Design
The S68 has the same piston stroke of 88.3 mm (3.48 in) and displacement as its N63 predecessor, but the compression ratio of 10.5:1 corresponds to the higher compressed predecessor variants. [6] It has one turbocharger per cylinder bank and both turbochargers are placed in the middle of the cylinder banks in a hot-vee design taken from the previous S63 variant; there is only one exhaust manifold. The S68 is the only current production V8 engine offered with a cross-pattern exhaust manifold for improved turbo charger pressure by combining exhaust pulses which comes at an expense of sound alternation, making the sound closer to a 180 degree configuration V8. The engine oil is cooled by an external cooler, and a newly developed oil pump is used for the oil circuit. The engine is now only offered as a 48-volt mild hybrid powerplant mild hybrid system, it has a 9 kW (12 hp) electric motor with a torque of 200 N⋅m (150 lbf⋅ft); unlike the previous mild hybrid systems from BMW, this is installed within the transmission. [1] The electric motor is also used for hot starts, while cold starts are performed by a standard 12 volt starter similar to most other engines. The batttery required for this has a 90 Ah capacity. The 48-volt battery found in the X7 M60i, XM, and the 760i models has a capacity of 20 Ah. [6] [7] The variable camshaft control (VANOS) is now electrical and no longer hydraulic. [7] The S68 currently meets the Euro 6d emissions standard, [1] [6] but should also be able to achieve the stricter Euro 7 standard, which is planned for 2025. [8] [7]
The electric motor in the S68 has a torque of 200 N⋅m (150 lbf⋅ft). [2] [3] Maximum revs are 7200 rpm. [9]
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