BMW S85

BMW S85 engine
Overview
Manufacturer	BMW Bayerische Motoren Werke
Production	2005–2010
Combustion chamber
Configuration	90° V10, odd-firing
Cylinder bore	92 mm
Piston stroke	75.2 mm
Cylinder block alloy	Aluminum–silicon alloy
Cylinder head alloy	Aluminum alloy
Valvetrain	DOHC, double-VANOS
Compression ratio	12.0:1
Combustion
Fuel system	Fuel injection
Management	Siemens MS S65 ECU
Fuel type	Gasoline
Cooling system	Water-cooled
Output
Power output	373 kilowatts (500 hp)
Torque output	520 N·m (384 lb·ft)
Dimensions
Dry weight	240 kg (529 lb)
Chronology
Predecessor	S62
Successor	S63

The BMW S85B50 is a DOHC V10 piston engine which replaced the S62 and was produced from 2005-2010. Used in the E60 M5 sedan, E61 M5 touring and E63/64 M6 coupé, it was inspired by BMW's previous Formula 1 involvement.^[1]

Nomenclature

As the S85 was BMW's first V10 engine, it was given a new series in the nomenclature. While V8 engines are designated by "60s" and V12 engines labeled as "70s", the S85 was badged with an "80" despite it having fewer cylinders than the "70"-series engines.

The S85 spawned a related S65 V8 engine for the 2008 BMW M3. Although the "65" designation is apparently out of order compared to the other V8 engines (which follow "62" and "63" sequentially), the S65 was badged such since its design is largely derived from the S85 minus two cylinders, and not related to BMW's other V8s.

Unlike other BMW engines, there are no mass market "M" or "N" versions of the S85 and S65 and nor are there any shared parts, as these engines are used exclusively in BMW M performance vehicles.^[2]

Technology

The S85B50 is a high-revving engine designed to utilize power from a wide rev band. Having a redline of 8250 rpm, it achieves over 100 bhp (70 kW)/litre. The S85 features a very high compression ratio of 12.0:1, exceeding the previous S54's ratio of 11.5:1.

It produces over 100 hp more than the previous E39 4.9liter V8, whilst weighing only 2.2 pounds more. The S85 utilizes both individual throttle bodies and Double VANOS (BMW's infinitely variable timing for intake and exhaust cams.^[3]

• 5.0 Litre V10 engine, 90 degree bank angle, 507 hp (378 kW) @ 7750rpm/520 N·m (384 lb·ft) torque @ 6100rpm
• Cast aluminum block with bed plate design split at the crankshaft axis.
• Cast aluminum heads with four valves per cylinder and CNC machined ports and combustion chambers. Valves are actuated through non-rotating inverted bucket cam followers.
• Oil-cooled, forged aluminum pistons from Mahle Motorsport
• Forged steel crankshaft with counterweights, shared crankpins producing an uneven firing interval of 90 or 54 degrees.
• Double VANOS system which varies both intake and exhaust cam phasing
• 10 individual electronically controlled throttle butterflies
• Knock sensors have been eliminated by utilizing the "ionic current" measuring system. Using the ionic current system, engine misfires as well as knock can be measured simultaneously. The ionic current is measured by passing a low voltage across the spark plugs immediately following the ignition spark. NGK supplies this specific dual purpose spark plug (model: LKR8AP) and there are no compatible equivalents from other spark plug manufacturers.
• Quasi-dry sump lubricating system
• The firing order for the S85 engine is 1-6-5-10-2-7-3-8-4-9.

Awards

In 2005, the first year that it was nominated, the S85B50 won four different International Engine of the Year awards in the following 4 categories:

• International Engine of the Year, BMW 5.0 Litre V10 (M5,M6)
• Best Performance Engine
• Best New Engine
• Best Above 4.0 Litre

In 2006 the S85B50 won several International Engine of the Year awards, winning in the following 3 categories:

• International Engine of the Year, BMW 5.0 Litre V10 (M5,M6)
• Best Performance Engine
• Best Above 4.0 Litre

In 2007 the S85B50 won several International Engine of the Year awards, winning in the following 2 categories:

• Best Performance Engine
• Best Above 4.0 Litre

In 2008 the S85B50 won an International Engine of the Year award, winning in the following category:

• Best Above 4.0 Litre

See also

• List of BMW engines
• BMW M5
• BMW M6

References

External links

• The UnixNerd's BMW S85 engine page with photos, history and common problems.