LTFT-> PE
12-24-2006, 05:18 PM
#13
Originally Posted by KySilverado
I am aware of this. The point of this post. I had been OLSD tuning for weeks. I have now enabled CL STFT's and LTFT's. In OLSD I have gotten VE pretty darned close, commanded AFR% error within 3-4% and now when I turned CL back on it has driven my PE fueling very rich. In open loop I am within 2% of commanded. With closed loop enabled my PE is 9% rich. WHY? It appears it is bringing LTFT correction into PE which I don't understand.
Personnaly I think the only real way to fix the problem is have a ve table for each bank or cylinder or the real fix is to find out why one side is using more fuel than the other(which could be just the inherent mechanical design of the engine). Ive tried everything to fix mine from 02's, injectors, inj cleaning, rewelding the entire exhaust etc... the only conclusion Ive come to is the infamous #7 leaning, but its circumstantial evidence.
12-24-2006, 07:12 PM
#14
No offense taken, or given I hope. Sometimes the frustration with my inabilities at tuning or communicating my questions bleed through to my posts. 
I agree that differences in 02 sensors and fueling from bank to bank can be the issue I am having. I would have phrased it differently though. Its not the difference in 02 readings I see during PE that is the issue. I think these are live AFR 02 readings based upon fueling generated from fueling errors (LTFT's) that are stored in the LTFT and FTC the last time they were calculated for this FTC (fuel trim cell) during the STFT cycle. Please correct me if I'm wrong. I need to understand it.
So basically you tune one bank (in my case) of the engine with a WB. Get the VE right for that bank. Enable closed loop. Then the other bank is lean, so the fuel trims will over time adjust fueling up based upon the average fueling requirements for both banks. LTFT's go positive, when they were spot on for the OL tuning of the one bank. You enter PE and it adds this fueling and drives your open loop PE AFR rich.
This is assuming that any LTFT + or - will be carried into/affect your PE fueling. Which I didn't know would. Someone please confirm this. If you are carrying a +LTFT say in FTC 15 and then you enter PE in this same FTC it will adjust PE fueling by the % of LTFT? Would it also remove fueling if the LTFT is negative.
This could explain some of the strange KR I have been seeing? Possibly B2 being lean. The KR is improving a little it appears with the short time I've had Fuel Trims on.
Maybe I need to put my stock O2 back in, put the WB downstream, post cats, and tune for both banks. Making allowances in WOT AFR for being post cat and start all over with my tuning?
Added a log file of what I am seeing, beats the screen shot.
I agree that differences in 02 sensors and fueling from bank to bank can be the issue I am having. I would have phrased it differently though. Its not the difference in 02 readings I see during PE that is the issue. I think these are live AFR 02 readings based upon fueling generated from fueling errors (LTFT's) that are stored in the LTFT and FTC the last time they were calculated for this FTC (fuel trim cell) during the STFT cycle. Please correct me if I'm wrong. I need to understand it.
So basically you tune one bank (in my case) of the engine with a WB. Get the VE right for that bank. Enable closed loop. Then the other bank is lean, so the fuel trims will over time adjust fueling up based upon the average fueling requirements for both banks. LTFT's go positive, when they were spot on for the OL tuning of the one bank. You enter PE and it adds this fueling and drives your open loop PE AFR rich.
This is assuming that any LTFT + or - will be carried into/affect your PE fueling. Which I didn't know would. Someone please confirm this. If you are carrying a +LTFT say in FTC 15 and then you enter PE in this same FTC it will adjust PE fueling by the % of LTFT? Would it also remove fueling if the LTFT is negative.
This could explain some of the strange KR I have been seeing? Possibly B2 being lean. The KR is improving a little it appears with the short time I've had Fuel Trims on.
Maybe I need to put my stock O2 back in, put the WB downstream, post cats, and tune for both banks. Making allowances in WOT AFR for being post cat and start all over with my tuning?
Added a log file of what I am seeing, beats the screen shot.
Last edited by KySilverado; 12-24-2006 at 07:53 PM.
12-24-2006, 09:34 PM
#15
Originally Posted by KySilverado
I agree that differences in 02 sensors and fueling from bank to bank can be the issue I am having. I would have phrased it differently though. Its not the difference in 02 readings I see during PE that is the issue. I think these are live AFR 02 readings based upon fueling generated from fueling errors (LTFT's) that are stored in the LTFT and FTC the last time they were calculated for this FTC (fuel trim cell) during the STFT cycle. Please correct me if I'm wrong. I need to understand it.
So basically you tune one bank (in my case) of the engine with a WB. Get the VE right for that bank. Enable closed loop. Then the other bank is lean, so the fuel trims will over time adjust fueling up based upon the average fueling requirements for both banks. LTFT's go positive, when they were spot on for the OL tuning of the one bank. You enter PE and it adds this fueling and drives your open loop PE AFR rich.
This is assuming that any LTFT + or - will be carried into/affect your PE fueling. Which I didn't know would. Someone please confirm this. If you are carrying a +LTFT say in FTC 15 and then you enter PE in this same FTC it will adjust PE fueling by the % of LTFT? Would it also remove fueling if the LTFT is negative.
This could explain some of the strange KR I have been seeing? Possibly B2 being lean. The KR is improving a little it appears with the short time I've had Fuel Trims on.
Maybe I need to put my stock O2 back in, put the WB downstream, post cats, and tune for both banks. Making allowances in WOT AFR for being post cat and start all over with my tuning?
Added a log file of what I am seeing, beats the screen shot.
So basically you tune one bank (in my case) of the engine with a WB. Get the VE right for that bank. Enable closed loop. Then the other bank is lean, so the fuel trims will over time adjust fueling up based upon the average fueling requirements for both banks. LTFT's go positive, when they were spot on for the OL tuning of the one bank. You enter PE and it adds this fueling and drives your open loop PE AFR rich.
This is assuming that any LTFT + or - will be carried into/affect your PE fueling. Which I didn't know would. Someone please confirm this. If you are carrying a +LTFT say in FTC 15 and then you enter PE in this same FTC it will adjust PE fueling by the % of LTFT? Would it also remove fueling if the LTFT is negative.
This could explain some of the strange KR I have been seeing? Possibly B2 being lean. The KR is improving a little it appears with the short time I've had Fuel Trims on.
Maybe I need to put my stock O2 back in, put the WB downstream, post cats, and tune for both banks. Making allowances in WOT AFR for being post cat and start all over with my tuning?
Added a log file of what I am seeing, beats the screen shot.
Try this to test if one side is leaner than the other.
1. clear trims
2. get a log of wot
3. clear trims again
4. swap wideband to other side
5. get another log of wot
6. compare
Keep the WB in front of the cats on both sides.
Once you determine the leaner bank you should tune for that side and just keep the Ltft's disabled but run off the stft's(do this because you cant fix the fueling discrepancy between banks) but at least you know your safe.
Personnaly I wouldnt run that engine in OLSD ever again, keep the stft's and keep the back cylinders togethor.
If anyone has been able to fix the 02 WOT discrepancy Id really like to hear about it.
12-25-2006, 09:02 AM
#16
Hey thanks for the info. This dang tuning is getting more complicated with every turn. Every question opens up dozens more.
You are right. I need to put the WB in the other bank and see where it is, tune for the leanest bank. I'm not beyond installing a second WB permanently for something this important.
I need to study the narrowband signal from the WB more closely. When I was using 2 stock o2's the mv spread wasn't so much. Both WB's I've had in emulate the NB signal about the same. About 750mv for 11.8 and the stock narrowband reports about 920mv which doesn't seem out of line. What I wasn't aware of is the PCM sees this as problem in PE and modifies fueling because of it. The major problem with this is the primary reason I went with a 2bar os. To get PE/WOT fueling correct and under control. If it means I run STFT's only no biggie I supose.
You are right. I need to put the WB in the other bank and see where it is, tune for the leanest bank. I'm not beyond installing a second WB permanently for something this important.
I need to study the narrowband signal from the WB more closely. When I was using 2 stock o2's the mv spread wasn't so much. Both WB's I've had in emulate the NB signal about the same. About 750mv for 11.8 and the stock narrowband reports about 920mv which doesn't seem out of line. What I wasn't aware of is the PCM sees this as problem in PE and modifies fueling because of it. The major problem with this is the primary reason I went with a 2bar os. To get PE/WOT fueling correct and under control. If it means I run STFT's only no biggie I supose.
12-25-2006, 11:16 AM
#17
Originally Posted by KySilverado
Hey thanks for the info. This dang tuning is getting more complicated with every turn. Every question opens up dozens more.
You are right. I need to put the WB in the other bank and see where it is, tune for the leanest bank. I'm not beyond installing a second WB permanently for something this important.
I need to study the narrowband signal from the WB more closely. When I was using 2 stock o2's the mv spread wasn't so much. Both WB's I've had in emulate the NB signal about the same. About 750mv for 11.8 and the stock narrowband reports about 920mv which doesn't seem out of line. What I wasn't aware of is the PCM sees this as problem in PE and modifies fueling because of it. The major problem with this is the primary reason I went with a 2bar os. To get PE/WOT fueling correct and under control. If it means I run STFT's only no biggie I supose.
You are right. I need to put the WB in the other bank and see where it is, tune for the leanest bank. I'm not beyond installing a second WB permanently for something this important.
I need to study the narrowband signal from the WB more closely. When I was using 2 stock o2's the mv spread wasn't so much. Both WB's I've had in emulate the NB signal about the same. About 750mv for 11.8 and the stock narrowband reports about 920mv which doesn't seem out of line. What I wasn't aware of is the PCM sees this as problem in PE and modifies fueling because of it. The major problem with this is the primary reason I went with a 2bar os. To get PE/WOT fueling correct and under control. If it means I run STFT's only no biggie I supose.
Id like to hear the results if you put one on each side.
