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M6 Cabrio - e64 (2006 - ...) |
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Page 7 of 8 High-pressure double-VANOS and single throttle butterflies
BMW’s variable double-VANOS camshaft control ensures optimum management
of the gas charge cycle with extremely short adjustment times in the interest
of enhanced performance, an even better torque curve, optimum response,
greater fuel economy, and cleaner emissions.
Reflecting true motorsport technology, each of the ten cylinders features its
own throttle butterfly, with each row of cylinders being masterminded by
a separate adjuster. While being extremely demanding in mechanical terms,
this is the best operating principle to ensure spontaneous engine response.
To allow smooth and sensitive response of the engine at low speeds, on the
one hand, and to ensure an immediate response of the car whenever
the driver wishes to enjoy high power, on the other, the throttle butterflies are
masterminded by fully electronic management with the position of the gas
paddle being permanently monitored by sensors.
To reach their maximum opening point, the throttle butterflies take just
120 milliseconds – approximately the time even a routined driver requires to
press down the gas paddle. Clearly, this means an immediate response
on the road, the driver enjoying all the spontaneous power and performance of
the engine. And at the same time electronic operation of the throttle butterflies
keeps the transition from engine overrun to part load and vice versa extremely
smooth and harmonious.
The V10 power unit draws in the air required through ten flow-optimised intake
funnels leading out of two air collectors. The funnels and collectors are
made of an extra-light composite material with a 30 per cent share of glass-fibre.
Twin-chamber stainless steel exhaust system.
As important as the intake side is for supreme engine performance, it is
naturally just as significant to consider the exhaust system. In elaborate
computer simulations, the two 5-in-1 fan-type manifolds have been optimised
for equal length and smoothness. To ensure the same accuracy in manifold
diameter, the seamless stainless steel types are shaped and configured from
inside in an interior high-pressure moulding process, under pressures of up to
800 bar. As a result, wall thickness on the intake manifolds is just
0.8 millimetres or 0.03´´ – yet another clear sign of the painstaking attention
the engineers at BMW M have given to even the smallest detail.
The exhaust system of the BMW M6 Convertible extends all the way back to
the silencers in two chambers, finally leading to four tailpipes characteristic
of all BMW M Cars. In all, four tri-metal coated catalytic converters clean the
car’s exhaust emissions in accordance with the EU4 standard.
Engine control unit unique the world over.
The high engine speeds and the large number of control and management
functions obviously demand the utmost of the engine management system.
Hence, the three 32-bit processors are able to handle more than 200 million
instructions per second (MIPS), calculating the right ignition timing, cylinder
charge, injection volume and timing point individually for each cylinder.
Camshaft angle and spread as well as the position of the single
throttle butterflies are calculated by the system at the same time in a fully
synchronised process.
Pressing the Power button, the driver is able to call up an even more sporting
driving program using the full power and performance of the engine.
This activates an even more progressive control map masterminding gas
paddle travel and the throttle butterfly opening, and re-configures the
dynamic engine management functions for an even more spontaneous
response. This changeover function is also configured and retrieved by means
of the MDrive button.
Electronic control of the throttle butterflies is based on the driver’s commands
in pressing down the gas pedal, being set to the ideal position and adjusted for
the additional drive power required by the engine’s ancillary units such as
the a/c compressor or alternator. Functions such as idle speed control, exhaust
gas management and knock control are likewise coordinated and harmonised
to match the current Dynamic Stability Control (DSC) and Engine Drag Control
functions. And last but not least, the engine management system performs
various diagnostic functions and masterminds a number of peripheral units.
Another highlight in engine management: ion flow technology.
Yet another highlight in engine management is ion flow technology serving in
particular to detect any inclination of the engine to knock, that is any undesired
self-ignition of fuel within the cylinders. Ion flow technology thus determines
any such knocking tendency via the spark plugs, also supervising the ignition
process and determining any misfiring of the engine directly in the combustion
process.
Data obtained in this way is transmitted to the engine management unit for
further analysis. The engine controller will then intervene where required
specifically on each cylinder, for example to adjust the ignition timing ideally to
the combustion process via the knock control function. The final advantage
is that spark plugs with such a dual function facilitate diagnosis of the engine
in service and maintenance.
The ideal partner for lots of power: seven-speed SMG gearbox.
The concept of a high-speed power unit serves to convert the torque
developed by the engine into optimum power and performance on the road
through a short overall transmission ratio. And featuring the SMG Sequential
M Gearbox with seven gears and Drivelogic, the BMW M6 Convertible has
exactly the right manual gearbox to convey all the power of the V10 ideally
via the drivetrain to the wheels. It also allows manual selection of gears with
an extremely fast gearshift as well as comfortable cruising with automatic
selection of gears.
Using seven-speed SMG, the driver is able to shift gears both via the selector
lever in the centre console and by means of paddles on the steering wheel.
In the process he is not even required to press a clutch pedal and can even
leave his foot on the gas pedal while shifting gears. When shifting down,
the engine gives interim gas fully automatically, with gears shifting in a smooth
process even faster than a skilled driver would be able to shift gears
manually. The interruption of power flow inevitable when shifting gears is
hardly perceptible, offering the driver even greater pleasure at the wheel
also in shifting gears.
Shifting gears with SMG also enhances traffic safety: With the gearshift being
equally fast and precise at all times, and therefore absolutely reproducible,
the driver no longer has to concentrate as much as usual in choosing exactly
the right gear, SMG thus ensuring a precise, safe and relaxed style of motoring.
Drivelogic: the driver determines how SMG shifts gears.
The Drivelogic function provides no less than 11 individual gearshift options
adjusting the SMG gearshift characteristics individually to the driver’s style of
motoring. The first fundamental point is that these driving programs differ from
one another through the gearshift time preselected – the higher the program,
engine speed and load, the faster the gearshift. Six of the 11 gearshift options
can be preselected within the sequential manual shift function (S-mode),
ranging in their characteristics from well-balanced dynamics all the way to
ultra-sporting performance.
In the S-mode the driver always shift gears manually, with the exception of the
Launch Control function supplementing the purist and sporting S6 driving
program and enabling the driver to accelerate with optimum performance from
a standstill in the interest of the fastest possible acceleration times. In this
case the driver is not even required to shift gears all the way to the top speed
of the car, since the transmission shifts up automatically from first to
seventh gear shortly before reaching maximum engine speed. A special
display informs the driver in each case of the gear currently in mesh.
Five of the 11 drive programs offered by Drivelogic come in the automated
D-mode, with the transmission shifting the seven gears automatically as a
function of the driving program, the current driving situation, road speed,
and the position of the gas pedal. Again, the individual programs in the
D-mode vary through different levels of shift performance offering a higher
or lower standard of dynamics, whatever the driver prefers.
The driver is also able to influence the automatic gearshift by taking back the
gas paddle more slowly in order to shift up also in the D-mode. Conversely,
he is able to shift back more quickly by pressing down the gas paddle in full.
Both in the S- and D-mode, the transmission shifts back automatically to first
gear whenever the car comes to a standstill, then requiring the driver to merely
press down the gas pedal in order to continue.
Special functions for enhanced safety and motoring comfort.
The seven-speed SMG gearbox supports the driver not only in offering
supreme performance of the same standard as in motorsport, but also through
a wide range of safety features. When shifting back on a slippery surface,
for example, SMG instantaneously disengages the clutch to prevent the car
from swerving due to high engine forces suddenly acting on the drive wheels.
On uphill and downhill gradients, the hill detection function changes the usual
gearshift points, avoiding the “pendulum” gearshift phenomenon when driving
uphill. Driving downhill, in turn, the transmission keeps the lower gears in
mesh longer than usual in order to capitalise on the brake forces generated by
the engine. And last but not least, D-mode adjusts the selection of gears to
any uphill inclination of the road.
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