Spark plugs with integrated pressure transducer, also called measuring spark plugs, are suitable for measuring cylinder pressure in gasoline and gas engines without the need to provide an additional bore in the cylinder head. Various changes to the original spark plug occur when a pressure sensor is integrated in the body of the spark plug such as the spark position and the maximum diameter of the isolator.
This article shows the results that can be achieved in respect of the spark and measurement function on a state-of-the-art, turbocharged, directly-injected gasoline engine with homogeneous mixture operation by comparing the original spark plugs with measuring spark plugs. To this end, various engine operating points were carried out at full and partial load by varying the lambda and spark ignition timing, which were assessed as a reference based on water-cooled pressure sensors.
The measuring function as well as the spark function yielded good results where trade-offs had to be made in the threshold areas of the spark timing and lambda variation carried out with respect to the function of the measuring spark plug. These could, however, be due to the changed installation of the ignition coil.