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Emissions Component

Can I Add a Catalytic Converter To Help Pass the Smog Test?

Can a catalytic converter be legally installed in a vehicle which originally did not require one? My car passes the smog test if I take it to have the carburetor adjusted specifically for the smog inspection. After the smog check I have to get the carb set back to original settings so I can get decent performance from the engine. I just spent $400 on a rebuild, adjusted by a carburetor shop who then takes it to be smogged. I end up doing this every other year and it usually costs between $200 - $300. It does not fail, except it needs a carb adjustment which a catalytic converter would solve easily and bring the overall readings way down; saving me a lot of money and producing less emissions. Is this something I can do and still pass the test?


Adding a CAT might help emissions but won't help pass the smog test.

Adding a catalytic converter to a vehicle which was originally not designed for one will cause it to fail the smog check. The vehicle will be considered having a "tampered" emissions system. Although it is clear that adding a catalytic converter will effectively reduce your vehicle's engine emissions, the BAR will not allow its addition. A smog check station, whether test only or test & repair, must fail a vehicle when such a modification is identified.

All hope is not lost. The smog referee office might be able to help.

We do suggest contacting the smog check referee's office. Although a regular (privately owned smog station) must fail a vehicle when the addition of a catalytic converter is detected, the smog check referee office may allow it to pass (under very specific circumstances), and issue the vehicle documentation indicating the pass status with it's modification. Further inspections would allow for the cat system modification at a regular smog station. It must be noted that this process is reserved for engine changes, but non the less, it wouldn't hurt to speak with a referee and perhaps have them take a look at your vehicle's current non-catalytic converter emissions configuration. You may contact the Smog Check Referee's Office at (800) 622-7733.

posted by SmogTips Support 07-18-2017 03:52 PM

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