Mitsubishi Neptune engine

The Mitsubishi Neptune or 4G4 engine is a series of iron-block OHV inline-four engines built by Mitsubishi Motors from June 1971 to 1981.[1] This was to be Mitsubishi's last OHV engine. The inability to clear new passenger car emissions rules for 1978 meant that the Neptunes were replaced by the 4G1 Orion. The Neptune continued to be built until 1979 for commercial vehicles, which suffered less restrictive environmental regulations and until about 1981 for other applications. Around 520,000 Neptune engines were built.[1]

Neptune engine
Overview
ManufacturerMitsubishi Motors
Also called4G4
Production1971–1981
Layout
ConfigurationInline-4
Displacement1.2–1.4 L (1,188–1,378 cc)
Cylinder bore71 mm (2.8 in)
76.5 mm (3.01 in)
Piston stroke75 mm (2.95 in)
Cylinder block materialCast iron
ValvetrainOHV 2 valves x cyl.
Compression ratio9.0:1
Combustion
Fuel typeGasoline
Cooling systemWater-cooled
Output
Power output70–87 PS (51–64 kW; 69–86 hp)
Torque output9.7–11.7 kg⋅m (95–115 N⋅m; 70–85 lb⋅ft)
Chronology
PredecessorKE engine
Successor4G1 Orion

4G41

Displacement1.4 L (1,378 cc)
Bore x Stroke76.5 mm × 75 mm (3.01 in × 2.95 in)
Power86 PS (63 kW; 85 hp) at 6,000 rpm (single carb)

95 PS (70 kW; 94 hp) at 6,300 rpm (Galant FTO, twin carb)
28 PS (21 kW; 28 hp) at 2,700 rpm in a 1972 FG15 forklift[2]

Torque11.7 kg⋅m (115 N⋅m; 85 lb⋅ft) at 4,000 rpm (single carb)

8.6 kg⋅m (84 N⋅m; 62 lb⋅ft) at 2,000 rpm in a 1972 FG15 forklift[2]

Applications

4G42

Displacement1.2 L (1,188 cc)[4]
Bore x Stroke71 mm × 75 mm (2.80 in × 2.95 in)
Power70 PS (51 kW; 69 hp) SAE at 6,000 rpm
Torque9.7 kg⋅m (95 N⋅m; 70 lb⋅ft) at 4,000 rpm

Applications

See also

References

  1. "1971: 4G4型(ネプチューン)エンジンの生産を開始" [1971: Started production of 4G4 (Neptune) engine]. 会社の歴史 _ 三菱自動車の歴史(沿革) [Company History: History of Mitsubishi Motors] (in Japanese). Mitsubishi Motors. Archived from the original on 2022-08-07.
  2. 自動車ガイドブック: Japanese motor vehicles guide book 1972—73 (in Japanese), vol. 19, Japan: Japan Automobile Manufacturers Association, 1972-10-23, p. 294
  3. Kazuhiko. 初代デリカ(T系) [First Delica (T-series)]. Delica History (in Japanese). Archived from the original on 21 July 2011.
  4. Car Graphic: Car Archives Vol. 5, '70s Japanese Cars. Tokyo: Nigensha. 2007. p. 77. ISBN 978-4-544-09175-5.
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