Marine

Wärtsilä's new 31 becomes the most efficient 4-stroke diesel engine in the world

Wärtsilä's new 31 becomes the ...
The name Wärtsilä 31 refers to its 31 cm piston bore
The name Wärtsilä 31 refers to its 31 cm piston bore
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Wärtsilä 31 – the world's most efficient diesel 4-stroke engine
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Wärtsilä 31 – the world's most efficient diesel 4-stroke engine
Wärtsilä 31 – dimensions and specifications
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Wärtsilä 31 – dimensions and specifications
The name Wärtsilä 31 refers to its 31 cm piston bore
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The name Wärtsilä 31 refers to its 31 cm piston bore
Standing 15 feet high, the Wärtsilä 31 is unlikely to find its way into a drag race car
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Standing 15 feet high, the Wärtsilä 31 is unlikely to find its way into a drag race car
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Finnish engine manufacturer Wärtsilä must be a fascinating place to visit. The company manufactures some of the most mind-bendingly enormous marine diesel engines in the world, like the record-breaking, 89-foot high, 44-foot long, 110,000 horsepower RTA96-C we wrote about more than 10 years ago. Now, Wärtsilä has another entry in the Guinness Book of Records ... for the world's most efficient 4-stroke diesel engine.

Designed for medium-sized ferries and cruise ships, or small to medium tankers and container ships, the new Wärtsilä 31 engine isn't nearly as huge as the mammoth RTA96-C. It stands a more modest 15.4 ft (4.7 m) tall in its highest configurations, and 28.8 ft (8.7 m) long in its longest. The cylinder bore is 12.2 inches (31 cm), and the stroke is 16.9 in (43 cm). In its largest V16 format, it makes up to 13,142 horsepower.

Wärtsilä 31 – the world's most efficient diesel 4-stroke engine
Wärtsilä 31 – the world's most efficient diesel 4-stroke engine

It comes in three versions – diesel, spark-ignited gas and dual fuel – and the diesel version takes advantage of advanced fuel and air injection systems, as well as variable valve timing, to deliver a world record efficiency of just 0.271 pounds per horsepower hour.

To put that in context, the gigantic RTA96-C was the most efficient engine in the world upon its debut, and it uses 0.278 lb/horsepower hour. That's a saving of about 2.6 percent, and while that might not sound like a lot, these things can burn an enormous amount of fuel in a day.

If you were to run the most powerful version of the 31 flat out at maximum power for a whole day, and assume it made the same efficiency figure (it wouldn't, but go with me here), the engine would burn some 85,557 pounds of diesel in 24 hours. So a 2.6 percent saving is going to add up to a heck of a lot of diesel over the service life of the engine.

It's also worth noting that there's no efficiency penalty if you fit Wärtsilä's Nitrous Oxide reduction system to the engine to keep emissions down, which is a requirement for operating in certain areas. And the 31 also saves operators money in maintenance, running some 8,000 hours before it needs its first service.

Next time we're in Finland, we'll have to drop by. The team at Wärtsilä must deal with some incredible engineering challenges to build these impressive machines.

Source: Wärtsilä

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8 comments
equator180
Impressive but what is the RPM range
Milton
these guys need to ghost in a human for scale
Island Architect
Finland seems to have a penchant for fine engineering.
The fellow who was assigned the task to redesign the Rolls Royce Merlin to American Standards and methods at Packard was a Finn having studied at their fine Engineering School.
The Packard became the preferred choice to the dismay of the Brits.
bill
Frank Lee
Sure wish they could scale that level of efficiency down to consumer size.
Scion
Now if we could somehow get this in a motorbike...
fastoy
750RPM.
But the stat I like is the weight. 56 tons for the smallest and 85 tons for the biggest.
Jose Gros
Interesting SFC figure, however, the same was obtained by Mike Hewland in a single cylinder, 500cc, single sleeve-valve distribution, Burt-McCollum type, gasoline engine, as in the interview in the C&D July 1974 issue.
Best results ever with SSV were with a two stroke, compression ignition engine, with the 'open sleeve' concept, no 'junk head', sleeve acting as an annular piston 10% of piston area, 3% of power output via sleeve drive mechanism and crankshaft.
A YT video exists about a Petter Brotherhood SSV in the Wärtsilä line of sizes, in the Anson Engine museum, UK. + salut
JaimeLopez
Wärtsilä engineer here - it is indeed an amazing machine!
And of course, Loz, next time you are in Finland, feel free to drop me a line (firstname.lastname at wartsila.com). I will be pleased to organise a press factory tour for you :)