Milanski Posted June 22, 2019 Share Posted June 22, 2019 Is the downstream sensor (after cat convertor) used in fueling control? I have installed a AFR meter to mine and engine seems to run smooth still, so I am not sure what they actually do in the ECU. 5.4L V8 HADCH or HADCG. Quote Link to comment Share on other sites More sharing options...
Darryl@pcmtec Posted June 22, 2019 Share Posted June 22, 2019 It is used to help to keep the catalyst within its correct window and hence compensate for aged front O2 sensors. Ford calls the logic FAOSC to do this and can be controlled in the calibration. Quote Link to comment Share on other sites More sharing options...
Milanski Posted June 23, 2019 Author Share Posted June 23, 2019 Thanks Daryl. Can the function be turned off and where? I have a wideband in the downstream for tuning. Quote Link to comment Share on other sites More sharing options...
Milanski Posted June 23, 2019 Author Share Posted June 23, 2019 Found it "FAOSC" filter. Quote Link to comment Share on other sites More sharing options...
Darryl@pcmtec Posted June 23, 2019 Share Posted June 23, 2019 And you can also turn the rear O2 sensor off by setting auF0011 to 0: Do not change auF0010 to 1 on a V8. Not sure why Ford does this but it uses the number of O2 sensors on a V8 to run certain V8 code. Quote Link to comment Share on other sites More sharing options...
Milanski Posted June 23, 2019 Author Share Posted June 23, 2019 8 hours ago, Darryl@pcmtec said: And you can also turn the rear O2 sensor off by setting auF0011 to 0: Do not change auF0010 to 1 on a V8. Not sure why Ford does this but it uses the number of O2 sensors on a V8 to run certain V8 code. Excellent - works Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted June 24, 2019 Share Posted June 24, 2019 If you are curious have a read of the various patents Ford have filed over the years regarding downstream O2 sensors. They go into quite a bit of detail. https://patents.google.com/patent/US6879906 As Darryl said above the main use of the rear o2 sensor is to "age" the front sensor and measure the voltage shift over time which can then be used to correct for an old sensor which would otherwise need to be replaced. This system completely falls apart when you change the catalytic converter efficiency (eg high flow cat or huge exhaust) so you will not be going backwards by disabling it if you are no longer running the factory exhaust and cat. Chances are your NOx and CO are completely out the window from the factory specs once you do any modifications. 1 Quote Link to comment Share on other sites More sharing options...
Milanski Posted June 24, 2019 Author Share Posted June 24, 2019 Ford spend so much time and money to work out if a $100 part is ageing? Better of spending that money making something else work better. Just put it down to a replace at 100k in warranty book. Better still put in a wideband! Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted June 24, 2019 Share Posted June 24, 2019 12 minutes ago, Milanski said: Ford spend so much time and money to work out if a $100 part is ageing? Better of spending that money making something else work better. Just put it down to a replace at 100k in warranty book. Better still put in a wideband! Think about it. 2 programmers for 1 year is maybe 250k How many F150s are sold each year? 1.1 million. How many other Fords that use this software? Maybe 4 million? How long does an O2 sensor last without the downstream sensor aging it? Lets say 2 years, how long does it last with the aging software? Maybe 5 years? $100 x 4 million = $400 million in replacement O2 sensors. Return on investment? Absolute no brainer. It isn't even a question of you can spend the money on something else, with that kind of ROI you could just borrow the money for the programmers up front and pay interest on it and still come out in front. It is cumulative as well, the FAOSC software was written in the early 2000s and still used to day, its probably saved them over a billion dollars since inception. They don't just do this with O2 sensors they do it with everything. They have a complicated airflow model that models the cooling affect of the fans on the engine in modern vehicles, this might take someone 6 months to model in tensorflow, then a programmer a few months to program it. But if the result is the fan turns on 10% less often, this means they can change the service interval for replacing the fan by maybe 10%, how much does this save them? Even if its a $5 part it is very easy to see the economics in it. This might also help explain why the software in a modern Ford is so damn complicated. There is usually a good reason behind everything you see, and that "good" reason is more dollars for the bean counters. 1 Quote Link to comment Share on other sites More sharing options...
Milanski Posted June 24, 2019 Author Share Posted June 24, 2019 There are plenty of examples where cars run on ONE O2 sensor - i.e. my toyota has one and seems to go just fine. I do agree with ROI and getting 12 years out of my sensors is pretty damn good. Also having worked with hazardous areas for a decade, no matter what code is put into a ECU - it will still be an approximation - you need to calibrate the sensors at regular intervals. This being said, its a good point - time to replace my O2 sensors. Quote Link to comment Share on other sites More sharing options...
Gabbo32 Posted July 1, 2019 Share Posted July 1, 2019 On 6/24/2019 at 12:02 PM, Roland@pcmtec said: If you are curious have a read of the various patents Ford have filed over the years regarding downstream O2 sensors. They go into quite a bit of detail. https://patents.google.com/patent/US6879906 Those Ford patents are awesome. So helpful to understand the theory from Ford's perspective. 1 Quote Link to comment Share on other sites More sharing options...
Mick Posted November 4, 2019 Share Posted November 4, 2019 Do you know what FAOSC actually stands for? Quote Link to comment Share on other sites More sharing options...
Roland@pcmtec Posted November 5, 2019 Share Posted November 5, 2019 FORD Acronyms booklet.pdf Fore/aft oxygen sensor control. Loads of Ford acronyms in this PDF. I found it on google. It is very old from the late 90s. 1 Quote Link to comment Share on other sites More sharing options...
Mick Posted November 7, 2019 Share Posted November 7, 2019 Thank you Quote Link to comment Share on other sites More sharing options...
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