. The B6 S4 saloon and Avant variants ceased factory production in December 2004, with the Cabriolet ending twelve months later at December 2005. B6 powertrain Replacing the 2.7-litre 'biturbo' V6 engine of the previous generation B5 S4, the new B6 S4 powertrain gained an all-aluminium alloy 4.2-litre, 40 valve (five valves per cylinder) V8 engine (parts code prefix: 079.C, identification code: BBK), with chain-driven double overhead camshafts, roller-finger rocker arm cam followers, and included variable inlet camshaft timing. It also used a strengthened alloy crankshaft bedplate for the five main bearings, and a two-part baffled oil sump, and a light-alloy variable intake manifold (VIM), containing the fractionally sequentially actuated fuel injectors. This petrol engine, based on the unit from the Audi A8, displaces , and it produces a motive power output of at 7,000 rpm, and generates torque of at 3,500 rpm, making it more powerful than the RS2 Avant, and nearly as powerful as the B5 RS4. Engine management was by way of a Bosch Motronic ME 7.1.1 electronic engine control unit (ECU), using a Bosch 'E-Gas' drive by wire electronic throttle, and powering eight individual spark coils with longlife quad-electrode Bosch spark plugs. Ignition timing is a mapped direct ignition, with cylinder-selective knock control with the aid of four knock sensors. The exhaust system includes vacuum-operated valves in the twin rear silencers (mufflers), finished with chrome plated tail-pipes. Like its predecessors, the B6 S4 was standard with a Getrag six-speed (M6S) manual transmission (parts code prefix: 0A3, identification codes: FVD, HEP) (gear ratios - 1st: 3.667, 2nd: 2.050, 3rd: 1.462, 4th: 1.133, 5th: 0.919, 6th: 0.778), with a single plate dry clutch, and Torsen T-2 quattro permanent four-wheel drive system. Final drive (parts code prefix: 01R, identification code: EXZ) ratios are 3.889, giving a top gear road speed to engine revs ratio of per 1000 rpm. From July 2003, the ZF 6HP19 tiptronic automatic transmission (parts code prefix: 09L, identification codes: GUR, HHU) (ratios - 1st: 4.171, 2nd: 2.340, 3rd: 1.521, 4th: 1.143, 5th: 0.867, 6th: 0.691, with a final drive (identification code: GDF) ratio of 3.539) was included as an option. An unusual sight in the engine compartment was the addition of water cooling for the 190 amp alternator, along with two additional thermostatically-controlled side-mounted radiators. B6 steering, brakes, wheels & tyres The B6 S4 came equipped with electronically controlled, variable assisted 'servotronic' rack and pinion