Whats wrong with emissions test like the annual inspection (smog check)?
Many people ask why I am so positive about this type of drive-cycle test, but so sceptical about emissions tests of the sort typically used for annual inspection tests (like the Smog Check in the US, or the MoT in the UK). Aren’t they basically the same thing? The answer is – no, not at all. Here are just a few of the important differences: Initial conditions: Emissions vary greatly according to the state of the test vehicle – temperature of oil, coolant, and (especially) the catalyst make a very large difference. Although vehicles are always in a “warmed up” condition for an inspection test, there can be huge differences depending on how the vehicle was driven immediately before the test. On a drive-cycle test like FTP75 or ECE+EUDC, the vehicle is “soaked” at a constant 25C for at least 12 hours before the test begins, to ensure consistent start conditions. Load and speed: The annual emissions test is usually only conducted at one, or perhaps two, load/speed conditions (typically, th
