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Old 07-22-2021, 07:50 PM   #211
73TORANA!
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Originally Posted by steve99 View Post
The values in fuel tables is the values your asking for, the afr value is the measured value from the afr sensor its never going to be exact especially atfluctuating rpm and loads. at light loads light throttle the ecu will use long and sgort term fuel trims to try to match those up


If iam is lass than 1 the fueling compensation table comes into play and may slightly richen fueling depending on value s in that table
Thx Steve for your reply, I think I may have poorly worded my question. there is no IAM drop and yes I understand you will get a richer mix with an IAM drop. My eng load is around .5 in cruise @ 2k rpm so I was trying to work out from the CL fuel correction table what the commanded AFR should be as apposed to the commanded AFR that im seeing on my OFT as it not what I thought it should be, forget actual AFR at this stage as im just trying to work out the how it is calculated from the tables I can see. I have read that the #2 O2 sensor in a UEL cattless header can cause the commanded AFR in C/L to drop / fluctuate and should have its table set to zero ??? thoughts. Cheers.
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Old 07-23-2021, 08:07 AM   #212
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Thx Steve for your reply, I think I may have poorly worded my question. there is no IAM drop and yes I understand you will get a richer mix with an IAM drop. My eng load is around .5 in cruise @ 2k rpm so I was trying to work out from the CL fuel correction table what the commanded AFR should be as apposed to the commanded AFR that im seeing on my OFT as it not what I thought it should be, forget actual AFR at this stage as im just trying to work out the how it is calculated from the tables I can see. I have read that the #2 O2 sensor in a UEL cattless header can cause the commanded AFR in C/L to drop / fluctuate and should have its table set to zero ??? thoughts. Cheers.

Ok


OFT in general logs commanded afr about 0.2 afr points leaner than the correct value, jist a logging error i believe


Also in cruise mode the ecu also looks at the rear 02 senspr and apples a coreection to afr known as #AF3 correction, this is not reflected in commaned afr logged parameter.


You need to log #AF3 not sure if oft logs that
This can cause measured afr feom the front wideband 02 to drift from the commanded afr.


The rear 02 is only narrowband and only used for cat monitoring and cruise fueling correction.


Generally I zero out #af3 coreection in tune and many headers put the rear 02 in a long tube so fhe rear 02 sensor doesnt read correctly.
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Old 07-24-2021, 05:43 AM   #213
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Thanks Steve,
I set the #AF3 tables in rom raider to "0" and went for a drive. It made a big difference. The Command AFR in C/L cruise is 14.89 - .2 logging error is 14.69 and the actual AFR is 14.58 with minor fluctuations as it was with the factory headers. The actual AFR reading is a lot more stable as well. Thanks for your help in clearing this up for me. I did feel the second O2 was for catt efficiency, its makes sense. I recon setting #AF3 to zero will most probably also help with LTFT learning. Cheers
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Old 07-24-2021, 09:50 AM   #214
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Thanks Steve,
I set the #AF3 tables in rom raider to "0" and went for a drive. It made a big difference. The Command AFR in C/L cruise is 14.89 - .2 logging error is 14.69 and the actual AFR is 14.58 with minor fluctuations as it was with the factory headers. The actual AFR reading is a lot more stable as well. Thanks for your help in clearing this up for me. I did feel the second O2 was for catt efficiency, its makes sense. I recon setting #AF3 to zero will most probably also help with LTFT learning. Cheers
This is interesting. But does it actually affect commanded AFR though, as @steve99 mentioned that it shouldn't.
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Also in cruise mode the ecu also looks at the rear 02 senspr and apples a coreection to afr known as #AF3 correction, this is not reflected in commaned afr logged parameter.
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Old 07-24-2021, 09:08 PM   #215
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This is interesting. But does it actually affect commanded AFR though, as @steve99 mentioned that it shouldn't.

Its a bit confusing


the #af3 correction does appear to make a difference to the actual target afr in cruise mode. However sometimes you dont see it effect the logged commanded afr paramter. I suspect some systems log commanded afr parameter before the #af3 is added to it, and some dont.
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Old 07-24-2021, 09:45 PM   #216
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Quote: "This is interesting. But does it actually affect commanded AFR though, as @steve99 mentioned that it shouldn't"

In my case as mentioned it did affect the commanded AFR.
The commanded AFR that I am seeing now follows closely what I can calculate by subtracting the C/L fueling correction table from 14.7 It logs it at 0.2 higher as Steve mentioned and does seem to be a bit hit and miss with its refresh rate. BUT the actual AFR in C/L now also follows the C/L fuel correction table more accurately although 0.2 AFR lower as I believe the OFT logs the AFR at actual - 0.2 lower. It may also be my imagination the car feels much smother maybe because its not chasing its tale ??
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Old 07-24-2021, 11:06 PM   #217
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Its a bit confusing


the #af3 correction does appear to make a difference to the actual target afr in cruise mode. However sometimes you dont see it effect the logged commanded afr paramter. I suspect some systems log commanded afr parameter before the #af3 is added to it, and some dont.
That was my initial guess as well, there are likely two commanded AFR parameters pre and post AF#3.
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Quote: "This is interesting. But does it actually affect commanded AFR though, as @steve99 mentioned that it shouldn't"

In my case as mentioned it did affect the commanded AFR.
The commanded AFR that I am seeing now follows closely what I can calculate by subtracting the C/L fueling correction table from 14.7 It logs it at 0.2 higher as Steve mentioned and does seem to be a bit hit and miss with its refresh rate. BUT the actual AFR in C/L now also follows the C/L fuel correction table more accurately although 0.2 AFR lower as I believe the OFT logs the AFR at actual - 0.2 lower. It may also be my imagination the car feels much smother maybe because its not chasing its tale ??
I have not tried this yet, but I usually log AFRs via OBD2 as well - my take is that the commanded AFR shown in the OBD2 standard PID should be post-AF#3 since that value makes more sense when doing a diagnosis.
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Old 07-26-2021, 05:55 AM   #218
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No FBKC at all, and loads are well under the load limits. Here's the log if it helps illustrate things:

https://datazap.me/u/compelica/knock...?log=0&data=20



too much PI on high rpm
reduce it and put more DI to help , or just reduce the advance timing


i would also scale a bit better the maf scaling where afr is getting leaner on mid high rpm so it helps to not trigger the knocks
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Old 07-26-2021, 06:23 AM   #219
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too much PI on high rpm
reduce it and put more DI to help , or just reduce the advance timing


i would also scale a bit better the maf scaling where afr is getting leaner on mid high rpm so it helps to not trigger the knocks
Thanks @tomm.brz for the insight, I was asking on the low RPM high load situation and whether there it is possible to advance past MBT.
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Old 07-28-2021, 07:13 AM   #220
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well don t rise too much the timings in low load zone, no need to
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Old 07-29-2021, 05:04 AM   #221
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Thanks Steve,
I set the #AF3 tables in rom raider to "0" and went for a drive. It made a big difference. The Command AFR in C/L cruise is 14.89 - .2 logging error is 14.69 and the actual AFR is 14.58 with minor fluctuations as it was with the factory headers. The actual AFR reading is a lot more stable as well. Thanks for your help in clearing this up for me. I did feel the second O2 was for catt efficiency, its makes sense. I recon setting #AF3 to zero will most probably also help with LTFT learning. Cheers
@73TORANA! which AF #3 tables did you specifically alter?
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