. IMO Tier II compliance is standard for the diesel variant; Tier III compliance requires either selective catalytic reduction or operation in gas mode (32DF). Wärtsilä’s NOx Reducer (NOR) selective catalytic reduction system is widely paired with the W32 for Emission Control Area service.
Applications
The W32 is one of the most widely deployed medium-speed engines globally. Notable application categories include:
- Container ship and bulk carrier auxiliary gensets at the upper output end (replacing or competing with MAN 32/40, Bergen, and HiMSEN units).
- Ferry and ro-pax main propulsion in mechanical or diesel-electric configurations, particularly Norwegian and Mediterranean services.
- Offshore supply vessels, anchor handlers, and platform supply vessels, often in 32DF dual-fuel configuration.
- FPSO and offshore platform power generation.
- Naval auxiliaries and large patrol craft.
- Land-based power plants in the 6 to 200 megawatt range.
Production and service
The W32 is built principally at Wärtsilä’s Vaasa facility in Finland, with components sourced from a global supplier network. Wärtsilä supports the engine through the Wärtsilä Lifecycle services organisation, with service centres in approximately seventy countries and digital monitoring through the Wärtsilä Expert Insight platform. The engine was the basis for the late-1980s W32A, the 1990s W32E, the 2000s W32 update, and the 2015 reset that bumped output and efficiency through Miller cycle and combustion chamber redesign.