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1 Series - 3 and 5 doors e81/e87 (2007 - ...) |
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Page 5 of 8 Further enhancement of fuel economy: automatic Start/Stop for zero
fuel consumption.
Reducing average fuel consumption was the topmost objective in developing
the power units for the new BMW 1 Series. Hence, BMW is once again
making a significant contribution to the self-commitment by the European
automotive industry to reduce the CO2 emissions of all newly registered
European cars to a fleet average of 140 grams/km by the year 2008. Indeed, to
continue the process of reducing fuel consumption and, accordingly,
emissions from the engine, BMW’s engine development specialists have in
the meantime introduced a number of significant innovations in various areas.
Apart from improvements and new concepts affecting the engine directly, they
have made substantial progress also on the ancillary units around the engine.
An important part of this concept is the automatic Start/Stop function featured
in combination with BMW’s new four-cylinder gasoline and diesel engines
on all manual gearbox versions of the BMW 1 Series. This system automatically
switches off the engine whenever it is not needed, thus reducing fuel consumption
when stopping at the traffic lights, for example, to zero: As soon as
the driver moves the gear selector lever to its neutral position and takes his
foot off the clutch, electronic engine management will switch off the engine
completely. To start the engine once again, all the driver has to do is press
down the clutch pedal, the engine then starting instantaneously without any
further action on the part of the driver.
In the EU test cycle this function helps to significantly reduce average fuel
consumption, providing particular savings above all when driving most of the
time in city traffic.
The automatic Start/Stop function is activated each time the driver starts the
engine and is used in practice as soon as the oil in the engine has reached
its normal operating temperature.
For reasons of safety and motoring comfort, the automatic Start/Stop function
is deactivated under certain conditions, for example if the battery is almost flat
or in very high (more than 30 oC/86 o F) or very low (below 3 oC/36 o F) outside
temperatures. The engine will also go on running during a short interim stop
as long as the interior temperature within the passenger compartment has not
yet reached the level chosen on the air conditioning or if heating power is
required to de-ice or de-mist the windscreen. And last but not least, the driver
is able to deactivate automatic Start/Stop at any time simply by pressing a
button.
Whenever the engine has been automatically switched off, it will start again
without delay as soon as the battery charge reaches too low a level, as
soon as pressure within the brake system drops below a certain point – for
example after the driver has pressed down the brake pedal several times with
the engine switched off – or if the vehicle starts to roll forwards or backwards.
A further point is that the system is able to distinguish between a short stop,
on the one hand, and the end of a journey, on the other. Accordingly, the
engine is not started again automatically as soon as the driver, with the
engine switched off, unlocks his seat belt, opens his door, or lifts up the
engine compartment lid.
New functions in the BMW 1 Series also offer ideal conditions for the effective
use of fuel while motoring. Precisely this is why the BMW 1 Series with
BMW’s new four-cylinder gasoline and diesel engines come with a
shift point indicator. In this case, electronic engine management calculates the
optimum point for shifting up in the interest of enhanced fuel economy,
depending on driving conditions and current requirements. This is done by the
shift indicator – an illuminated arrow symbol specifying the optimum gear –
in the instrument cluster encouraging the driver to shift gears in good time.
Mechanical disconnection of ancillaries to save energy.
Further technologies for saving fuel do not even require intervention by the
driver. One example is active control of the air flaps in the radiator grille
of the new BMW 1 Series, where the flaps are closed as long as the engine
does not require enhanced cooling. Several ancillary units normally driven
by belts or gears in the new BMW 1 Series may be disconnected from the
engine when not required in order to reduce the consumption of energy
under such conditions. These units are thus activated and driven electrically
only when they are really required. Hydraulic pressure in the EPS Electric
Power Steering, in turn, is only built up when the driver really needs steering
assistance.
A further point is that the power steering in the new BMW 1 Series uses
hydraulic fluid with a higher level of viscosity reducing friction within the steering
system. The electrical coolant pump, to mention another example, operates
independently of engine speed and therefore cuts in as a function of
temperature only when really required, again in the interest of enhanced
engine efficiency. In practice this means that the electric coolant pump,
requiring power of only 200 Watts, consumes only about one-tenth of the
drive energy required by a conventional pump.
Yet a further ancillary unit wasting energy on a conventional engine when
switched off is the air conditioning compressor normally driven by a belt and
thus remaining in operation at all times. In the new BMW 1 Series the belt
drive for the a/c compressor features a clutch disconnecting the compressor
as soon as the driver switches off the air conditioning and thus reducing
drag forces from the compressor to a minimum.
Further improvements in fuel economy are provided by pressure-controlled
fuel pumps, special light-running fluids in the transmission, and the reduction
of fluid in the final drive. And yet another point is that the new BMW 1 Series
comes as standard on special tyres reducing roll resistance – and, therefore,
the loss of energy in this area – to a minimum.
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