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It was once again time for a CA smog check and since the previous checks were hovering only slightly below the limits, I thought it was time for a new catalytic converter. My old cat was a universal one from before CA legal cats were specified.
Fortunately I have my exhaust system configured for easy parts swap (V-bands), in particular for the cat, which can also be substituted with a test pipe in case I take the car to the track. Tom M’Guinn has in previous threads showed how to find CARB approved cats for our cars and since my numbers were close I went for the most economical one, namely Walker 81128. Here is a reference to CARB’s webpage with approved converters (just specify make, year, model, and engine): https://ssl.arb.ca.gov/PartsSearchTo...earchTool.aspx
Here is my new catalytic converter (and test pipe):
And here is the test report with excellent numbers (the mileage is actually close to 232k miles):
And just for the record: my tachometer showed 2800 rpm when the test station showed 2600 rpm … so the boost actually comes on 200 rpm earlier than expected
The only “defeats” in the process were time spent and cost ($116 for the converter and $75 for the test).
Random thought...I wonder how your water injection setup would affect NOX reading?
Maybe experiment time...tune it lean for low HC/CO but do a little bit of H2O spray...run a hollowed-out cat for appearances, maybe an unofficial "pre-test"..
Voith - in California all cars since 1976 have required catalytic converters and smog equipment.
Cars older than that are exempt (generally) since there were no real smog laws prior to that year in effect. "Grandfathered in" so to say.
Congratulations! Always great to pass. I'm jealous of your idle-only test, but looks like you would have passed the dyno version with flying colors as well. The state keeps changing its links, but the one you posted is the best yet. Thanks for that! I'm sure that $100 Walker cat works at least as good as the $400 direct-fit DEC car. For that price, I'm inclined to modify my direct-fit DEC pipes so I can just swap in a new one of these for each test. Nothing works better than a new cat, although I have to say these modern replacements don't seem to last very long...
Random thought...I wonder how your water injection setup would affect NOX reading?
Maybe experiment time...tune it lean for low HC/CO but do a little bit of H2O spray...run a hollowed-out cat for appearances, maybe an unofficial "pre-test"..
Water injection in a well-controlled amount would probably lower the NOx numbers.
My water control is much too simple for that. It only comes on over 12 psi boost.
I am happy to see that BMW has caught on to the port water injection idea with their M4 GTS
How do old 30+ years old non catalytic converter cars pass CA smog tests? Are those just banned or is there an exemption on those?
Here cars classified as old timers (30+y old) don't need smog testing, just brakes, lights etc..
Also old timers have 90% discount on insurance and all registration fees. 951 yearly registration costs about 120€.
Originally Posted by V2Rocket
Voith - in California all cars since 1976 have required catalytic converters and smog equipment.
Cars older than that are exempt (generally) since there were no real smog laws prior to that year in effect. "Grandfathered in" so to say.
Too bad we have a fixed year exemption and not a +30 year one. Fortunately we don't have mandatory safety tests here, verifying that the windshield is free from scratches, the wipers have new inserts, etc.
Our annual registration cost is about 30% less than yours.
Congratulations! Always great to pass. I'm jealous of your idle-only test, but looks like you would have passed the dyno version with flying colors as well. The state keeps changing its links, but the one you posted is the best yet. Thanks for that! I'm sure that $100 Walker cat works at least as good as the $400 direct-fit DEC car. For that price, I'm inclined to modify my direct-fit DEC pipes so I can just swap in a new one of these for each test. Nothing works better than a new cat, although I have to say these modern replacements don't seem to last very long...
Thanks.
My hunch on what has happened to the converters are as follows:
In the early days the cat manufacturers used plenty catalyst (platinum, palladium and rhodium), so they could heat up quickly and do their thing. That unfortunately also meant that they would be a little too "eager" if the mixture got too rich, resulting in a melted matrix (ceramic honeycomb).
Then they reduced the catalyst amounts and likely noted, that there was good money to be made if they really skimped on it. My old converter was an example of that, since it was always very difficult to get going.
I am guessing that CARB noted a resulting increase in smog test failures that could be attributed to the converters and set up some functional criteria to get catalytic converters approved for California, resulting in converters with slightly more catalyst, which is what I now have.
04-25-2017, 07:49 PM
Smog Victory
