2. Normative aspects. Homologation or approval tests

Some tests have to comply with manufacturer-internal specifications or standards defining the procedures and conditions under which the test is to be carried out. This practice makes it possible to compare the results of different engines tested under the same conditions. This is the case for verifying the performance of manufactured engines, or the reference curves of an engine type, approved by an approved body. In other cases, a standard defines the conditions and even the engine on which the test must be carried out, in order to compare the performance of lubricants or fuels, for example. As the performance of an internal combustion engine is highly dependent on ambient air conditions, a standard defines the reference conditions and any corrections to be made.

Pollutant emissions from internal combustion engines and vehicles are measured on standardized cycles,...