journals with cross bolted caps, different connecting rods, and different pistons. The blocks were machined differently, to accept extra sensors for the Gems and Bosch (Thor) injection system and to allow the extra stroke of the 4.6 crankshaft. For the 2003 and 2004 model year, Discovery II they changed to the 4.6-litre V8 (though the 4.0 continued as the only V8 option offered in the UK). ACE (Active Cornering Enhancement, an electronically controlled hydraulic anti-roll bar system) was fitted to some versions, which reduced cornering roll. A pair of accelerometers are used to detect the angle of body lean and to instruct the ACE computer to counteract these movements by applying pressure to the vehicle's torsion bars via actuators which are hydraulically controlled. On the Land Rover Discovery, the ACE system can counteract up 1 g of lateral acceleration in less than a tenth of a second, thus helping the vehicle become more stable and responsive during hard cornering. Self-levelling air springs were fitted to some models and European type-approval for seven-seat vehicles was only given to air-sprung examples. The locking center differential was still fitted although the actual mechanism linkage was not on the early series II production, as Land Rover believed that the traction control system [TCS] and newly developed Hill Descent Control system [HDC] would render it redundant. It was fully reinstated (with the linkage) on the facelift model in 2002, as a cost option (although standard equipment on high spec vehicles). Whilst the traction control system worked very effectively, it did not offer the same level of control and smooth operation as the vehicles fitted with the differential lock. Customer demand saw the diff lock controls fully reinstated on UK and Irish models, and aftermarket kits are offered by several vendors for those vehicles which were produced with the lock, but not the linkage. For 2003 and 2004, the US version was available in three trim levels: S, SE, and HSE. Those with the seven-seat option were known as the S7, SE7, and HSE7. The "facelift" models are easily identified by new "pocketed" headlamps (which matched the Range Rover and facelifted Freelander models) as well as redesigned turn and brake lamps on the rear of the vehicle. The indicators were moved from the bumper to the high side fixtures. The earlier Series II models could in turn be easily distinguished from the original Discovery by the