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BMW S65 Engine

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BMW S65 Engine For Sale

This engine replaces the S54 unit, compared to which it is completely different. With the birth of the S65 engine, the 6- cylinder in-line architecture, present since 1993, is abandoned in favor of a new, powerful and technological 4-liter V8. Despite the greater complexity of the new drive unit, the final weight is lower than that of the previous 6-cylinder (202 kg against 217). This engine derives from the larger S85B50 unit, the V10 fitted to the BMW M5 E60. But it is not simply the engine of the private 2-cylinder M5: in some ways the engineIn fact, the S65 represents an evolution of the powerful V10, obtained by drawing on the knowledge gained by the German manufacturer in Formula 1 competitions. An even more performing 4.4-liter unit was later derived from the original 4-liter unit.

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The 4-liter engine is described in more detail below.


A "naked" view of a V8 S65 mounted on an M3 The monobloc is made by shell casting using an aluminum and silicon alloy called alusil, which allows, after an appropriate electrochemical treatment, to obtain silicon liners for each cylinder. The two cylinder banks form a 90 ° angle to each other. The engineers of M GmbH, the BMW sports department (formerly called Motorsport ) have focused on this measure to obtain optimal balance and effective vibration reduction. This is also due to a reduced offset between the banks, which also makes the engine more compact and rigid. The measures ofbore and stroke are equal to those of the V10 S85, ie 92x75.2 mm, for a total displacement of 3999 cm³. The compression ratio also follows that of the BMW 5-liter V10, and is thus confirmed at 12: 1. To reduce vibrations in the crankcase, the crankshaft is installed on a racing structure called the "Bedplate", which reduces the backlash of the bench supports. As for the crankshaft itself, made of forged steel, it has relatively small dimensions, both thanks to the aforementioned reduced offset between the banks and thanks to the cylinder center distance, which is also decidedly contained. The connecting rods are made of steel and magnesium and are particularly light, as are the pistons, made of aluminum alloy.


The heads of the S65 engine are made of aluminum alloy. Distribution follows a now classic pattern at BMW. The traditional four valves per cylinder are moved by two overhead camshafts per cylinder bank, which act on the hydraulic bucket tappets. Always respecting the tradition of the house, the camshaft timing is variable thanks to the help of the Doppio Vanos system. In the S65 unit, these systems have been revised so that they can operate without a dedicated hydraulic circuit, but directly thanks to the engine oil pressure. This represents an evolution over the V10S85, which instead has a dedicated circuit.


The lubrication system of the S65 wet sump engine is equipped with two specially designed vane pumps. Depending on the conditions of use of the car, they vary the oil pressure to be sent into the circuit. All this so that there are no false oil drafts in sporty driving conditions, when an excess of centrifugal force could occur during sudden braking or sharp steering, which prevents the correct circulation of the oil. In addition, another feature is the presence of an oil pan divided into two parts.


The liquid cooling system has been specially designed for this engine. The S65 engine is thus equipped with a horizontal flow cooling network, which starts from the base and rises horizontally until it reaches the two heads, then returns to the radiator and resumes the cycle.


As is customary on recent Motorsport engines, single throttle bodies have also been mounted on the S65 unit, one per cylinder, driven by two servomotors, one per bank, in turn governed by the electronic control unit. However, the mass air flow sensor is absent. This solution made it possible to make the incoming air flows more linear.

Exhaust The exhaust system was also designed for the engine. It generates a low back pressure, in order to improve the performance of the engine. The exhaust manifolds are made of steel and have been made by high pressure molding, so they are able to withstand high stresses, both thermal and mechanical.

Power and ignition

The electronic control unit is a Siemens MSS60, it is able to perform 200 million operations per second. Various tasks of primary importance are delegated to the electronic control unit, such as calculating the quantity of air-petrol mixture, the instant of ignition and the instant of injection, as well as the operation of the servomotors that regulate the opening of the throttles. In addition, he must set the cam timing according to the engine load and adjust the idle. The ignition, integrated in the control unit, uses the ionic current of the spark plugs to detect any knocks, knocks and other anomalies relating to the ignition itself.


The performance of this V8 is as follows: maximum power reaches 309 kW (420 hp ) at 8300 rpm, while maximum torque reaches 400 Nm at 3900 rpm. The specific power is therefore 105 HP / liter, an index of the decidedly thrust setting of this engine.


Initially fitted to the BMW M3 Coupé E92, launched in the second half of 2007, this powerful propulsion unit by the end of the same year also ended up under the hood of the BMW M3 sedan E90, while the following year it also found its place in the BMW M3 Cabriolet. E93.


A BMW M3 GTS equipped with the 4.4 liter V8 S65B44 As already mentioned above, a 4.4 liter engine was also derived from the S65B40 engine, called S65B44 and which debuted on the BMW M3 Coupé GTS, a sort of race car approved for road use and produced in a number limited number of specimens starting from 2010. The S65B44 engine experienced its first, and so far only application in 2010: the differences compared to the already powerful 4-liter are first and foremost in the increase in displacement, which went from 3999 to 4361 cm³ thanks to the increase in the stroke of the cylinders from 75.2 82 mm, the latter obtained using a specific crankshaft. The compression ratio is always unchanged, while maximum power rises to 450 hp at 8,300 rpm and maximum torque reaches 440 Nm at 3,750 rpm. Later, starting from June 2011, the S65B44 engine also found application on another particular M3, the BMW M3 CRT, with sedan body.