Inspection Info - Description of the Tests
IM240 Test Procedure for 1992 & Newer Vehicles
- The process begins by driving the vehicle onto the dynamometer, activating the vehicle restraints, positioning the engine cooling fan and placing the exhaust collection device (probe) over the tailpipe.
- The dynamometer acts as a "rolling road", allowing the vehicle to be driven as it would in normal traffic while remaining stationary in the test lane. The dynamometer applies loading to the vehicle's drive wheels in proportion to its weight and aerodynamic properties in order to accurately simulate real driving.
- The inspector drives the vehicle according to a prescribed cycle displayed on a video screen. The inspector follows the cycle by using the accelerator and brake pedals as needed in order to speed up or slow down as dictated by the IM240 drive trace.
- The video screen displays a line corresponding to the preset IM240 drive trace. A separate cursor represents the speed of the vehicle being tested.
- At the end of the test, 240 seconds later, the vehicle will have travelled approximately 3.2 km. The average speed of the cycle is 48 km/hr and the peak speed reached is 92 km/hr.
- The length of the IM240 test varies depending on the vehicle's emissions. Emissions readings are sampled on a second-by-second basis and a calculation of the mass of hydrocarbons, carbon monoxide, and oxides of nitrogen is performed.
- After a minimum of 30 seconds of operation on the IM240 drive trace, the computer compares the total mass of the three pollutants with a standard table derived from thousands of actual tests. This table contains readings corresponding to the levels achieved by vehicles that passed the test at the 240 second mark from the 30th second to the 239th second.
- If all of the pollutants are found to be at levels equal to or less than these reference values, the test is terminated and the result is called a "Fast Pass". In such cases, it is not necessary to complete the full test as there is statistically almost a zero chance of that vehicle failing the test in the event that it were allowed to continue to the end. In practice, most vehicles are able to "Fast Pass" and the average time for an IM240 test is in the region of two minutes
Watch a video describing the
IM240 test procedure.
