The Emission Inspection

The first section of Smog Test is the emissions inspection. To pass the emissions inspection your vehicle's engine must be running fairly well, insuring all fuels in its combustion chambers are burning away efficiently and cleanly. Consequently, this is the entire reason for the smog test program.

Smog is formed due to improperly burned fuels. In cases where too much fuel is presented to the engine cambers high levels of Carbon Monoxides (CO) are emitted through the engine tail pipe. In cases where low fuel levels are presented, once again the fuel burns improperly and now the engine produces low levels of CO, but begins to emit high levels of Nitrous Oxides (NOx). The engine may also miss-fire due to inadequate fuel, creating excessive Hydrocarbons (HC).

The optimum performance level is achieved when the engine can maintain a 14.7:1 air/fuel ratio during the combustion process with a constant variation +/- 5% to assist the catalytic converter operation.

In parts of California where smog pollution is higher, vehicle owners are now required to complete an "Enhanced" version of California's smog test. The "Enhanced" smog test requires your vehicle to be driven on a dynamometer while the smog machine collects emissions samples from the tailpipe. The "Enhanced" smog test has been proven to retrieve a more accurate sample of a vehicle's emissions output, then it's predecessor, the "Basic" smog test. The "Basic" smog test requires vehicles to be tested, only at idle and 2500 rpms. "Basic" smog test vehicles do not need to be driven on a dynomometer.

Visible Smoke Test: Beginning in March 2008, all vehicles subject to a Smog Check inspection will require a visual test for smoke. This test is in addition to the standard tailpipe emissions test, and will be conducted by the smog technician.