Audi BCY Specifications
| Engine Model: Audi BCY |
| Engine Type: 4-cycle 8-cylinder DOHC 40-valve twin-turbocharged liquid-cooled gasoline |
| Total Displacement: 254.6 cu.in (4.17 L) |
| Rated Engine Power: 444 Hp (331 kW) at 6400 rpm |
| Fuel System Type: Sequential multi-port fuel injection (MPFI) |
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The Audi BCY is the engine code for the
4.2-liter, twin-turbocharged V8 powerplant developed exclusively for the
Audi RS 6 (C5). This engine represents a landmark achievement for Audi,
being the first twin-turbo V8 from the brand and one of the most
powerful production sedan engines of its era. Based on Audi's
all-aluminum 40-valve V8 architecture, it incorporates two KKK
turbochargers, air-to-air intercoolers, a reinforced block, and a
sophisticated Bosch Motronic engine management system.
The BCY delivers immense, linear power and torque, defining the
character of the high-performance RS 6 Avant and sedan. Its engineering
prioritizes robust performance with a focus on durability under high
stress, utilizing forged connecting rods and a specially reinforced
crankcase. While complex and demanding in terms of maintenance and fuel
consumption, the BCY engine established Audi as a serious contender in
the ultra-high-performance segment and remains a highly respected and
potent powerplant.
Engine Type: 90-degree V8, liquid-cooled, twin-turbocharged and
intercooled, multi-point fuel injection (MPI). Displacement: 4172 cc
(4.172 L) / 254.6 cu.in.
Bore x Stroke: 84.5 mm x 93.0 mm / 3.33 in x 3.66 in.
Compression Ratio: 9.0:1. Firing Order: 1-5-4-8-6-3-7-2.
Direction of Rotation: Clockwise (viewed from the front/flywheel end).
Maximum Power Output: 331 kW (450 PS) at 6400 rpm. Imperial: 444 Hp at
6400 rpm.
Maximum Torque Output: 560 Nm at 1950-5600 rpm. Imperial: 413 lb-ft
(lb-ft) at 1950-5600 rpm.
Fuel Requirement: Premium unleaded gasoline, 98 RON (93 AKI) mandatory
for stated performance.
Emission Standards Compliance: Euro 3.
Material: Aluminum alloy with cast-in silicon-aluminum cylinder liners
(Alusil technology). The block is a reinforced, closed-deck design
derived from the naturally aspirated 4.2 V8 but with added material in
critical areas to withstand turbocharging pressures.
Construction: 90-degree V8 configuration with a split crankcase
(bedplate). The crankshaft is supported by five main bearings. The main
bearing caps are cross-bolted for maximum rigidity.
Crankshaft: Forged steel crankshaft. Main bearing journal diameter: 70.0
mm / 2.756 in. Crankpin journal diameter: 58.0 mm / 2.283 in.
Pistons: Cast aluminum alloy pistons with a dished crown design for the
9.0:1 compression ratio. All pistons are oil-jet cooled. Connecting
Rods: Forged steel connecting rods, a critical upgrade for handling
increased cylinder pressure.
Material: Aluminum alloy.
Head Construction: Dual overhead camshafts (DOHC) per bank, 40-valve
design (5 valves per cylinder: 3 intake, 2 exhaust). The camshafts are
driven by dual timing chains (one per bank).
Valve Arrangement: Valves are arranged in a compact pent-roof combustion
chamber. They are actuated via bucket tappets with shims for manual
valve clearance adjustment. This is an interference engine. Variable
Valve Timing: The intake camshafts on each bank feature vane-type
adjusters (VVT) for variable valve timing. Variable Intake Manifold: A
two-stage intake manifold with switchable flap valves optimizes torque
delivery. Valve Diameters: Intake (small): 26.0 mm / 1.024 in. Intake
(large): 29.5 mm / 1.161 in. Exhaust: 30.5 mm / 1.201 in.
Injection Type: Sequential multi-port fuel injection (MPI).
Engine Management: Bosch Motronic ME7.1.1 engine control unit. This
advanced system manages fuel injection, ignition timing, boost pressure,
and variable valve timing for both banks.
Fuel Delivery: Dual electric in-tank fuel pumps supply high volume to
the fuel rails.
Fuel Rail and Injectors: Eight high-flow solenoid-operated fuel
injectors.
Turbochargers: Two parallel KKK K04 turbochargers, one for each cylinder
bank. Each turbo features an integrated wastegate. Intercoolers: Two
separate air-to-air intercoolers, one mounted in each front fender
liner. Throttle Body: Single, electronically controlled (drive-by-wire)
throttle body.
Type: Pressure-fed, full-flow filtration with a gear-type oil pump. The
system includes a large oil cooler.
Oil Pump: Gear-type pump, driven by the crankshaft.
Oil Filter: Cartridge-type, mounted on the front of the engine block.
Oil Cooler: A dedicated engine oil cooler (oil-to-coolant) is integrated
into the cooling system.
Oil Capacity (including filter): 9.0 L / 9.5 US qt.
Recommended Oil Grade: Full synthetic engine oil meeting VW oil standard
503 01 (Audi Longlife) or 502 00. Viscosity: 0W-40 or 5W-40. Operating
Oil Pressure: 2.0 bar at hot idle, 4.0 - 5.0 bar at 2000 rpm. Imperial:
29 psi (idle), 58 - 73 psi (2000 rpm).
Type: Pressurized, dual-circuit system with a main radiator and separate
circuits for the intercoolers and engine oil cooler. An auxiliary
electric pump provides after-run cooling.
Water Pump: Centrifugal pump, driven by the accessory serpentine belt.
Thermostat: Map-controlled thermostat for precise temperature
management.
Coolant Capacity: 12.0 L / 12.7 US qt (entire system).
Coolant Type: VW G12 (pink) or G12++ ethylene glycol-based antifreeze.
Electrical System: 12-volt negative ground. 190-amp alternator.
Ignition System: Distributorless ignition system with eight individual
coil packs (coil-on-plug), controlled by the Bosch Motronic ECU.
Engine Management: Bosch Motronic ME7.1.1 as stated. The system uses two
hot-film mass air flow (MAF) sensors (one per turbo inlet) and four
knock sensors (two per bank).
Exhaust System: Dual stainless steel exhaust manifolds feeding the
turbochargers. The system includes primary catalytic converters and
secondary silencers.
Crankcase Ventilation: A complex, closed Positive Crankcase Ventilation
(PCV) system with an oil separator.
Overall Length: 750 mm / 29.5 in.
Overall Width: 800 mm / 31.5 in.
Overall Height: 700 mm / 27.6 in.
Dry Weight: 220 kg / 485 lbs.
Engine Oil Change Interval: Strictly every 10,000 km or 12 months.
Severe service demands 5,000 km or 6-month intervals. Imperial: 6,200
miles / 3,100 miles. Oil quality is critical. Oil Filter Change: Every
oil change. Fuel Filter Change: Every 60,000 km (37,300 miles). Air
Filter Change: Every 30,000 km (18,600 miles) or as inspected; two
filters are required.
Timing Chain Service: The timing chains, tensioners, and guides are
considered lifetime components but require inspection for wear and
stretch at high mileage (beyond 150,000 km / 93,000 miles). Service is
complex and costly. Spark Plug Replacement: Specified platinum or
iridium spark plugs require replacement every 60,000 km (37,300 miles).
Coolant Replacement: Every 2 years. Valve Clearance Adjustment: Check
and adjust (via shim replacement) every 105,000 km (65,000 miles).
Clearance (cold): Intake: 0.15-0.25 mm (0.006-0.010 in). Exhaust:
0.25-0.35 mm (0.010-0.014 in). Turbocharger System: Regular inspection
of intercooler pipes, vacuum lines for the wastegate actuators, and
turbo seals is essential.
Cylinder Head Bolts: Torque-to-yield (TTY) bolts. Tighten in the
specified sequence: Step 1: 60 Nm (44 lb-ft). Step 2: +90° turn. Step 3:
Final +90° turn. These bolts are single-use.
Main Bearing Cap Bolts (Bedplate): 80 Nm (59 lb-ft) + 90° turn.
Connecting Rod Cap Bolts: 30 Nm (22 lb-ft) + 90° turn (replace bolts).
Spark Plugs: 30 Nm (22 lb-ft).
Oil Drain Plug: 30 Nm (22 lb-ft).
Crankshaft Pulley Bolt: 350 Nm (258 lb-ft) + 90° turn.
Turbocharger to Exhaust Manifold Nuts: 35 Nm (26 lb-ft).
Wheel Bolts: 120 Nm (89 lb-ft).
The Audi BCY engine had one exclusive application: Audi RS 6 (C5,
2002-2004): This engine powered both the RS 6 sedan (Typ 4B) and the RS
6 Avant (Typ 4B). It was the core of Audi's flagship performance model
during this period, competing directly with the contemporary BMW M5 and
Mercedes-Benz E55 AMG.
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