catalyst efficiency

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3 years 1 week ago #47519 by birsch
catalyst efficiency was created by birsch
Is it possible to do a Catalytic converter oxygen storage test using O2 sensor comparison when the upstream is an AF sensor and the downstream is a narrow range sensor? Won't the different reaction times cause the waveforms to be not in sync? Thanks

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2 years 11 months ago #48115 by Flatrater
Replied by Flatrater on topic catalyst efficiency
Yes it is, but you'd use locus length instead of freq comparison.

The real question is why you'd want to perform the oxygen storage test as it does not give you the condition of the catalyst.

For decades, fuel control has been so tight that oxygen storage isn't needed for the catalyst to operate. Paul Baltusis of Ford brought attention to it decades ago. Check out his resume which includes 20 or so patents. It's also in SAE white papers and patents.

It turns out that catalyst efficiency is difficult to monitor. While oxygen storage is not necessary for catalyst operation, it "correlates" to the efficiency when used. Right now, this is all the OEs have to work with in order to satisfy the required OBD catalyst monitor.

To use it requires a lot of data points and math. An EWMA value is calculated after multiple onboard tests using very tight fuel control perturbations under special conditions. We can't do that as technicians.

Verifying a faulty catalyst is easy. Test for those things that the ECM cannot, make sure there isn't a software update to correct for a false fail, and then trust the onboard monitor. It really is that simple.

There will always be anomalies, but we fool ourselves when we think we are better than the onboard test.

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