im going to test it using an Infrared thermometer.
What readings (celcius), should I be getting on the front and rear weld?
Thatās impossible to guess without a whole lot of the analytical data the specific carās designers used and knowledge of the ambient conditions surrounding the converter AND things like engine load, engine speed, and a whole lot of other technical stuff. And the engineers use it only to ensure that the catalyst is heating up adequately and quickly and not discharging its heat too readily. The heat is necessary for the chemistry.
And it wouldnāt matter. You cannot check the condition of a catalytic converter by measuring the temperature and the pipes going in and the pipes going out. A catalytic converter does not work by converting any component of exhaust fumes into heat energy. It works by the catalyst causing the bonds between the nitrogen and the oxygen atoms to break and allowing the now-free oxygen atoms to be captured by carbon monoxide molecules (CO) and become carbon dioxide molecules (CO2) and even be used by unburned hydrocarbon molecules to bond with the now-free oxygen atoms to āburnā, to bond with the oxygen atoms to form CO2 and H2O. The heat from these chemical reactions passes through with the exhaust and has insignificant effect on the shellsā temperatures. Overwhelmingly most of the heat in the cat converter comes from the combustion process within the engineās cylinders, passed to the ceramic substrate in the converter and to the extent practicable retained there to allow the catalyst to do its job. The catalytic process requires heat energy (atomic activity) to cause the bonds between the nitrogen and oxygen atoms in the NOx to break.
Put differently, the pipe going in will always be hotter than the pipe coming out because of the ceramicās heat retention abilities, and it means absolutely zero as a measure of the converterās efficiency.
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You have a cat EFFICIENCY code, not a code saying itās plugged. And flow is the only thing youāll be testing with a thermometer. The P0420 is basically a code saying that the rear O2 is not sensing that the exhaust is being cleaned up enough by the cat to make the EPA happy. A new cat is most likely going to cost less than a hundredth of the cost of the testing equipment.
Huh . . . ?
Please explain how youāll be testing flow with a thermometer
P0420 merely indicates the downstream sensor is switching at a rate, which is too close to the rate of the upstream sensor
The sensor does not sense how clean the exhaust is. The sensor measures oxygen, nothing more, nothing less
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Well I tested the pipe coming out the cat I got 240 Celsius, last night I tested the cat from the top, with the laser aimed at the actual cat, and I get 138 Celsius.
mazda 1.6L engineā¦
This guy says 350-500 degF (177-260 degC) into converter with a rise of 100-150 degF (56-83 degC) across the converter:
How do you know it is warranted for 8 years?
How you know this guy is a licensed mechanic???
You know what my mechanic told me?
HOW TO PASS ETEST:
- clear the code, reset the trip
- wait for the code to reappear (watch at what mileage it comes back)
- clear the code, drive to about 90% of the observed mileage, that should indicate that there is sufficient data on the computer for an etestā¦and since there is no CEL code on-------------> take it for an etest.
What do you guys think about this?
I did exactly what I my mechanic requestd me to do, the CEL came back at 113kmā¦so I am thinking of clearing the code, and retaking it for an etest when its at about 100km.
I donāt think that would work in California. Might work elsewhere though. Worth a shot I guess. Esp since your mechanic seems to have experience it will work.
The catalyst (platinum-palladium) has to get above 350F to begin breaking the bonds between the nitrogen atoms and the oxygen atoms. Remember that temperature is a method of measuring atomic activity, and below that activity level the catalyst will not perform its function.
Butā¦ because it gets hot does NOT mean itās functioning as a catalyst. If itās coated with any residue that interferes with the intimate contact between the NOx and the platinum-palladium, the bonds between the nitrogen and the oxygen will not be interfered with and the converter will not separate the two. If it doesnāt, thereāll also be no additional free oxygen atoms for the carbon monoxide to grab or to allow any unburned hydrocarbon molecules to separate and bond to oxygen atomsā¦ the so-called āsecond burnā.
In short, because a converter gets beyond 350F in its intake, and rises 100 to 150F at its exit does NOT mean itās performing its function.
Extreme cat converter temperatures (cherry red, anyone?) do indicate a flow restriction, which is another possible failure mode of a converter, but you cannot test a converter for function simply by measuring its temperature.
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