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done by a lever positioned between the camshaft and the intake valves,
its distance from the camshaft being adjusted infinitely by an
additional eccentric shaft operated by an electric motor. Depending on
the position of the Valvetronic control system, the lever converts the
cam contour into a larger or smaller valve lift, whatever may be
required.
Taking nature as the role model: human beings also apply the
Valvetronic principle
A comparison with the
human being clearly explains how Valvetronic works: Whenever we are
required to make a great effort, we human beings breathe in a deep and
long process of ventilation. Whenever we need less air, we do not
throttle the supply of air by, say, closing our nose or our mouth, but
simply breathe in a shorter, flatter process of ventilation. In a
conventional combustion engine the throttle butterfly is basically
comparable to a human being keeping his nose or mouth at least
partially closed. With its large valve lift (= deep, long ventilation)
and short valve lift (= flat, short process of ventilation),
Valvetronic, on the other hand, is able to breathe in the same way as
nature – always in line with current requirements, without any kind of
throttling effect and therefore with maximum efficiency.
Fuel economy up by at
least 10 per cent: as economical as only a diesel was in former times
Valvetronic offers
the customer direct, immediate benefits, with fuel consumption and
exhaust emissions decreasing, but dynamic performance and the
spontaneous response of the engine improving accordingly. Added to
this there is the even higher standard of running smoothness, since
the valves move only slightly in a precisely controlled process.
The improvement in
fuel economy ensured by this concept of throttle-free engine load
management is approximately 10 per cent in the EU cycle and at least
10 per cent under the typical driving conditions encountered by a
customer. The basic rule is that fuel economy versus other concepts
increases with the driver running the vehicle at lower loads and
engine speeds. The consumption figures the motorist is able to achieve
in this way are comparable to the fuel economy only a diesel engine
was able to offer just a few years ago.
At the same time the
new four-cylinder is even more dynamic than its predecessor, the 316ti
now accelerating well over a second faster to 100 km/h, achieving this
important mark from a standstill in 10.9 seconds. The standing-start
kilometer, in turn, comes after 31.6 seconds, 1.8 seconds faster than
before, and the top speed of the 316ti is now 201 km/h or 125 mph, 11
km/h faster than the top speed of the former model.
Another advantage is
the unusually spontaneous response of the 316ti to the gas pedal. This
is attributable to the simple fact that load control, to use the
technical term for "giving gas", now takes place "right there where
the action is", that is directly in the combustion chamber. This
eliminates the usual time lag between the process of "giving gas" and
the actual acceleration of the car, which used to be inevitable due to
the need to fill the intake manifold between the throttle butterfly
and the combustion chamber. In this respect, Valvetronic even
outperforms the most advanced concepts using individual throttle
butterflies, thus offering an unprecedented combination of spontaneous
engine response and ultra-fine dosage of power and performance under
low loads.
Perfectly suited for
all fuel grades, contrary to a direct-injection (DI) petrol engine
Another significant
advantage of Valvetronic highly beneficial to the customer is that a
Valvetronic engine offers at least the same fuel economy as the most
advanced direct-injection petrol engines without the same compromises
in terms of emissions. Accordingly, the 316ti is able to do without
the elaborate and so far hardly reliable emission management
technologies still required today on a direct-injection petrol engine.
And it does not require sulfur-free fuel like a direct-injection
petrol engine, achieving its superior fuel economy with proven l =1
technology, which allows the Valvetronic engine to run on all
commercially available grades of regular petrol. In other words, the
customer enjoys all the consumption-related advantages of Valvetronic
also when driving in countries without a nationwide supply of sulfur-free
fuel. The consumption figures for the 316ti nevertheless relate to the
use of premium fuel with an octane rating of 95 RON. Together with its
63-liter (13.9 Imp gal) fuel tank, the 316ti offers a much longer
range than its predecessor, with extra-urban fuel consumption in the
European EU test cycle of just 5.3 liters for 100 kilometers (53.3 Imp
gals). This means that the driver would only have to refuel after a
very significant 1,188 kilometers or 737 miles.
Basic engine design
completely revised
Not only the cylinder
head with BMW’s new Valvetronic technology, but also the complete
four-cylinder power unit featured in the BMW 316ti is an all-new
development from the ground up. The new cross-flow cooling concept with
its open deck crankcase reduces coolant flow resistance and therefore
allows use of a smaller water pump with just 60 per cent of the usual
power uptake.
Made of aluminum,
the engine block ends exactly on the centerline of the crankshaft
bearings. A ladder frame between the crankcase and the oil sump
connects the lower halves of the bearing bridges to form one complete
unit also accommodating the balance shaft housing and the two-stage
oil pump. This makes the entire drive unit very stiff and robust,
minimizing any vibration of other vehicle components the driver would
otherwise feel on the steering wheel, gearshift lever and pedals, and
also perceive as a kind of consistent humming noise.
All ancillaries are
bolted directly to the crankcase without the rather elaborate supports
and attachments otherwise required – again an important contribution
to running smoothness with vibrations reduced to a minimum.
BMW’s new
four-cylinder furthermore comes with all modern engine technologies
such as:
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