HSV LS2 ‘Generation IV’ V8 engine (2004-08)

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Introduction

The LS2 was a 6.0-litre pushrod V8 petrol engine that was developed and manufactured by GM and offered in HSV models from 2004 to 2008. Based on the LS1 ‘Generation III’ engine, the LS2 ‘Generation IV’ engine was developed to support for cylinder deactivation (GM’s ‘Active Fuel Management’, or AFM) and variable valve timing technology. Specifically, AFM required the oil channels and galleries within the cylinder block to be redesigned for lubrication of the internals when the engine switched from running eight cylinders to four. For the HSV range, however, AFM was not available.

LS2 block

Like the LS1, the LS2 had a deep-skirt, aluminium cylinder block that was cast from 319-T5 aluminium and contained gray-iron cylinder bore liners that were centrifugally-cast. Furthermore, a die-cast valley cover and upper deck rails connected the cylinder banks for greater rigidity.

Although the 92.0 mm stroke was unchanged, the LS2 engine had 101.6 mm bores (compared to 99.0 mm for the LS1) which increased the engine’s capacity to 5967 cc. Like the LS6 (a higher output version of the LS1 developed for the Chevrolet Corvette), the LS2 engine had improved crankcase ventilation as the positive crankcase ventilation (PCV) valve was moved away from the rocker covers and into the block valley.

LS2 internals

Like the LS1, the LS2 engine had

• A nodular iron crankshaft that was held in place by five main bearings with six bolts per bearing cap (four vertical and two horizontal);
• Sintered and forged PF1159M steel connecting rods which had cracked’ big ends; and,
• Pistons made from cast eutectic aluminium.

For the LS2, however, changes included flat-top pistons with lower ring tension and floating gudgeon pins for quieter running (the latter previously introduced in the LS6). With the change to flat-top pistons, the compression ratio increased to 10.9:1.

LS2 cylinder head

Like the LS6 engine, the LS2 had 243′ aluminium cylinder heads, where 243 referred to the casting number. The 243 cylinder heads had raised intake ports and an unshrouded-valve combustion chamber for better air/fuel mixture formation.

LS2 camshaft

Like the LS1, the LS2 engine had a single, hollow camshaft that was produced from steel billet and had induction-hardened lobes. For the LS2, however,

• Camshaft lift was increased to benefit from the increased cylinder head flow;
• The camshaft sensor was repositioned from the rear of the block to the front (providing room for the new oil galleries); and,
• A stronger timing chain was introduced.

LS2 valvetrain

Similarly, the LS2 engine had two stainless steel valves per cylinder (one intake and one exhaust) that were actuated by cast steel, needle bearing roller rocker arms which had a ratio of 1.7:1. For the LS2 engine, changes included 50.8 mm intake valves, 39.4 mm exhaust valves and upgraded valve springs, though the valves continued to have hydraulic valve lifters.

LS2 lubrication and cooling

For the LS2 engine, the oil pan was redesigned with cast baffling to reduce mass and improve oil control; the bat wings’ of the LS1 oil pan were also omitted. The LS2 engine continued to use a gerotor oil pump, though a lighter water pump with improved sealing was fitted (as introduced in later versions of the LS1).

LS2 injection and ignition

Like its predecessor, the LS2 engine had electronic, sequential port fuel injection (SFI) and each cylinder had its own injector to meter fuel. Furthermore, each cylinder had its own ignition coil, coil driver assembly and short plug wire that connected to the spark plug. The LS2 engine, however, introduced more efficient ignition coils and, as per the LS6, long-life iridium spark plugs. Maximum engine speed for the LS2 engine was 6500 rpm.

The LS2 engine had electronic throttle control and a larger, 90 mm single-blade throttle body. For the LS2, the new powertrain control module (PCM) included electronic throttle control functions, such that a separate module was no longer required. The LS2 engine also had external knock sensors.

LS2 exhaust

The LS2 engine introduced a higher-flow and lighter exhaust manifold, as wall thickness was reduced from 4 mm to 3 mm. The catalytic converters – mounted closer to the exhaust manifold for quicker light-off and reduced cold-start emissions – were also more effective and less restrictive. As a result, the LS1’s auxiliary converters and air injection reaction system were omitted.

HSV LS2 upgrades

When first introduced in HSV’s Z-Series range, the LS2 engine produced peak power and torque of 297kW at 6000rpm and 530N at 4400rpm. For the E-Series range, outputs increased to 307kW at 6000rpm and 550Nm at 4400rpm due to a recalibrated engine control module (with a limp home’ mode) and new tubular extractors which fed into a twin-exhaust system with four outlet pipes.
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