Why is AFR off so much from bank to bank with dual wideband?
10-05-2008, 08:10 AM
#1
Why is AFR off so much from bank to bank with dual wideband? I ws just wondering if anyone is running a dual wideband and if they are if they've noticed how different their readings are from side ot side. Mine idling is normal within .1 afr and cruising .1 afr, WOT .1 afr but sometimes ill see it fluctuating or jumping under all forms of throttle to as much at 1 afr. any ideas what it might be?
10-05-2008, 11:21 AM
#4
The engine is a 2000 LS1 but im running a carb setup so no computer i just have a Fast Dual wideband 02 monitor. I can see the left bank running at 13.2 and say the right bank will go to 12.2 sometimes. I'm sure i'm just seeing things that dont really matter. The intake is a dual plane so i doubt it would be anything in the carb i'm going to pull the plugs and re-gap them as i have them at .055 right now and they are tr6 plugs which should be like .035 or something. I cant imagine it being anything in my valvetrain.
10-05-2008, 04:00 PM
#6
Well i have the option to average them together in the display which is what i normally do but i was going to use the secondary sensor to diagnose mechanical problems. Its normal most of the time so i am just going to assume its a sensor error every now and then, perhaps an exhaust leak where the band clamp bolts to the headers or something. I'm not sure. I dont think its really a problem though just wondering if anyone else experienced it.
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01-29-2010, 07:22 PM
#10
I run dual WB and I saw the same thing with my original 346 cammed engine and with my new 408 LS3 cammed engine. Two completly diferent engines, one old and one new, both did the same thing, both had different injectors and exhaust, the only thing that was the same was the coils and PCM. I did change the cam in the 408 resently and now they seam to be very close. The new cam is a little smaller then the cams I use to run. maybe it is a cam thing. I did look for the cause for two years and I never found it. the only thing that made the banks more ballance was going to this new cam. I never saw anything negative from this situation. It also might just be the diference between the WB sensors or their location as compared to the other, or the calibration of the two.
01-30-2010, 01:16 AM
#11
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I wouldn't be surprised,
If they all do this. I've seen this happen on all the cars I've logged and put it down to the fuel delivery design on LS engines with the returnless system.
Maybe the ppl that have modified their engines to run with a return system don't have this?
It's not really enough to worry about anyway. Sometimes we maybe tend to see into things too much when in fact the engine is running just fine.
If they all do this. I've seen this happen on all the cars I've logged and put it down to the fuel delivery design on LS engines with the returnless system.
Maybe the ppl that have modified their engines to run with a return system don't have this?
It's not really enough to worry about anyway. Sometimes we maybe tend to see into things too much when in fact the engine is running just fine.
01-30-2010, 08:07 AM
#12
I do have a return fuel system too. But I put it on at the end of the summer and I can not remember if the difference between the banks evened out after I upgraded to a return fuel system or the cam. Now I will not be able to sleep at night trying to remember what happened!!! 
01-30-2010, 10:44 AM
#14
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It's normal for them to differ some from bank to bank, there are four individual cylinders in each bank that each sensor is averaging. Some cylinders may be richer or leaner than others at times. Even the stock narrow bands are off by a few when logging, I have never seems them dead on at all times.
10-16-2015, 10:50 AM
#16
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Sorry for the old thread resurrection, but I cannot seem to find much info on an acceptable difference between banks.
Thought it might be good to bring this one back to see if it might stir up some more opinions.
Thank guys!
Thought it might be good to bring this one back to see if it might stir up some more opinions.
Thank guys!
10-16-2015, 12:54 PM
#17
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I have two widebands. With my 19* cam, at idle the two are often 1.0 AFR different.
At high throttle only about 0.2 AFR different.
A much leaner side might indicate you have a vacuum leak on that side.
At high throttle only about 0.2 AFR different.
A much leaner side might indicate you have a vacuum leak on that side.
10-16-2015, 03:21 PM
#18
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I've been having some discussion with my speedshop on my readings and he has been telling me it's no big deal. However, I'm a particular kinda guy so I have been trying to determine what is an acceptable diff.
These readings in the attachment were with two different brands of WB units in each bank, however I have since replaced one of the WB units, so now there are two matching Innovative MTX-L units.
Unfortunately other issue have prevented me from gathering too much usable WOT data with the matching WBs.
The previous WB setup was an old PLX WB unit and a new MTX-L WB unit, but I was tending to believe what they said, because they tracked alot closer in the previous engine, at least for awhile. The factory HEGOs also seemed to agree with what the WBs were reading, particularly when comparing the STFTs in normal driving.
Shop was saying this little difference between banks could be a coil, the WBs being off, or maybe an injector or two was slightly off; and that the STFTs could be my relatively new factory HEGOs.
So I replaced all coils, plugs, HEGOs, and plugs and will check the imbalance again. If the imbalance remains, my next step will be to swap injectors from one bank to another and see if the readings shift.
What I really need to know is at one point I should be concerned??? What diff is acceptable?
These readings in the attachment were with two different brands of WB units in each bank, however I have since replaced one of the WB units, so now there are two matching Innovative MTX-L units.
Unfortunately other issue have prevented me from gathering too much usable WOT data with the matching WBs.
The previous WB setup was an old PLX WB unit and a new MTX-L WB unit, but I was tending to believe what they said, because they tracked alot closer in the previous engine, at least for awhile. The factory HEGOs also seemed to agree with what the WBs were reading, particularly when comparing the STFTs in normal driving.
Shop was saying this little difference between banks could be a coil, the WBs being off, or maybe an injector or two was slightly off; and that the STFTs could be my relatively new factory HEGOs.
So I replaced all coils, plugs, HEGOs, and plugs and will check the imbalance again. If the imbalance remains, my next step will be to swap injectors from one bank to another and see if the readings shift.
What I really need to know is at one point I should be concerned??? What diff is acceptable?
10-16-2015, 04:18 PM
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The tuner at the shop has disabled the adaptive fueling. I know the LTFTs never leave "1" and it is my understanding that this was due to disabling the adaptive fueling.
I am under the impression that the car runs in closed loop using STFTs until WOT; I see the STFTs constantly trying to move towards 1 at all times and the WBs trying to stay stoich-ish. The STFTs do seem to move around pretty wildly. At idle they might be .90-.110 then at light cruise they might get to .80 -.100; moderate pull might get .70-.90. But there is a pretty consistent delta in the STFTs bank to bank much of the time.
Might be a good time to admit it... this is one of the infernal 4.6 Ford DOHC Mod Motors in a Mercury Marauder. I do, however, now wish that I had given alot more serious thought to swapping to an LS motor. Which it really hurts to admit...
My speed shop is run by an LS guy as well.
I posted here because this was one of the better threads I could find on the subject and figured bank to bank AFR delta thresholds would be pretty much universal.
I hope nobody is offended by my fordness
I am under the impression that the car runs in closed loop using STFTs until WOT; I see the STFTs constantly trying to move towards 1 at all times and the WBs trying to stay stoich-ish. The STFTs do seem to move around pretty wildly. At idle they might be .90-.110 then at light cruise they might get to .80 -.100; moderate pull might get .70-.90. But there is a pretty consistent delta in the STFTs bank to bank much of the time.
Might be a good time to admit it... this is one of the infernal 4.6 Ford DOHC Mod Motors in a Mercury Marauder. I do, however, now wish that I had given alot more serious thought to swapping to an LS motor. Which it really hurts to admit...
My speed shop is run by an LS guy as well.
I posted here because this was one of the better threads I could find on the subject and figured bank to bank AFR delta thresholds would be pretty much universal.
I hope nobody is offended by my fordness