to 42 degrees adjustment, each controlled via information from Hall sensors, Audi "RS" 'red' plastic cam covers on RS 4, 'anthracite' plastic on R8 aspiration two single-entry air filters each with hot-film air mass flow meters (Q7), or triple-entry single air filter with single hot-film air mass meter (RS 4), or double-entry dual-element single air filter with two hot-film air mass flow meters (R8); single (Q7 & RS 4) or twin (R8) cast alloy throttle body electronically controlled Bosch E-Gas throttle valves (Bosch diameter on Q7, Pierburg diameter on RS4), two-stage four-piece gravity die-cast (Q7) (sand-cast on RS 4/R8) magnesium-aluminium alloy variable length intake manifold with electronically map-controlled silicon tipped tract-length flaps along with tumble flaps inducing a swirling movement in the drawn air (RS 4 & R8 do not use a variable tract-length intake manifold) fuel system fully demand-controlled, (Q7 returnless, RS 4 return to tank); fuel tank–mounted low-pressure fuel pump; Fuel Stratified Injection (FSI): two inlet camshaft double-cam driven single-piston high-pressure injection pumps maintaining a pressure between in the two stainless steel common rail fuel distributor rails, eight combustion chamber sited direct injection solenoid-controlled 65 volt single-hole sequential fuel injectors with integrated swirl plates; 98 RON/ROZ (93 AKI) EuroSuperPlus (premium) unleaded recommended for maximum performance and fuel economy (95 RON (91 AKI) may be used, but will reduce performance and worsen fuel economy) ignition system & engine management mapped direct ignition with centrally mounted longlife spark plugs and eight individual direct-acting single spark coils; Bosch Motronic MED 9.1.1 electronic engine control unit (ECU) (two MED 9.1 ECUs in the RS 4 and R8, working on the 'master and slave' concept due to the high revving nature of the engine), four knock sensors, EU4 emissions standard, map-controlled coolant thermostat (Q7 only), additional electric after-run coolant pump with two additional side-mounted radiators (RS 4/R8), water-cooled alternator, two map-controlled radiator fans exhaust system vacuum-controlled secondary air injection to assist cold start operation; air-gap insulated exhaust manifold per cylinder bank (Q7), or 4-into-2-into-1 fan-branch exhaust manifold per cylinder bank to minimise reverse pulsation of expelled exhaust gases (RS 4), or fan branch manifold with integrated catalytic converter per cylinder bank; two close-coupled and two main underfloor catalytic converters – ceramic on Q7, high-flow metallic on RS 4, or main catalytic converter integrated into transverse main rear silencer with quad outlets; four heated oxygen (lambda) sensors (broadband upstream, nonlinear downstream) monitoring pre- and