2g Astron II

Second Generation Astron II combustion chambers

Rocker gear on the Second Generation Astron II

Second Generation Astron II dished pistons

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 Type In line 4 cylinder overhead cam with counter balance shafts. Transversely mounted Displacement 2555cc (2.6 litres) Bore 91.1mm Stroke 98mm Maximum oversize 1.00mm Compression Ratio 9.2:1 Firing Order 1,3,4,2 Power Output (EFI) 98 kW @ 4750 rpm (103kW when running PULP), 212 Nm @ 3750 rpm HEAD SPECIFICATIONS Type Alluminum Alloy with hemispherical combustion chambers and crossflow design Inlet Valve Diameter 46.00mm Exhaust Valve Diameter 38.00mm Valve Face Angle 45 º Valve Clearance Maintained by hydraulic lash adjusters CAMSHAFT SPECIFICATIONS Inlet Opens 25º BTDC Inlet Closes 61º ABDC Inlet Duration 266º Exhaust Opens 66º BBDC Exhaust Closes 20º ABDC Exhaust Duration 266º Overlap 45º Inlet Cam Lobe Height 42.50mm Exhaust Cam Lobe Height 42.56mm Nominal Cam Lift 10.50mm

MITSUBISHI PETROL ENGINES 3 cylinder 3A9x 3A90 3A91 3A92 4 cylinder Neptune 4G41 4G42 Orion 4G11 4G12 4G13 4G15 4G17 4G18 4G19 G4ED Sirius 4G61 4G62 4G63 4G64 4G67 4G69 Astron 4G51 4G52 4G53 4G54 Astron II Original Revised Saturn 4G30 4G31 4G32 4G33 4G37 4G9x 4G91 4G92 4G93 4G94 4A9x 4A90 4A91 4A92 4B1x 4B10 4B11 4B11T 4B12 Inline 6 Saturn 6 6G34 V6 6G7x 6G71 6G72 SOHC 12v 6G72 SOHC 24v 6G72 DOHC Early 6G74 Late 6G74 Ralliart 6G74 6G75 6A1x 6A10 6A11 6A12 6A13 6B3x 6B31 V8 8A80 8A80