2g 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.