Lowering Emissions from the Start

On the basis that the faster a diesel engine starts and maintains stable operation, the lower exhaust emissions will be, a new product for passenger cars from cold-start specialist Beru AG addresses engine emissions as much as cold starting itself.

In contrast to traditional glow-plug systems, the new Instant Start System from Beru can intervene in the combustion process at any stage of engine operation. It is electronically controlled in conjunction with the engine management system.

In contrast to traditional glow-plug systems, which assist engine start-up and then turn-off, the new Instant Start System (ISS) from Ludwigsburg, Germany-based Beru can intervene in the combustion process at any stage of engine operation, the company says.
 
Operating in conjunction with the control unit of an electronically managed engine, it aims to ensure optimum combustion conditions during the phases which continue to recur while an engine is operating normally and lead to an increase in the concentration of exhaust pollutants.

Such phases include idling or after extended periods of overrun. At the same time the ISS device targets petrol-style key start, i.e. starting without preheating at temperatures as low 32 degrees F and with only two seconds of glow plug operation at -77 degrees F.

The main components of the ISS are an electronic control device and specially developed steel glow plugs. The control module regulates the voltage of each plug individually, to achieve not only a heating up time lasting no more than two seconds but also enabling controlled post-glowing and interim glowing. These properties ensure immediate stable idling and the ability for the engine to accept increased load evenly and thus with lower exhaust emissions levels, Beru says.

The glow plugs used for the ISS device are optimized in terms of functional safety and long service life, Beru notes. In spite of reduced power consumption, they heat up exceptionally fast due to advanced design features comprising the concentrated use of power at the tip of the incandescent plug, a new combination of the coil that carries the current, improved heat transfer between the heat coil and the surface of the glow plug sheath and increased heat-up voltage compared to the nominal voltage.

A vital function of the control unit, Beru states, is glow-plug voltage regulation. Temperature behavior and power consumption of the glow plugs is adjusted to the actual requirements of the engine, and voltage during cold start is regulated in four distinct phases. These comprise almost complete voltage (11.5 v) for two seconds to ensure fast heating up followed by three incremental reductions down to 5.3 volts for continuous operation. The control unit communicates with the engine controller by means of a customerspecific software module and assumes control and safety functions. It ensures that power consumption of each plug is set by cycling the glow current; that if the engine is re-started a plug that is already heated does not receive current that after heating-up, the post-glow period of the plug continues until combustion in its cylinder is stable; that in the event of a short circuit, the current circuit to the plug in question is cut off; and that the voltage to a plug is increased again if it cools off, for example due to impingement by cool intake air.

Interim glowing takes place when necessary, for example after extended overrun if engine temperature has reduced. In a special feature, the system prevents the simultaneous turning on or off of all glow plugs to avoid high instantaneous loads on the onboard electrical power system. Beru notes that all these measures ensure continuous stable combustion process and help to avoid hot running problems, uneven engine running, diesel knocking and excessive vibration.

In practice, these benefits have been instrumental in allowing engines from various manufacturers to meet both current (Euro 3) and future (Euro 4 beginning in 2005) emission requirements or Tier 2 and LEV II in the United States. Audi, BMW and Volkswagen are already using the ISS, with Mercedes-Benz planning to equip all diesel engine passenger cars with the Beru Instant Start System as standard equipment beginning with the 2004 model year. Isuzu is also due to equip a V-8 engine for three light trucks with it in the U.S.