The science of the lambda

Lambda sensors – used for years to monitor the concentration of oxygen in petrol engine exhaust gas – have been applied to a diesel engine for the first time by Bosch.Historically, the high air output of diesel engines has precluded the effective use of lambda sensors.

However, the Bosch Broadband Lambda sensor – developed for direct injection petrol engines – started to make application to diesel engines possible. It was then a matter considerable software reprogramming to enable the sensor to cope with diesel engine patterns.

By feeding back information on exhaust gases to the engine management system, Bosch claims that its lambda control system allows for unprecedented levels of injection and engine tuning, further reducing fuel consumption and emissions.

The lambda-based control optimises exhaust gas quality through a combination of exhaust gas recirculation, charge-air pressure and start of injection. A broad-band lambda sensor with a wide working range measures the oxygen content in the exhaust gas and is able to send important information on the combustion processes in the engine to the ECU, which then alters injection and air-pressure parameters to maintain correct exhaust gas output.

Compared to standard diesel engine management, Bosch says that the new system permits a stricter adherence to low emission values. This gives engines better protection against defects, since harmful combustion in cars running in overrun may be detected and corrected. In engines running in full-load, the system also offers better smoke suppression than before.

According to Bosch, several automotive manufacturers intend to equip their standard diesel engines with the new control system.

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