This article was first published in 2004.
The new BMW M5 uses a naturally aspirated, 5-litre V10 engine developing
507hp (373kW) at 7750 rpm and 520Nm at 6100 rpm. In this story we take a look at
the internals of this astonishing engine.
The engine weighs 240kg, about the same as the previous M5’s V8 engine. It
uses a 90-degree angle between the two banks of 5 cylinders, with a 17mm
crankshaft offset. The cylinder crankcases are made of low-pressure gravity die
cast hypereutectic aluminium-silicon alloy. No liners are present - the
iron-coated pistons run up and down in the uncoated bores. A short-stroke design
is used - stroke is 75.2 mm and bore is 92 mm.
A ‘bedplate’ (a crankshaft girdle) is used to tie the bottom of the engine
together. The bedplate is made from aluminium with integral grey cast iron
inserts used to ensure crankshaft alignment and keep the main bearing clearance
at a minimum over the entire operating temperature range. The inserts help to
reduce the thermal expansion of the aluminium bedplate.
The crankshaft is made of forged, high-tensile steel and is supported by six
bearings. It weighs 21.8 kilograms. The main bearing diameter is 60mm with a
bearing width of 28.2mm. Two conrods connect to each of the five crank pins,
which are offset at an angle of 72 degrees. A cylinder spacing of 98 mm
enables the use of a short crankshaft.
The pistons are made of high temperature resistant aluminium alloy and are
provided with an iron coating. They weight 481.7 grams each, including
piston pins and rings. The compression height is 27.4 mm at a compression
ratio of 12.0:1. The pistons are cooled using oil spray jets which are directly
connected to the main oil duct. The 140.7 millimetre long fracture-split
trapezoidal connecting rods are also made of high-strength steel. Each of the
connecting rods - forged from 70MnVS4 - has a mass of only 623 grams,
including the bearing shells.
As are the crankcases, the single-piece aluminium cylinder heads of the V10
engine are cast at the BMW light alloy foundry in Landshut. The cylinder heads
feature integrated air ducts for air injection, important for rapid catalytic
The valves are actuated by spherical tappets featuring hydraulic valve play
compensation. The tappet diameter has been reduced to 28 millimetres and
mass to 31 grams. The diameter of the intake valve is 35 millimetres, the
exhaust valve measures 30.5 millimetres in diameter. The shafts are 5 mm in
The bi-VANOS variable camshaft control ensures an optimum charge cycle. At
the lower end of the load and engine-speed scale, the car can be driven with an
increased valve overlap, boosting internal exhaust gas recirculation. This, in
turn, leads to a reduction in charge cycle losses and fuel consumption. The
adjustment of the angles as a function of the accelerator pedal position and the
engine speed is infinite and map-controlled. The sprocket, which connects to the
crankshaft via a simplex chain, is linked to the camshaft via a two-speed,
helical gearbox. In the event of an axial displacement of the adjusting piston,
the helical set of teeth turns the cam relative to the sprocket, which allows
for the variation of the angle of the intake camshaft by up to 66 degrees and
the outlet camshaft by a maximum of 37 degrees in relation to the crankshaft.
The M bi-VANOS technology requires very high oil pressures for
ultra-precise, high-speed camshaft adjustment. This is why a radial piston pump
in the crank chamber increases engine oil pressure to an operating pressure of
Four oil pumps provide the engine with lubricating oil. During extreme
cornering, centrifugal forces push the engine oil to the cylinder bank facing
the outside of the bend, thereby preventing the natural return of oil from the
cylinder head, which might lead to inadequate oil supply in the sump. Should the
worst happen, the oil pump could suck air. To prevent this situation, the engine
features a transverse force regulated oil supply system. This system
incorporates two electrically-operated duo-centric pumps which pick up oil from
the outer cylinder head and transport it to the main oil sump if lateral
acceleration exceeds 0.6 g. A lateral-g sensor transmits signals to the pumps.
The oil pump itself is a continuously variable pump with volume control which
delivers exactly the amount of engine oil needed by the engine. This is achieved
by the variable eccentricity of the pump’s rotor in relation to the pump casing,
depending on the oil pressure in the main oil duct. This picture shows the oil
pump at minimum flow....
...and this at maximum flow.
Each of the ten cylinders has its own throttle valve. In order to attain
maximum engine responsiveness in the lower speed range and to achieve an
immediate vehicle response at the high end of the performance spectrum, all
throttle valves are controlled fully electronically. Two contactless Hall
potentiometers determine the position of the accelerator pedal 200 times per
second. The engine management reacts to changes and causes the two actuators to
adjust the ten throttle valves. It takes 120 milliseconds to completely open the
The V10 engine uses ten flow-optimised intake trumpets to breathe air from
two intake plenums. The intake plenums and the trumpets are made of a
lightweight compound material that contains 30 percent fibreglass.
Two stainless steel 5-into-1 high-performance tubular headers have been
optimised for equal length. For exact pipe diameters, the seamless stainless
steel pipes are formed from the inside using an interior high-pressure forming
technique (hydroforming) with a pressure of up to 800 Bar. The manifold
pipes have a wall thickness of just 0.8 mm.
The exhaust system has a dual-flow design all the way to the silencers. Two
trimetal-coated catalytic converters per exhaust line clean the exhaust gases in
compliance with the European EU4 and American LEV 2 standards. There are two
underfloor catalysts. The other two catalytic converters (one for each exhaust
line) are located close to the engine. In conjunction with the thin-walled
exhaust manifolds, these catalysts quickly reach their optimum operating
The MS S65 engine control module is equipped with three 32-bit processors
that perform more than 200 million individual calculations per second. Compared
to the M3 control unit presented only four years ago, this represents a
performance increase by a factor of eight. In terms of memory capacity, the
latest control unit outdoes the previous one by as much as ten times. Receiving
more than 50 input signals, this system calculates for each individual cylinder
and for each individual cycle the optimum ignition point, the ideal cylinder
charge, the injection quantity and the injection point. At the same time this
system calculates and makes the necessary adjustments for the optimum camshaft
angle and the optimum position of the ten individual throttle butterflies.
Ionic current technology (as used by Saab for some time) is used by the
engine management unit to detect engine knock, misfiring and combustion misses.
This technology utilises the spark plug in each cylinder to sense and control
engine knock. It also helps to check for correct ignition and to identify
possible ignition misses. The spark plug therefore has a dual function – as an
actuator for the ignition and as a sensor for monitoring the combustion process.