V8 Engines: LS2 vs LS1

By Chris Shumack - 5/Apr/2007

Melbourne, Australia — If you didn’t know the difference between an LS1 and LS2 engine apart from the badge and the GM fans lust for them, you’d be on the right track if you guessed that the LS2 it simply a revised Generation III block with Generation III heads. 

While in most parts this is correct, and the revisions are small, they are numerous and make an amazing difference - improving power and torque, while improving fuel economy.

One of the main driving forces behind the LS2 design is fuel economy. A newly developed ‘Displacement on Demand Technology’ (DOD) is available for all Generation IV LS2 engines in the US, with it;s Australian debut still pending. 

While it is not available just yet here in Australia, the displacement on demand is worked as simply a matter of programming in the ECM, and even though it isn't burnt into the memory of our Aussie versions, I’ve mentioned it because it’s operation requires intricate modifications to the LS1 engine block to function, and hence the LS2's reason for being.

The way it works is similar to other engine technologies as seen in Jeep's ‘Hemi’ engines. It shuts off  4 out of 8 cylinders when the ECM determines load is small enough on the engine for it to operate on half it’s normal power without damage or engine stall, and when throttle or engine load increases, the ECM will switch back to the full power of it’s 8 cylinders.

Support for the new technology has required oil channels and galleries throughout the block to be redesigned for correct lubrication of the internals switching between normal and DOD modes. Other revisions to the bottom end is a new oil pan – the design coming from the GM muscle camp Corvette, who in their C6 reshaped the pan itself and channels inside the pan to avoid oil starvation while lateral G’s are present, and keeps oil being distributed through the running engine during hard cornering.

As I mentioned before the heads are slightly modified LS1 Generation III heads – LS6 heads that is. They are modified by raising the intake ports and using unshrouded valves, which are driven by a high lift LS6 camshaft which in turn is driven by a strengthened timing chain. 

The use of these heads enabled the increase of the bore size from 3.9-inches to 4-inches and increased compression – all combining to give the impressive figures that the LS2 boasts in the SS V Commodore 270kW and 530Nm. In fact, it has such high compression when compared to both it’s formers: the LS1 at 10.1:1, and LS6 at 10.5:1, it might leave a bit of a question mark next to whether or not forced induction has much headroom where the manifold pressures are concerned. 

Forced induction fans need not worry too much about this, as the manifold has been upgraded to the LS6 manifold which have larger valves (2-inch exhaust, 1.55-inch intake) to aid with moving that fuel in, and the exhaust away more efficiently. The exhaust manifolds are bored out to give a wall thickness of 3mm instead of 4mm for extra flow and the pistons also have been updated to include a flatter top and lower tension piston rings for low friction and full floating wrist pins. This is rumoured to reduce ‘piston-slap’ noise but is most probably more geared towards the abovementioned DOD technology.

Throttle control has been moved from the cable driven system to a ‘drive-by-wire’ system that now takes input from the loud pedal and then controls the Electronic Throttle Control. This is advantageous because now the ECM can control the throttle directly via the ETC and hence there is no need for a cruise control throttle relaxer or an accelerator cable.

Smaller revisions include knock engine sensors that are now at the front of the engine rather than in the valley, and the PCV Valve is now in the valley instead of the rocker covers also. The water pump has been redesigned for weight and greater leakproofing and the ignition coil packs are of higher efficiency.