The OM639 is a

turbocharged In an internal combustion engine, a turbocharger (also known as a turbo or a turbosupercharger) is a forced induction device that is powered by the flow of exhaust gases. It uses this energy to compress the intake air, forcing more air into the ...

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

produced by

Mercedes-Benz Mercedes-Benz (), commonly referred to simply as Mercedes and occasionally as Benz, is a German automotive brand that was founded in 1926. Mercedes-Benz AG (a subsidiary of the Mercedes-Benz Group, established in 2019) is based in Stuttgart, ...

, in collaboration with

Mitsubishi Motors is a Japanese Multinational corporation, multinational Automotive industry, automobile manufacturer headquartered in Minato, Tokyo, Japan.

Design

The OM639 is based on the

four-cylinder The engine configuration describes the fundamental operating principles by which internal combustion engines are categorized. Piston engines are often categorized by their cylinder layout, valves and camshafts. Wankel engines are often categoriz ...

OM640 engine and features a dual mass flywheel,

exhaust gas recirculation In internal combustion engines, exhaust gas recirculation (EGR) is a nitrogen oxide () emissions reduction technique used in petrol engine, petrol/gasoline, diesel engines and some hydrogen internal combustion engine vehicle, hydrogen engines. ...

, and Euro 4 emission standard compliance. It is transversely mounted behind the front axle and inclined 60 degrees due to the sandwich floor design used in the

Smart ''SMart'' was a British CBBC television programme based on art, which began in 1994 and ended in 2009. The programme was recorded at BBC Television Centre in London. Previously it had been recorded in Studio A at Pebble Mill Studios in Birmingha ...

and

Mitsubishi The is a group of autonomous Japanese multinational companies in a variety of industries. Founded by Yatarō Iwasaki in 1870, the Mitsubishi Group traces its origins to the Mitsubishi zaibatsu, a unified company that existed from 1870 to 194 ...

models, so the engine slides underneath the floorpan instead of into the cabin in the event of a

head-on collision A head-on collision is a traffic collision where the front ends of two vehicles such as cars, trains, ships or planes hit each other when travelling in opposite directions, as opposed to a side collision or rear-end collision. Rail trans ...

to improve safety.

Models

OM639 DE15 LA R

* 2004–2006 Smart Forfour 1.5l CDI * 2004–2009 Mitsubishi Colt 1.5 DI-D

OM639 DE15 LA

* 2004–2006 Smart Forfour 1.5l CDI * 2004–2009 Mitsubishi Colt 1.5 DI-D

Reception

Due to the relatively low sales of the cars the engine was placed in to (compared to the class leaders), the engine is in a niche between owners. At the time, the 70 kW version was the world's most powerful three-cylinder

passenger car A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people rather than cargo. There are around one billio ...

. Despite this, it was only used in the

Smart Forfour The Smart Forfour (stylized as "smart forfour") is a city car (A-segment) marketed by Smart (marque), Smart over two generations. The first generation was marketed in Europe from 2004 to 2006 with a front-engine configuration, sharing its platform ...

(until discontinuation) and the

Mitsubishi Colt The Mitsubishi Colt is a nameplate from Mitsubishi Motors that has been applied to a number of automobiles since 1962. It was first introduced with a series of Kei car, kei and subcompact cars in the 1960s, and then for the export version of the ...

(until its facelift in 2008, citing lack of demand). Today, the most powerful three-cylinder

is the BMW B37, which achieves 116 hp. The engine is reliable, with no common issues or widespread issues noted by owners, and no recalls issued. Lastly, real world MPG is very close to Mitsubishi's numbers out on the road, with it getting over 90% of its rated official MPG of 58.9 rated by owners of the vehicles.

References

{{reflist OM639 Diesel engines by model Straight-three engines Mitsubishi Motors engines