How is the test carried out?

Emission Testing principles are similar whether testing to the American, European or Japanese standards. Similar equipment including a Chassis Dynamometer, CVS (Constant Volume Sampler), and exhaust gas analysers for measuring the gas stored in the sample bag collected during the drive cycle.

The drive cycles are different for the USA, European and Japanese standard. The vehicle for test has to be soaked in a controlled environment with a temperature between 20 and 30 degrees to ensure all oils and coolants are within +/- 2 deg c. The vehicle is soaked for a minimum of six hours before the test. In general we soak the vehicle over night to ensure the vehicle has been soaked sufficiently before testing.

After the vehicle has been soaked and the vehicle conditions are complied with, it is then placed onto the Chassis Dynamometer ready for test. The chassis dynamometer simulates road-going conditions, by providing load and inertia to the driving wheels equivalent to the vehicles weight and size dependant on which regulation is used.

The exhaust system of the vehicle is connected to the CVS system, which takes all of the exhaust gas away from the vehicle and is diluted by background air. A small sample is taken from the diluted gas and placed in a sample bag during the drive cycle. After the drive cycle has been completed the sampled gas from the test can then be analysed.

The highly accurate analysers measure the CO, CO2, HC and NOx from the sampled gas stored during the test. The total volume of air and exhaust gas that has travelled through the system is recorded along with the total distance travelled on the chassis dynamometer. The gases being measured have a known density and thereby the emissions calculation results in grams per kilometre (g/km) can be determined.