An emission test cycle, also known as a smog check, is a specified procedure for measuring pollutant 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 were tested, with the result that real-life emissions would be much higher than expected, undermining the standards and public health.

Application

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 - for just a single engine
• vehicle test stand (also "chassis dynamometer" or "chassis dyno" or "emission dyno") - for the complete car with engine

See also

• Emission standards
• Engine test stand

External links

• Dieselnet overview of commonly used test cycles
• Cycle beating and the EU test cycle for Cars European Federation for Transport and Environment, November 1998
• Poor European test standards understate air pollution from cars European Environment Agency news release. Copenhagen/Amsterdam, 19 October 2004.