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1 Series - 3 and 5 doors e81/e87 (2007 - ...) |
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Page 3 of 8 Brake Energy Regeneration: generating electric power while
applying the brakes.
Another new feature serving to optimise the car’s efficiency is Brake Energy
Regeneration now to be admired not only in the BMW 130i, but rather in all
new gasoline and diesel engines featured in the BMW 1 Series.
Brake Energy Regeneration serves to concentrate the generation of electrical
energy for the on-board network on periods of engine overrun and application
of the brakes. Such energy management geared to current driving conditions
is made possible by intelligent alternator control, with Brake Energy
Regeneration offering two benefits in practice: First, generation of electrical
energy under such specific conditions ensures a significant reduction in fuel
consumption. Second, the driver himself benefits from the alternator being
disconnected when driving under load, since discontinuation of energy
generation when the engine is pulling the car, for example, when accelerating
and at high speeds, provides more drive power for more dynamic motoring,
meaning not only greater all-round economy, but also enhanced driving
pleasure.
With such on-demand control of the alternator increasing the number of load
cycles, intelligent alternator control comes together with modern AGM
(absorbent glass mat) batteries much more stable than conventional lead acid
batteries. An AGM battery holds the acid in micro-glass fibre-mats between
the layers of lead, thus retaining its energy storage capacity for a long time
even when frequently charged and discharged.
Direct is more effective: gasoline power unit with High Precision
Injection.
Enhanced driving dynamics, optimum weight reduction, and fuel efficiency
raised to a new standard – these are the objectives pursued by BMW’s engine
development specialists under the heading of Efficient Dynamics. One result
of this approach is High Precision second-generation direct gasoline injection
featured in the newly developed four-cylinder power units of the BMW 1 Series.
High Precision Injection allows a significant reduction of fuel consumption
without the slightest loss of power also in everyday motoring. This is made
possible by running the engine in the lean burn mode throughout most
of its speed range, and requires extremely economical dosage of the gasoline
component in the fuel/air mixture.
BMW’s engineers have created the foundation for direct gasoline injection
through the introduction of piezo-injectors. Fitted between the valves in
the cylinder head and injecting fuel into the cylinders at a pressure of 200 bar,
these injectors allow particularly fine and precise dosage of the fuel/air mixture.
Their injector nozzles respond extremely quickly and consistently to the
injection pulses transmitted electronically by the engine control unit, piezoinjectors
thus ensuring particularly precise dosage of fuel in the interest of a
controlled, clean and efficient combustion process.
Despite the confined space within the cylinder head, the injector unit used
on BMW High Precision Injection is for the first time positioned directly next
to the spark plug where the piezo-nozzles opening up to the outside form a
stable, conically-shaped jet of fuel leading into the combustion chamber.
Contrary to wall-guided fuel injection, that is the conventional method used
so far, this jet-guided process allows a much faster and, in particular, more
efficient process of fuel/air mixture formation in the immediate vicinity of the
spark plug. And it avoids the usual loss of fuel along the walls of the cylinder, a
problem encountered in the past with the first generation of direct gasoline
injection.
Precisely this concept provides the stratified charge effect characteristic of the
lean burn mode, with various, intersecting layers of different fuel/air mixtures
forming within the combustion chamber, the share of gasoline in the mixture
consistently decreasing at an increasing distance from the spark
plug. Hence, a particularly rich and therefore ignitable fuel/air layer is available
only in the direct vicinity of the spark plug. As soon as this layer ignites,
the leaner layers at a greater distance from the spark plug burn in a smooth,
consistent and clean process.
The special shape and configuration of the injectors as well as their optimum
position maintains the high precision of the fuel/air mixture process throughout
a broad range of operation and running conditions, thus ensuring lean burn
operation also at higher engine speeds and under higher loads.
Precisely this is a significant reason for the greater fuel economy offered
by High Precision Injection versus first-generation direct gasoline injection.
Combined with catalytic converters positioned close to the engine and
an NOX storage catalyst, all BMW power units with direct gasoline injection
comply with the Euro 4 emission standard.
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