Astron II
| Astron II | |
|---|---|
 Astron II in a first generation Magna | |
| Overview | |
| Manufacturer | Mitsubishi Motors Australia Limited |
| Also called | 4G54, 4G54B, G54B |
| Production | 1985 - 1996 |
| Layout | |
| Configuration | In-line 4 |
| Displacement | 2555cc |
| Cylinder block alloy | Cast Iron |
| Cylinder head alloy | Aluminum Alloy |
| Valvetrain | SOHC |
| Chronology | |
| Predecessor | Astron |
| Successor | Sirius |
The Astron II was an improved version of the original Astron and debuted in the mid 1980s. It was available only in 2.6 Litre form.
The Astron II's main difference over its predecessor were in the cylinder head with hemispherical style combustion chambers, larger exhaust and inlet valves and hydraulic lash adjusters. The pistons were flat topped with compression rising to 8.8:1 (up from 8.2:1) to produce 83 kW at 5200 rpm and 200 Nm at 2400 rpm (up from 76kW at 4800rpm and 192 Nm at 2400 rpm) in carburetted form.
The 2.6 Litre engine was praised for being powerful, economical and refined.
Original Astron II
The Original Astron II was fitted to the all First Generation Magnas (TM-TP), carburetted Second Generation Magnas (TR-TS), the GN Sigma, Triton XX and Pajero XX. These typically had the numbers M1 through M5 cast into the head and V5xx engine numbers.
Technical Specifications
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Revised Astron II
The second generation Astron II was fitted to fuel-injected TR and TS models.
The revised Astron II included "kidney shaped" combustion chambers in the cylinder head, roller rockers, dished top pistons and the self-adjusting balance shaft chain adjusting mechanism fitted to late model Astron IIs.
The quickest way to identify the second generation Astron II from the original is to look for a knock sensor under the injection plant. First generation Astron IIs do not even have a hole for it. Other methods are by it's engine number (prefixed by W531, W532) or by the casting number on the head. Second generation heads are marked "M9".
As a result of these modifications the compression ratio raised to 9.2:1 and power rose to 98kW @ 4750 rpm (103 kW if ran on premium unleaded thanks to the knock sensor included as part of the engine management system). Torque also rose to 212Nm @ 3750 rpm.
Technical Specifications
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