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The Astron, along with Orion, Sirius and Saturn, was a series of straight-4 internal combustion engines first built by Mitsubishi Motors in 1972. Engine displacement ranged from 1.8 to 2.6 litres, making it one of the largest four cylinder engines of its time.

It employed a hemispherical cylinder head, chain-driven single overhead camshaft (SOHC) and eight valves (two per cylinder). United States passenger car versions had a small secondary intake valve referred to as the "Jet Valve". This valve induced swirl in the intake charge, enabling the use of leaner fuel/air mixtures for lower emissions. It was designed as a cartridge containing the valve spring and seat which simply screwed into a threaded hole in the head, similar to a spark plug but inside the cam cover. The rocker arms for the intake valve were widened on the valve end to accommodate the cartridge, which was equipped with a very soft valve spring in order to avoid wear on the camshaft intake lobe. Modifications to the head were thereby reduced as the Jet Valve negated the necessity for a three valve per cylinder design.

In 1975, the Astron 80 introduced a system dubbed "Silent Shaft"; the first use of twin balance shafts in a modern engine. It followed the designs of Frederick Lanchester, whose original patents Mitsubishi had obtained, and proved influential as later engines from Fiat / Lancia, Saab and Porsche all licenced this technology.[1]

The 4D5x was a range of four cylinder diesel engines, part of the "Astron" family and introduced in 1980 in the then new 5th generation Galant. The first turbodiesel to be offered in a Japanese passenger car, it later proved popular in the emerging SUV and minivan markets where Mitsubishi was highly successful, until superseded by the 4M4x range in 1993. However, production of the 4D5x continued throughout the 1990s as a lower-cost option than the more modern powerplants.

Contents 1 4G52 2 4G54 2.1 ECI-Multi 2.2 Carburetor 3 4G55 4 4D55 4.1 Turbo 5 4D56 5.1 Diesel 5.2 Turbo 5.3 Intercooled turbo 5.4 Common rail intercooled turbo 6 See also

The 4G52 displaces 2.0 L (1995 cc).

Applications:

• 1979-1989 Dodge Ram 50
• 1973-1987 Mitsubishi Sigma
• 1986-present Mitsubishi L300

The SOHC 8-valve 4G54 (also known as the G54B) displaces 2.6 L (2555 cc), Bore x stroke is 91.1 mm x 98.0 mm. Some had heads with additional jet valves to improve emissions. It was designed for longitudinal use in rear-wheel drive and all-wheel drive vehicles. It was equipped with a Hitachi 2-barrel carburetor with a vacuum-operated progressive secondary, except for the turbocharged version and a version used in Australian Mitsubishi Magnas, which were fuel-injected. This engine was also used on Chrysler's front-wheel drive K-cars and their derivatives from 1981 until 1987, when it was replaced by Chrysler's 2.5 L engine. This engine was commonly paired with Chrysler's A470 3-speed automatic transmission on Chrysler vehicles.

Specifications:

Multi-Point Fuel Injection

• 98 kw at 4750 rpm (91 RON)
• 102 kw at 4750 rpm (95 RON)
• 212 nm at 3750 rpm (91 RON)
• 220 nm at 4000 rpm (95 RON)
• Compression ratio: 9.2:1

Single two-Venturi downdraught carburetor

• 85 kw at 5000 rpm (91 RON)
• 198 nm at 3000 rpm (91 RON)
• Compression ratio: 8.8:1

Applications:

• 1978-1980 Plymouth Fire Arrow
• 1978-1983 Dodge Challenger/Mitsubishi Sapporo/Plymouth Sapporo
• 1978-1987 Mitsubishi Sigma
• 1979-1989 Dodge Ram 50
• 1981-1985 Dodge Aries/Plymouth Reliant
• 1982-1985 Chrysler LeBaron
• 1982-1985 Chrysler Town and Country
• 1987-1991 Isuzu Pick Up TF (Japanese Built)
• 1982-1991 Mitsubishi Pajero
• 1982-1983 Dodge 400
• 1983-1984 Chrysler E-Class
• 1983-1985 Chrysler New Yorker/Dodge 600
• 1984-1987 Dodge Caravan/Plymouth Voyager
• 1982-1990 Mitsubishi Starion (turbocharged and fuel injected)
• 1984-1986 Dodge Conquest/Plymouth Conquest
• 1985 Plymouth Caravelle
• 1985-1996 Mitsubishi Magna (early carbureted, later EFI)
• 1986-1989 Mazda B2600 (with a Mazda 12-valve head)
• 1987-1989 Chrysler Conquest

The 4G55 displaces 2.3 L (2346 cc).

Displacement - 2346 cc
Bore - unknown
Stroke - unknown
Fuel type - Diesel

• Power - 62 kW (84 PS) at 4000 rpm
• Torque - 175 N·m (129 ft·lbf) at 2000 rpm
• Engine type - Inline 4 cylinder SOHC
• Fuel system - unknown
• Compression ratio - unknown

Displacement - 2476 cc
Bore - 91.1 mm
Stroke - 95.0 mm
Fuel type - Diesel

• Power - 51 kW (70 PS) at 4200 rpm
• Torque - 143 N·m (105 ft·lbf) at 2500 rpm
• Engine type - Inline 4 cylinder SOHC
• Fuel system - Distribution type jet pump
• Compression ratio - 21:1

• Power - 63 kW (85 PS) at 4000 rpm
• Torque - 196 N·m (145 ft·lbf) at 2000 rpm
• Engine type - Inline 4 cylinder SOHC
• Fuel system - Distribution type jet pump
• Compression ratio - 21:1

• Power - 77 kW (105 PS) at 4000 rpm
• Torque - 240 N·m (177 ft·lbf) at 2000 rpm
• Engine type - Inline 4 cylinder SOHC
• Fuel system - Distributor type injection pump
• Compression ratio - 21:1

• Power - 99 kW (134 PS) at 4000 rpm
• Torque - 314 N·m (232 ft·lbf) at 2000 rpm
• Engine type - Inline 4 cylinder DOHC
• Fuel system - Common rail direct injection
• Compression ratio - 17:1

List of Mitsubishi engines

MITSUBISHI MOTORS v • d • e

Engines, platforms & technologies: 2G | 3B | 3G | 3A9x | 4A3x | 4A9x | 4B | 4D5x | 4G1x | 4G3x | 4G4x | 4G5x | 4G6x | 4G9x | 4M | 6A | 6B | 6G | 8A | KE Astron | Cyclone V6 | GEMA | Neptune | Orion | Saturn | Sirius | Vulcan

GS platform | PS platform | Z platform

ACD | Active-Trac | AWC | AYC | GDI | INVECS | MATT | MIEV | MIVEC | MultiMode ABS | Modulated Displacement | RISE | Silent Shaft | Sport ABS | Super Select | Vertical Vortex