I was reviewing some INPA screen shots from the BMW and I noticed that the Lambda screen showed what looked to me to be an anomaly.
Bank 1 before catalyst: .82
Bank 1 after catalyst: .71
Bank 2 before catalyst: .12
Bank 2 after catalyst: .72
So, while the "after catalyst" numbers are very similar, the "before catalyst" numbers are not. What's considered "normal" here and what could explain these particular numbers?
Car is 2003 BMW 530i with 171k miles and no SES light.
Thanks!
In reply to 1988RedT2 :
14.7:1 AFR = 1.0 Lambda Lower than 1.0 is rich, above 1.0 is lean. Back 2 is rich and the catalyst is cleaning it up.
Probably.
AFR tends to dither back and forth across stoich at idle. So it's normal to see the O2 readings show rich-lean-rich-lean as the ECU balances the engine. You might have snapped those readings at different points. I think the cats act as a buffer but I'm not as solid on that.
More valuable would be short term and long term trim numbers if you're trying to determine if something is amiss as opposed to hunting down a specific behavior.
I'm very new to INPA, but I think the range is from 0 to 1 with a lot of variation while the engine is running. I'm thinking these numbers aren't particularly meaningful as a snapshot. Still looking for info.
Are those lambda numbers (AFR/AFR-stoich), or are they the raw voltage from the sensor?
In reply to codrus (Forum Supporter) :
Well, the number is identified as Lambda, but the units are indicated by "V", so volts. I dunno? Values seem to be in the range of zero to one.
In reply to codrus (Forum Supporter) :
I was assuming raw voltage.
1988RedT2 said:In reply to codrus (Forum Supporter) :
Well, the number is identified as Lambda, but the units are indicated by "V", so volts. I dunno? Values seem to be in the range of zero to one.
Yeah, the numbers are probably just voltage. For a narrowband sensor that ranges between 0.1 (rich) and 0.9 (lean), with stoich being in the middle. It doesn't provide much more granularity than that, which is why the computer dithers it back and forth across that threshold like Keith mentioned.
I agree that a snapshot of the data isn't very useful, you need to look at it over time. Some scan tools can generate a graph of the value as it changes, which is the best way to look at it.
You'll need to log in to post.
