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Catalytic Converter impact on Lambda

Understanding AFR

Discussion and questions related to the course Understand AFR


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What is the impact of the lambda reading if installed 36 inches down exhaust from the catalytic converter? Would it cause the lambda value to lean or rich? I have a reading of lambda 1.5, which obviously worries me! Thank you ahead of time. David

You probably have an exhaust leak, miss or failed sensor unless it is compression ignition. It may make a modest difference to transient readings if you are close to lambda 1 on the sweep but under lean cruise or high load and difference is likely to be insignificant relative to wideband accuracy unless you have a very heat tolerant engine which doesn't run far rich i stoic at high load and makes a lot of NOx to balance out CO on the catylist.

TLDR only likely to make marginal difference to transients away from lambda 1 cruise.

From our own testing the catalytic convertor has almost no real impact on the AFR reading. Your problem definitely is somewhere else.