BMW 2007 Annual Report Download - page 221

21
== 1 – 2
Setting up the technology to
measure and analyse all energy
flows in the vehicle.
== 3
The Auto Start Stop Function
helps to reduce fuel consumption
substantially by switching off the
engine when standing.
As a core vehicle function, switching the engine on and off must be coordinated with the window
regulator, air conditioning, electronic immobiliser system, and a total of 17 other control units on board.
The engineers had to ensure that the engine does not switch off if it is too cold or too hot outside or
simply because the battery gets too low to easily restart the engine after a stop, for instance. Clustered
around the ASSF is a small orchestra of sensors which synchronise how the system is used.
What at first glance appears to be a simple engine function actually comprises a highly-intelligent sys-
tem which affects the vehicle’s whole organism. Today, this function is considered a particularly effec-
tive energy feature of the EfficientDynamics package, offering customers a major benefit without being
at all conspicuous. In the standardised European Driving Cycle it saves around three percent of fuel.
Developers at the BMW Group are currently pulling out all the stops to implement the system in the
Group’s automatic models as soon as possible – up until now it has only been available for manual
transmissions.
And yet their imagination and their pioneering spirit are still far from being exhausted. Among other things
the EfficientDynamics engineers are researching technologies which will tap into an energy source
that has so far been completely ignored: heat. For technical reasons little more than a third of the fuel in
the engine block is converted into operating power; almost two-thirds are lost in the form of waste
heat in the engine compartment and through the exhaust pipe.
But what if we could harness that energy? automotive engineers wondered. What if we could obtain
energy from the heat? The technology to do this is already doing the rounds of test benches at the
Munich Research Centre. In simple terms, the principle of the steam engine is transferred to the auto-
mobile: liquid is heated in two loops to generate the steam to drive a motor – the so-called turbo
steamer. The energy from the exhaust gas produced can be used on the one hand to support the
drive train; on the other hand there is also sufficient energy in the exhaust gas to easily supply the air
conditioning, vehicle computer and navigation system as well as all the electronic consumer loads on
board.
Report: A matter of consistency.
== 3