Mitsubishi 3B2 engine

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Mitsubishi i 2.jpg
Manufacturer Mitsubishi Motors
Production 2005–present
Cylinder block alloy Aluminum die cast
Cylinder head alloy Aluminum die cast
Valvetrain Direct acting DOHC, 12 valves, continuously variable MIVEC intake valve timing
Length 286 mm
Height 191 mm
Dry weight 67 kg
Predecessor Mitsubishi 3G8 engine

The Mitsubishi 3B2 engine is a family of all-alloy three cylinder engines developed by Mitsubishi Motors, first produced in December 2005 at the company's Mizushima powertrain facility in Kurashiki, Okayama,[1] for introduction in their 2006 Mitsubishi i kei car. All engines developed within this family have aluminum cylinder block and head, double overhead camshafts, four valves per cylinder, and MIVEC continuous variable valve timing.[1][2]

The preliminary version of the 659 cc engine was first seen in the "i" Concept test car introduced in 2003, and used Mitsubishi's Smart Idling system which turns off the engine automatically when the vehicle is stationary, and can restart it within 0.2 seconds.[3] So equipped, Mitsubishi claimed the prototype was capable of fulfilling the "three litre initiative" for gasoline engines, meaning fuel consumption of no more than 3.0 litres per 100 kilometres (94.2 mpg, 78.4 U.S. mpg).[3]

The larger 999 cc capacity of the development engine was outside the limits of the kei class in Japan and was introduced in the second generation of the smart fortwo.[4]

The 3B20 was designed with the "rear midship" layout in mind. The basic dimensions chosen reduced the powerplant's height, the cylinder block's structure was simplified, a timing chain was adopted, modularized components were used for the oil and water pumps, engine mounts, and fuel system.[1] The aluminum construction and lightweight parts and materials in the manifolds helped reduce the weight of the engine by 20 percent compared with its iron-block 3G83 predecessor, while gains were also seen in torque, fuel economy and emissions.[1]



Engine type Three cylinder, OHC
Displacement 659 cc
Bore x stroke 65.4 x 65.4 mm
Compression ratio 10.8:1
Fuel type Regular unleaded gasoline
Peak power 38 kW (52 PS) at 7000 rpm
Peak torque 57 N·m (42 lb·ft) at 4000 rpm


Engine type Three cylinder, DOHC, turbocharger
Displacement 659 cc
Bore x stroke 65.4 x 65.4 mm
Compression ratio 8.8:1
Fuel type Regular unleaded gasoline
Peak power 42 kW (57 PS)–48 kW (65 PS) at 6000 rpm
Peak torque 85 N·m (63 lb·ft)–95 N·m (70 lb·ft) at 3000 rpm

3B21-smart fortwo (North American version)[edit]

Engine type Three cylinder, DOHC
Displacement 999 cc
Bore x stroke 72.0 x 81.8 mm
Compression ratio 10:1
Fuel type Premium unleaded gasoline
Peak power 50 kW (68 PS) at 6000 rpm
Peak torque 92 N·m (68 lb·ft) at 3000 rpm

See also[edit]


  1. ^ a b c d "Newly Developed Three-Cylinder MIVEC Engine", Yukihiro Ryugo, Hiroaki Miwa, Mitsubishi Motors Technical Review, 2006, no.18, pp.95–97
  2. ^ "Development of Mitsubishi “i” Powertrain", Hirofumi Higashi, Kuniaki Kaihara, Hideki Miyamoto, Masayuki Takagaki, Kazuteru Kurose, Satoshi Yoshikawa, Hideo Nakai, Masayuki Yamashita, Mitsubishi Motors Technical Review, 2004, no.16, pp.45–50
  3. ^ a b "Development of “i” Concept Test Car for 2003 IAA and 2003 Tokyo Motor Show", Yoshinaka Kawakami, Takanori Yoshii, Mitsubishi Motors Technical Review, 2004 no.16, pp.29-50
  4. ^ "Mitsubishi Motors and smart sign agreement on engine supply", Mitsubishi Motors press release, Tokyo, October 28, 2005