New generation of lambda sensors by Bosch

With the emission limits in exhaust legislation becoming ever stricter, exhaust sensors are becoming increasingly important. At the same time, manufacturers are becoming increasingly demanding with respect to sensors’ installation space, measurement accuracy, and robustness.



For this reason, Bosch is continuously driving the development of lambda sensors forward. It is now launching the LSF Xfour, the successor generation of the tried and tested LSF4.2 switching-type sensor. The new lambda sensor is smaller and more robust, and its measurement accuracy has been improved. In addition, it responds faster following a cold start.





Faster and more accurate, smaller and more robust

Compared with the LSF4.2, it takes half as much time to reach control mode following engine start. This significantly reduces the amount of time in which the engine’s emissions are uncontrolled. Combined with greater measurement accuracy, this will make it easier to comply with future exhaust standards. In addition, environmental impact is reduced. As overall length is shorter, the installation space needed for the entire sensor assembly has been significantly reduced, while increasing temperature resistance at the same time. As a result, there is greater choice when deciding where to install it in a passenger car’s exhaust tract. All variants of the sensor element can be equipped with a thermal shock protective coating as an option. This improves the sensor’s resistance to condensation in the exhaust tract following a cold start.



Multifunctional exhaust sensor, simple principle

Upstream of the catalytic converter, and occasionally downstream of it, the lambda sensor measures the oxygen content in the exhaust. This is an indicator of combustion quality. For one kilogramme of gasoline to be burned completely, roughly 14.7 kilogrammes of air are needed. The ratio of the mixture in the combustion chamber to the optimum mixture is known as lambda. Conventional gasoline combustion processes ideally operate at a setting of ‘lambda equals one.’ If lambda is smaller than one, the mixture is rich, with too little oxygen. If the ratio is greater than one, combustion is lean, with an excess of oxygen. This is the case with diesel engines, for example, or lean-burn gasoline engines. The switching-type sensor, which delivers an abrupt sensor signal when it detects a transition from a lean to a rich mixture, allows the optimum stoichiometric air-fuel mixture (? = 1) to be set precisely.



| Bosch