Explanation of codes
Mitsubishi engines designed since 1970 use a four-digit naming convention:
- The first (digit) signifies the number of cylinders; "2" = straight-2, "3" = straight-3, "4" = straight-4, "6" = V6, "8" = V8.
- The second (letter) formerly referred to the fuel type; "D" = diesel, "G" = gasoline. However, since the 1980s, this has changed. Two engine families were introduced using the letter "A" to denote that all the engines in the family had an alloy cylinder head. Their latest engines, however, do not follow any previous conventions (e.g. 4M4x, 3B2x, etc).
- The third (digit) previously denoted the engine family. Five of the "4Gxx" straight-4 engine families had distinct names; "4G1" = Orion, "4G3" = Saturn, "4G4" = Neptune, "4G5" = Astron, and "4G6" = Sirius.
- The fourth (digit) is the specific engine model within the family. It is not a guide to its place within that family, nor is it a guide to the capacity of the engine.
There may also be supplementary letters after the initial four characters. "T" can indicate that the engine is turbocharged (e.g. 4G63T), "B" that this is the second version of the engine (e.g. 4G63B). Where engine codes are used which include the supplemental letters, the first digit denoting the number of cylinders may be omitted, so 4G63T may be seen as G63T.
Mitsubishi's smallest powerplants, most commonly found in their earliest models in the 1960s:
- 2G — First introduced in the second generation Minica in 1969 to replace the air-cooled ME21 powerplant. While water-cooled, the 2G10 was a two-stroke, like its predecessor. It was complemented in 1972 by a new four-stroke OHC design called Vulcan which saw service throughout the 1970s.
- ME21/ME24 — A 359 cc twin cylinder OHV engine in the 360 pickup truck and the first generation Minica.
- NE19A — The 493 cc twin cylinder engine in the Mitsubishi 500, the first passenger car built by the company after the Second World War.
- 3A9x — The 3A91 used in the new Colt in 2005.
- 3B2x — The 3B20, found in the 2003 Mitsubishi i, uses a 660 cc DOHC with the company's MIVEC variable valve timing and an intercooled turbocharger, and was designed with the aim of exceeding Japan's 2010 fuel economy requirements.
- 3G — Introduced in the 1980s, initially as a 550 cc, and enlarged to 657 cc in 1990 when changes in kei car regulations permitted. High performance versions used a 15v head, and can claim the distinction of being the first production engine to feature five valves per cylinder, beating rival designs from Bugatti, Toyota and Audi to the market by at least a year. The 3G83T in the Minica Dangan was the first turbocharged kei car available in Japan.
Mitsubishi has developed twelve families of straight-4 engines:
- 4A3x — A 660 cc engine designed for kei cars in 1994, enlarged to 1100 cc in 1999.
- 4A9x — A 1.3 and 1.5 L engine introduced in the 2003 Colt.
- 4B — The newest family of straight-4 engines being developed in a joint-venture with DaimlerChrysler and Hyundai known as the Global Engine Manufacturing Alliance (GEMA), all featuring aluminum engine block, DOHC heads, 4 valves per cylinder and MIVEC variable valve timing. The first of these are the 4B11 2.0 L and 4B12, a 2.4 L fitted to the 2007 Lancer and Outlander.
- 4DRx — Two 2659 cc straight-4 normally aspirated and turbodiesels, 4DR5 and 4DR6, fitted to some Canter light trucks, and also fitted to the company's Jeep which it built under licence from Willys between 1953 and 1998,
- 4G1x "Orion" — 1.2 L to 1.6 L. First introduced in the 1978 Colt, and now the basis for the high performance variant of the 2003 version.
- 4G3x "Saturn" — Ranging in size from 1.2 L to 1.8 L, this family first saw service in the 1969 Colt Galant.
- 4G4x "Neptune" — 1.2 L to 1.4 L straight-4 engines available in the Lancer and Galant in 1979.
- 4G5x "Astron" — Offered from 1972 in capacities from 2.0 L to 2.6 L, the Astron family pioneered the modern use of twin balance shafts in a straight-4 configuration. The system, introduced in 1975 and dubbed "Silent Shaft", built on the patents of Frederick Lanchester which Mitsubishi had obtained, and proved a lucrative venture when it was licensed to numerous other manufacturers.
- 4D5x "Astron" diesel — Also part of the "Astron" family, the 2.3 L was the first diesel engine to be fitted to a Japanese passenger car. The subsequent 2.5 L version, introduced in 1986, is still in production, a popular choice in its line of pickup trucks where it is regarded as rugged, reliable and inexpensive to maintain.
- 4G6x "Sirius" — Available in capacities from 1.6 L to 2.4 L, this was the favoured performance variant for Mitsubishi. The 4G61T powered their Colt Turbo, while the 4G63T, first introduced in the 1980 Galant, went on to see service in the Sapporo and Starion coupés during the so-called "turbo era" of the 1980s, before creating for itself an illustrious motorsport heritage as the powerplant under the hood of the World Rally Championship-winning Lancer Evolution. A UK-market Evo known as the FQ400 had a 298 kW (405 PS) version of the Sirius, making it the most powerful car ever sold by Mitsubishi.
- 4G9x — 1.5 L to 2.0 L. The first modern gasoline direct injection (GDI) engine, in the Mitsubishi Carisma, was an 1834 cc 4G93 straight-4.
- 4M — Mitsubishi's replacement for the "Astron" diesel, available as a 2.8 L, and later as a 3.2 L with direct injection.
- KE — A range of OHV straight-4s powering the Colt range in the 1960s.
Mitsubishi has three families of V6 engines, which have seem use in its midsize lines, coupés and compacts.
- 6A — The smallest of these, the 1.6 L, was introduced in the Mitsubishi Mirage MX in 1992, and remains the smallest modern production V6. Larger versions powered the higher-spec versions of their family cars, with both the 6A12 2.0 L and the 6A13 2.5 L being given twin-turbo setups for the latter generations of the Mitsubishi Galant VR-4.
- 6B — The newest family of V6 engines featuring DOHC and SOHC heads and MIVEC variable valve timing. The first of these is the 6B31 3.0 L fitted to the 2007 Outlander.
- 6G "Cyclone V6" — First seen in the 1986 Debonair and Diamante as a 2.0 L and 3.0 L, it has been the flagship powerplant of the company except when they briefly built a V8 in 1999-2001. The staple of their high-end sedans, it was given twin-turbos for the Mitsubishi GTO, and became the most powerful car ever built by the company at the time. Subsequent 3.5 L versions were also popular in their SUV range, especially with GDI. Now expanded to 3.8 L with the 6G75 which underpins the newest versions of the Galant, Eclipse and Australian-built Mitsubishi 380.
- KE64 — A straight-6 derivative of the KE4x straight-4 engines developed for the first Debonair from the 1960s Mitsubishi Colt.
- "Saturn 6" — A 2.0 L straight-6 variant of the Saturn straight-4 was made for the Mitsubishi Debonair in the 1970s to replace the KE64.
- 8A — For its Japan-only Proudia and Dignity models, Mitsubishi built an alloy-headed 4.5 L V8 with GDI. The vehicles proved unsuccessful, and were quickly discontinued. However, the range had been developed in conjunction with the Hyundai Motor Company, whose Hyundai Equus fared much better.
- GEMA engine — See the 4B range above.