Mitsubishi Saturn engine

The Mitsubishi Saturn or 4G3 engine is series of overhead camshaft (OHC) straight-four internal combustion engines introduced by Mitsubishi Motors and saw first service in the 1969 Colt Galant. Displacement ranges from 1.2 to 1.8 L (1,239 to 1,755 cc), although there was also a rare 2-litre (1,994 cc) inline-six version built from 1970 until 1976. The early versions have chain driven valvetrain while the later versions are belt driven and equipped with balance shafts.

Mitsubishi Motors SVG logo 2.svg Saturn engine
Mitsubishi G32B.jpg
ManufacturerMitsubishi Motors
Also called4G3
ConfigurationStraight-4 & Straight-6
Displacement1.2–2.0 L (1,239–1,994 cc)
Cylinder bore73 mm (2.87 in)
74.5 mm (2.93 in)
77 mm (3.03 in)
79 mm (3.11 in)
80.6 mm (3.17 in)
Piston stroke74 mm (2.91 in)
77 mm (3.03 in)
86 mm (3.39 in)
Block materialCast iron
Head materialAluminium
ValvetrainSOHC & DOHC, 2 valves x cyl.
Compression ratio9.5:1
TurbochargerOn G32B & 4G32T
Fuel systemMikuni-built Solex carburetor
Central-point EFI
Fuel typeGasoline
Cooling systemWater-cooled
Power output37–115 hp (28–86 kW)


The 4G30 displaces 1.3 L (1,289 cc). It is an 8-valve SOHC design with an aluminium head and iron block. The engine has five main bearings. Power was 87 hp (65 kW).

Bore x Stroke: 73 mm × 77 mm (2.87 in × 3.03 in)



The 4G31 displaces 1.5 L (1,499 cc). It is an 8-valve SOHC design with an aluminium head and iron block. The engine has five main bearings. Power was 95–105 hp (71–78 kW) depending on which carburetor combo was used. An updated version with central-point electronic fuel injection was installed in Mirages and Lancers from 1986 on.[1] A version for industrial use has 37 PS (27 kW) at 3000 rpm.[2]

Bore x Stroke: 74.5 mm × 86 mm (2.93 in × 3.39 in)



In 1970, the 4G32 was introduced, and it displaces 1.6 L (1,597 cc). It is an eight-valve SOHC design with an aluminium head and iron block. The engine has five main bearings, a cross flow head and a single down draught carburetor. Firing order is 1-3-4-2. The GSR versions used two twin-barrel Mikuni-built Solex carburetors for a total of 110 hp (82 kW) (SAE).

4G32 ECI engine in a Mitsubishi Mirage

A version with an early iteration of Mitsubishi's MCA lean-burn system (MCA-IIB), fulfilling the intermediate Japanese exhaust regulations for 1975, was called G32A. This was built for less than one year, as the new MCA engine arrived in November 1975. Those with the later, cleaner yet, "MCA-Jet" system were called G32B. Later, the G32B also came in a fuel injected, turbocharged model. For competition, a version of the 4G32 engine was made with a DOHC eight-valve cylinder head, and fitted with two twin-choke 40 mm (1.6 in) Solex sidedraft carburettors.

Bore x Stroke: 77 mm × 86 mm (3.03 in × 3.39 in)


Turbocharged version of the 4G32.


The 4G33 displaces 1.4 L (1,440 cc) from a 73 mm × 86 mm (2.87 in × 3.39 in) bore and stroke. There was also an MCA-Jet equipped G33B developed to fulfill the 1978 Japanese emissions regulations.



The 4G35 displaces 1.7 L (1,686 cc). It is an 8-valve SOHC design with an aluminium head and iron block. The engine has five main bearings. Power was 105–115 hp (78–86 kW) depending on which carburetor combo was used.

Bore x Stroke: 79 mm × 86 mm (3.11 in × 3.39 in)



The 4G36 displaces 1.2 L (1,239 cc). 73 mm × 74 mm (2.87 in × 2.91 in) bore and stroke.



The 8-valve SOHC 4G37 displaces 1.8 L (1,755 cc).

Bore x Stroke: 80.6 mm × 86 mm (3.17 in × 3.39 in)

Compression Ratio: 9.5:1


By other brands:


The 6G34, referred to by Mitsubishi as the Saturn 6, is a 12-valve SOHC straight-6 of 2.0 L (1,994 cc) displacement.

The 6G34 was used only in the Mitsubishi Debonair Executive from September 1970 to June 1976, and saw very limited production. Effectively, the design was that of the standard Saturn four-cylinder block with two additional cylinders grafted on to replace the KE64.


See alsoEdit


  1. ^ Büschi, Hans-Ulrich, ed. (5 March 1987). Automobil Revue 1987 (in German and French). 82. Berne, Switzerland: Hallwag AG. pp. 397–398. ISBN 3-444-00458-3.
  2. ^ 自動車ガイドブック: Japanese motor vehicles guide book 1973/1974 (in Japanese), 20, Japan: Japan Automobile Manufacturers Association, 30 October 1973, p. 298
  3. ^ Mastrostefano, Raffaele, ed. (1990). Quattroruote: Tutte le Auto del Mondo 1990 (in Italian). Milano: Editoriale Domus S.p.A. pp. 200–201.