cylinder heads & valvetrain cast aluminium alloy, partition-plate horizontally divided intake ports producing a tumble effect (larger cross-section on RS4/R8); four valves per cylinder: chrome-plated solid-stem (hollow-stem on RS4/R8) intake valves, and chrome-plated sodium-filled hollow-stem exhaust valves, both with 11 mm valve lift (longer valve lift on RS4/R8), 32 valves total; lightweight low-friction roller finger cam followers (uprated with peened rollers on RS4/R8) with automatic hydraulic valve clearance compensation, double overhead camshafts (each a hollow tube composite) on each cylinder bank, driven from the flywheel side via a two-stage chain drive using three 3/8" simplex roller chains (sleeve-type on RS4/R8), valve opening (in crank angle degrees) 200 intake (230 for RS4/R8) and 210 e exhaust (230 for RS4/R8); valve overlap facilitates integral exhaust gas recirculation; continuous hydraulic vane-adjustable variable valve timing for intake and exhaust camshafts with up to 42 degrees adjustment, each controlled via information from Hall sensors, Audi "RS" 'red' plastic cam covers on RS4, 'anthracite' plastic on R8