Emission test cycle
An emission test cycle, also known as a 'smog check', is a specified procedure for measuring pollutant
A pollutant is a waste material that pollutes air, water or soil, and is the cause of pollution.Three factors determine the severity of a pollutant: its chemical nature, its concentration and its persistence. Some pollutants are biodegradable and therefore will not persist in the environment in the...

 emissions of engines. For emission measurements to be comparable for different engines in a category, the measurements are performed under a specific operating pattern, or 'test cycle' of alternating high, medium, and low engine load. The test cycle should ideally reflect a 'normal' usage pattern concerning speed and acceleration. Realistic test cycles are instrumental for the environmental integrity of emission standards. It was recently discovered that engine manufacturers would engage in 'cycle beating' to optimize emission performance to the test cycle against which European vehicle emission standards
European emission standards
European emission standards define the acceptable limits for exhaust emissions of new vehicles sold in EU member states. The emission standards are defined in a series of European Union directives staging the progressive introduction of increasingly stringent standards.Currently, emissions of...

 were tested, with the result that real-life emissions would be much higher than expected, undermining the standards and public health.


Emission test cycles are typical tests for research and development activities on engines at automobile OEMs.

The commonly used hardware platforms therefore are:
  • engine test stand
    Engine test stand
    An engine test stand is a facility used to develop, characterize and test engines. The facility, often offered as a product to automotive OEMs, allows engine operation in different operating regimes and offers measurement of several physical variables associated with the engine operation.A...

     - for just a single engine
  • vehicle test stand (also "chassis dynamometer" or "chassis dyno" or "emission dyno") - for the complete car with engine
  • ASM Test - Accelerated Simulation Mode: (California inspections) Vehicles tested at 15 MPH & 25 MPH where vehicle undergoes a load.

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