W?rtsil? 31DF

The Wärtsilä 31 is the first of a new generation of medium speed engines, designed to set a new benchmark in efficiency and overall emissions performance.

The Wärtsilä 31 is available in 8 to 16 cylinder configurations and has a power output ranging from 4.2 to 8.8 MW, at 720 and 750 rpm. The launch of the Wärtsilä 31 introduces a 4-stroke engine having the best fuel economy of any engine in its class. At the same time, it maintains outstanding performance across the complete operating range. Its modular design enables a significant reduction in maintenance time and costs, thereby improving power availability and reducing the need for spare parts.

Wärtsilä 31 is recognised by Guinness World Records as the world's most efficient 4-stroke diesel engine.

    The Wärtsilä 31 retains its high efficiency and environmental values throughout the entire lifecycle of the vessel.
    • Lowest fuel consumption over a wide operating range.
    • Highest cylinder power in its segment, 610 kW/cylinder.
    • Available in Diesel, Dual Fuel (DF) and Pure Gas (SG) versions.
    • Meets the coming IMO Tier 3 regulations when operating on gas, and with an SCR when using diesel fuel. The SCR has a minimal effect on fuel consumption.
    • Reliability guaranteed through extensive validation and Wärtsilä’s vast manufacturing experience.
    • Supported by Wärtsilä’s extensive global service network.
    Technical data
    Wärtsilä 31DF IMO Tier III
    Cylinder bore 310 mm Fuel specification: Fuel oil
    Piston stroke 430 mm 700 cSt/50


    7200 sR1/100°F
    Cylinder output 550 kW/cyl ISO 8217, category ISO-F-RMK 700 ISO-F-DMA, ISO-F-DMB, ISO-F-DMZ ,ULSF
    Speed 750 rpm  
    Mean effective pressure 27.1 bar Gas: Methane number ³ 80
    BSEC 7270 kJ/kWh
    BSGC 7100 kJ/kWh
    Piston speed 10.75 m/s
    Engine platform A* A B C F Weight (tons)
    Wärtsilä 8V31DF 6175 6114 3205 3115 1496 56.8
    Wärtsilä 10V31DF 6813 6754 3205 3115 1496 66.1
    Wärtsilä 12V31DF 7900 7840 3137 3500 1496 77.7
    Wärtsilä 14V31DF 8540 8480 3137 3500 1496 85.3
    Wärtsilä 16V31DF 9130 9070 3137 3500 1496 94.1
    Rated power 
    Engine type
    8V31DF 4400
    10V31DF 5500
    12V31DF 6600
    14V31DF 7700
    16V31DF 8800
    W31 technical data W
    Download brochure

    The Wärtsilä UNIC is an embedded engine control system for Wärtsilä 4-stroke engines incorporating decades of experience, knowledge and expertise. It makes engines safe, environmentally energy efficient, reliable and flexible. Read more in the brochure. 

    Wärtsilä UNIC

    Specific fuel energy consumption
    • At ISO standard reference conditions at 85% load
    • Lower calorific value of fuel 42 700 kJ/kg
    • Tolerance 5%
    • With engine driven pumps
    • Natural gas
    • Methane number min. 80
    • Lower heating value min. 28 MJ/Nm3

    The Wärtsilä 31 is designed to be suitable for a broad range of ship types and applications, both as a main propulsion engine and in diesel electric configurations, or as an auxiliary engine. It can be optimised for running either at constant speed or along a propeller curve. In the Offshore sector, the Wärtsilä 31 is a perfect solution for OSV´s and drilling or semi-submersible vessels, where operational flexibility, high power density, long intervals between overhauls, and high levels of safety are of paramount importance.

    Methane Number

    W?rtsil? Methane Number Calculator

    We have developed this tool for ship owners and operators to calculate the Methane Number of the fuel gas.
    The calculation result indicates whether or not the given gas quality is suitable for use in W?rtsil? dual fuel engines.

    Methane CH4
    Iso-butane (2-Methylpropane)i-C4H10
    Iso-pentane (2-Methylbutane)i-C5H12
    Neo-pentane (2,2-Dimethylpropane) neo-C5H12
    Mix-hexaneMix C6H14
    Mix-heptaneMix C7H16
    Carbondioxide C02
    Nitrogen N2
    Hydrogen sulfideH2S
    Total mol%
    W?rtsil? Methane number (WMN)
    Propane Knock Index (PKI)
    The calculation tool is owned by W?rtsil? and is made for customer use and is for guidance only. Changes in the tool is reserved at any time.
    Business White Paper - Hybrid propulsion is part of the future for RoPax ferries

    Business White Paper: Hybrid propulsion is part of the future for RoPax ferries

    Green is undoubtedly the colour concept most dominating today’s shipping industry, and nowhere is this more true than in the ferry sector. Environmental considerations are, along with the need to optimize operational efficiency, high on the agenda of ferry operators around the world.

    Hybrid systems are being featured more and more on a variety of vessel types, but are particularly relevant to ferries since they are more likely to be operating within areas covered by strict environmental regulations.

    Download this white paper to get a better understanding of how to select the most appropriate power system configuration for your RoPax or RoRo ferry, not only for today, but for tomorrow as well.

    Shipping in the 2020 era – selection of fuel and propulsion machinery

    Environmental concerns have led to increasingly stringent emission legislation. What started as an onshore industry regulatory development is now impacting also the shipping industry. Shipping has lately faced multiple new regulations, and will soon be facing other major regulations. The global cap of an 0.5% maximum content of sulphur in fuel from 2020, and the IMO Tier III regulations (specifying that NOx emissions must be 80% lower than at the IMO Tier I level) within Emission Control Areas will force the shipping industry to consider alternatives beyond today´s standard solutions.

    Business White Paper - Hybrid propulsion is part of the future for RoPax ferries

    Find out what makes the Wärtsilä 31 tick

    Find out what makes the W?rtsil? 31...

    Next generation automation system enables W?rtsil? 31 performance. Download the brochure.

    Modularisation hand in hand with manufacturability

    The development of the new W?rtsil? 31 engine provided the perfect opportunity to exploit the benefits...
    29 May 2018
    • In Detail article

    Common rail fuel injection rules the...

    Very few marine engines are awarded a Guinness World Record. Thanks to W?rtsil?’s common rail injection...
    28 July 2017
    • Twentyfour7. article


    W?rtsil? 31 - the most efficient engine in the world

    Welcome to a brand-new generation of engines. The W?rtsil? 31 is setting a new standard for energy efficiency, delivering the lowest level of fuel consumption of any four-stroke engine worldwide.
    20 October 2015
    • Twentyfour7. article

    Press releases

    Product hologram


    Contact us

    Please fill in the form, we aim to respond within 1-2 business days depending on the enquiry. For an existing installation, provide all necessary details to identify the installation and the equipment. Fields indicated with an asterisk (*) are required. 

    Find your local Wärtsilä office here

    ? 2020 W?rtsil?