In 2000, BMW began supplying V10 engines to the Williams F1 team. The new trend of V10 engines on F1 circuits dawned 5 years prior to BMW’s entry and it spawned a new age of high-revving, near 1000bhp monsters. BMW’s opening attempt was plagued with time restraint issues but the end product was a masterpiece that pumped out 810 horsepower and could rev to an astonishing 17,500rpm while only weighing 129 kilograms. The success that BMW saw with these new V10 engines inspired them and they decided to make one for a road going car.
Dubbed the S85, BMW’s new naturally aspirated 5 litre V10 entered the world powering the 2005 E60 M5. The engine itself was very advanced, with many motorsport inspired features staying in the designs. The motor used quasi-dry sump technology, adding another sump to the engine with a secondary electrical scavenge pump. Conventionally, a sump stores oil at the bottom of the engine under the crank shaft, adding height to the engine. A solution to this is the inclusion of a dry sump; an oil storage area located away from the engine. This is not common practise due to the added complexity of this system, however as it’s located away from the heat radiating from the motor, the oil can be much cooler. The biggest advantage however is the reduction in engine height, allowing for a lower centre of gravity and therefore better on-road handling.
Each cylinder of the S85 had it’s own individual, electrically actuated throttle body to allow much more precision over the fuel and air mix entering the combustion chamber, a technology that even still, is uncommon on production cars.
The S85 eradicated cylinder liners in the cooling system and instead opted for crossflow cooling, with every cylinder having a feed directly from the radiator. The radiator itself is split in to two sections, where each section supplies a single bank.
The S85 employed BMW’s famous VANOS variable valve timing system which emerged when the oil pressure reached 115 bar. Each bank of the S85 had 2 camshafts, with both the intake and exhaust cams being actuated when the VANOS kicked in. Both the block and the head were constructed of cast aluminum, a far lighter material than cast iron which is typically used. The camshafts were driven via a chain to each of the inlet cams from the crankshaft, with a gear-to-gear connection between the inlet and exhaust sprocket.
The naturally aspirated V10 very rapidly became known for its legendary, demonic sound, and for how powerful it was, producing 507bhp at 7750rpm. The engine is amongst the highest power per-1-litre ratios of naturally aspirated production car engines, producing just over 100bhp per litre.
While infamously remembered for it’s role in the M5, the S85 was also used in the E63 M6. When housed in the M5, the engine produced a 0-60 time of just 4.7 seconds, with this dropping to 4.0 seconds when in the M6. At 6100rpm the machine hit its peak torque which was a neck-breaking 520Nm.
This particular power plant had an issue with its connecting rod bearings, being that they wore prematurely. The design of the bearing lacked enough clearance between the journal of the crankshaft and connecting rod bearings which then refused the oil enough access, this could result in catastrophic damage to an already delicate and expensive engine. The S85 also had issues with its actuators; plastic gears inside the actuators wore over time, and when they finally gave up the car entered limp home mode. Actuator failure has been reported from as little as 31,000 miles on the clock.
Despite this, the S85 won 4 awards in 2005 including Best New Engine and Best Performance Engine. With the release of the F10 M5 in 2011, the S85 was laid to rest with BMW opting for a 4.4 litre V8. Now in the age of cylinder and displacement reduction to comply with emission laws, the S85 however will be treasured by many people, despite its costly maintenance, for its ground breaking performance, thrill, and sound.