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Discussion Starter #1
Does anyone know what the highs/lows/avg is for the upstream (wideband) O2 and the downstream O2 is? MAF values? Does anyone have a datalog for these they can send me or post so I can compare?
 

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Ghost, I can assume you mean for a Redline? The Redlines' 2.0 turbo has a wide band O2 for the upstream sensor and the 2.4 has a narrow band so their readings will be different. However, most people log the Wide Band O2s as AFR rather than a raw return because AFR is what really matters. Narrow Bands can't really get an AFR reading unless it's right around 14.7.

The downstream O2 really isn't all that important. All it's doing is checking to see if the Cat is working. No engine managment comes of that so I'm not sure what the need for a reading is for. Though, you are asking for a range. MAF values will be different for 2.4 vs 2.0 as well as the turbo pulls in a lot more air. I think the MAFs are the same, but your average between the two setups won't be.
 

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Discussion Starter #3
Thanks Robo. I'm having a commanded AFR issue on my 2.0L. It seems to be stuck at 13.79 or 27.58 (off the gas!). And I'm thinking maybe it's the O2 sensor...but I'm not 100% and dont want to spend $125 on a part that might not fix the issue.
 

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Well wait, the Commanded AFR is a setting in your ECM. This is the target AFR the ECM is trying to hit. This is the number it compares against the Actual AFR, what the O2 is reporting as coming out of the exhaust, and if they don't match, the ECM adjusts fueling to try and make them match. This value isn't affected by the O2 at all.

For Port Injection, a targeted AFR of 14.7 is normal. 13.79 would be rich, but on the 2.0 this may be spot on. Mind you, this is under idle or cruise situations. Heavy load moments like accelerating or going up hill should display a richer Commanded AFR (2.4 is about 11-12:1 and 2.0 is 10:1 IIRC) and off throttle will also show a leaner AFR because it's shutting down the injectors to help slow the car using engine compression...so 27.58:1 doesn't sound as bad as you think off throttle. Again, this may be different with the direct injected 2.0, but this is what I see in my port injected 2.4.
 

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Discussion Starter #5
So I dont know how my commanded AFR would have changed. I haven't had my car anywhere for it to be changed. Prior logs show it commanding 14.7 at idle and cruising....as well as 29.4 when off the gas. How could commanded have changed? What would have caused it to change? Learning? That's why I thought my wideband O2 sensor might be bad.
 

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You can send me the log (however, I'm not as familiar with the tunes on the LNF and you'd be better finding someone more familiar with them to look at it...) but you can tell if it's a learning thing by resetting your ECM and see if it reverts to what it was before. I know commanded AFR changes based on engine state (Meaning a given AFR for an engine state based on RPM, Coolant Temp, Vehicle Speed, Engine Load, Throttle position, throttle pedal position, etc.) but I didn't think it would change based on O2 readings...but because you have a Wide Band O2 as OEM, it could. I've only used ECMs that rely just on a Narrow Band O2 for fueling which can't do WOT adjustments.
 
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