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The new V8 Power Unit for the BMW M3 - Formula1 foundry Engine block

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The new V8 Power Unit for the BMW M3
High-speed engine
Formula1 foundry Engine block
Oil supply and Intake System
Dynamic Performance and Engine Management
Ion Flow Technology and Spark Plugs
Engine Specifications
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Engine block from BMW’s Formula 1 foundry
The engine block featured on the new BMW M3 comes from BMW’s light-alloy foundry in Landshut near Munich, which also builds the engine block for BMW’s Formula 1 racing cars. The cylinder crankcase is made at the foundry in a low-pressure die-casting process from an over-eutectic aluminium-silicon alloy, with at least 17 per cent silicon. The cylinder liners, in turn, are formed by exposing the hard silicon crystals, the iron-coated pistons running directly in these uncoated honed cylinder bores and thus not requiring any additional lining. Cylinder stroke is 75.2 millimetres or 2.96´´, cylinder bore 92 millimetres or 3.62”, adding up to provide overall capacity of 3,999 cc. Since high engine speeds, high compression forces and high temperatures exert extreme loads on the crankcase, the crankcase is very compact in its design and dimensions and built as a very stiff bedplate structure, a concept which has already proven its qualities in motorsport. Made of die-cast aluminium, the bedplate features grey-cast-iron inlays ensuring very precise support of the crankshaft. In particular, this structure keeps main bearing play throughout the entire range of operating temperatures within close limits, the grey-cast-iron inlays reducing thermal elongation of the aluminium housing. As a result, oil flow remains almost unchanged at all times. And to form a positive engagement with the aluminium frame, the inlays have open cut-outs integrating them directly in the frame.
With the distance between cylinders measuring only 98 millimetres or 3.86´´, the crankshaft made of forged, high-strength steel is relatively short, making it very stiff in terms of flexural and torsional strength and reducing the weight of the crankshaft to just 20 kg or 44 lb. Running in five bearings, the crank-shaft has a main bearing measuring 60 millimetres or 2.36´´ in diameter, with bearing width of 28.2 millimetres or 1.11´´. In each case two connecting rods act on one of the four crankpins offset from one another by 90°.

s65b40_front_view_timing_drive

Lightweight construction specifically on all moving masses
The weight-optimised box-type pistons are cast out of a high temperature-proof aluminium alloy and coated with iron. This reduces their weight to a mere 481.7 grams including the piston pins and rings. Compression height is 27.4 millimetres, with a compression ratio of 12.0 : 1. The pistons are cooled by oil spray jets connected to the main oil pipe. Measuring 140.7 millimetres or 5.54´´ in length, the cracked trapezoidal connecting rods are made of a high-strength steel-magnesium alloy. Including the bearing shells, each connecting rod weighs just 623 grams, which significantly reduces the oscillating masses.
The single-piece aluminium cylinder heads feature four valves per cylinder in characteristic BMW style. The valves weighing 42 grams each are activated by ball-shaped cup tappets with hydraulic valve play compensation. Tappet diameter is only 28 millimetres or 1.10´´, while the intake and exhaust valves measure 35 and respectively 30.5 millimetres (1.38 and 1.20´´) in diameter. Measuring only 5 millimetres or 0.20´´ across, the valve shaft has hardly any influence on flow conditions in the intake manifold, while the hydraulic valve play compensation rules out any change in valve play, ensuring lasting reliability and at the same time reducing the cost of maintenance.

The engine always keeps a cool – cylinder – head
Compared with conventional systems, the cross-flow cooling concept featured on the new V8 power unit significantly reduces pressure losses in the cooling process, spreading out temperatures smoothly and consistently throughout the cylinder head and thus reducing temperature peaks at all critical points. To ensure a perfect flow of cooling around each cylinder, the coolant flows from the crankcase via the exhaust side crosswise through the cylinder head and the collector rail on the intake side to the thermostat and, respectively, to the radiator.

s65b40_cylinderhead

Double-VANOS – but with low instead of high pressure
Focusing on the engine concept, the engineers at BMW M sought from the start to increase engine output through an optimum charge cycle at high engine speeds. Quite simply, this is because reduced charged cycle losses offer not only more power, but also an improved torque curve and optimum engine response as well as a further reduction of fuel consumption and lower emissions. And precisely these are the benefits offered by variable double-VANOS camshaft control introduced in the BMW M3 for the first time worldwide back in 1995. With its extremely short adjustment times, double-VANOS now also perfects the cylinder charge cycle in the eight-cylinder power unit of the new BMW M3. Under low loads and at low engine speeds, for example, double-VANOS ensures a higher valve overlap and, as a result, better internal recirculation of exhaust gasses. This, in turn, reduces charge cycle losses and helps to minimise fuel consumption.
The level of power delivered by the engine depends on the position of the gas pedal and engine speed. So double-VANOS adjusts the precision and angle spread on the camshafts infinitely to these two parameters with precise management by a control map. Unlike the ten-cylinder power unit featured on the BMW M5 and BMW M6, the eight-cylinder uses a double (and not a single) chain to connect the crankshaft and sprocket. The sprocket, in turn, is connected to the camshaft by a step motor/actuator, and not by a helical gearing.
The advantage is that the low-pressure M double-VANOS developed for the eight-cylinder is able, unlike the high-pressure VANOS featured on the V10, to run with regular engine oil pressure acting on the step motor. In other words, there is no need for a separate high-pressure system of pipes to turn the crankshaft versus the sprocket in a relative motion at maximum speed and with utmost precision. This means that the angle on the intake camshaft may be varied by up to 58°, the angle on the exhaust camshaft by up to 48°. Maximum angle adjustment speed, in turn, is 360° per second crank angle, low-pressure adjustment thus ensuring very short adjustment times and providing the optimum adjustment angle synchronised to ignition timing and injection volume as a function of load and engine speed.



 
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