Lambda question again...
The user defined formula for the NGK AFX is volts/10.42+ .62 to have the scanner read in lambda. No matter what fuel you have in the tank.
I'm not sure what NGK wideband you are referring to.
I think you guys are confusing the tune stoich vs the scanner.
I'm not sure what NGK wideband you are referring to.
I think you guys are confusing the tune stoich vs the scanner.
That's right Ron. Although doesn't the new NGK show lambda on the output LED? The old one just shows AFR around gasoline, which is why I was giving the formulas for AFR and saying to ignore what the actual output on the LED says.
If you set the scanner to Lambda it doesn't matter and you should totally ignore the LED on the old NGK. However, if you use the AFR formula, you just need to make sure the stoich setting in the tune and the AFR formula match.
If you set the scanner to Lambda it doesn't matter and you should totally ignore the LED on the old NGK. However, if you use the AFR formula, you just need to make sure the stoich setting in the tune and the AFR formula match.
Joined: Aug 2007
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From: Turnin' Wrenches Infractions: 005
Since the only fuel we see around here is likely e5-e10 I did what he was wanting to do at the start of the thread. I tune everything for e10 but I tune in afr. So because the ngk will still still read 14.6 for my e10 ratio of 14.1 I made the change in the voltage offset when inputting the wideband into hptuners. Meaning e10 will show 14.6 stoich on the ngk but hptuners will be accurate to actual afr and show me 14.1 which is what I'm shooting for. Just made more sense in my head to me. We have NO non-e gas here so might as well compensate for it. By changing the offset it permanently makes hptuners read for e10.
Thread Starter
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From: Hurley, VA
My wideband is a 96604 it only displays afr but I was always thought with lambda you didn't have to change the stoich that no matter what fuel it was reading it would display 1.0 for the stoich of that fuel. I actually read on hptuners forum a guy say to tune in lambda and the only thing you had to change car to car would be the stoich in the tune. I'm confused again
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From: Ann Arbor, MI
Imagine the AFR gauge as an old style with a needle. I snap on a "Lambda" faceplate and the needle moves from .75 to 1.25 with 1.00 in the middle. Now I remove the faceplate and snap on a "E0 AFR" faceplate and the needle moves from 10.0 to 18.0 with 14.7 in the middle. Then I remove the faceplate and snap on a "E10 AFR" faceplate and the needle moves from 9.5 to 17.5 with 14.1 in the middle. In all cases the needle is accurate, the number we read from it just depends upon which faceplate we snapped in. Some people like Lambda, 01ssreda4 and others like the actual AFR for that particular gas, others just like the old fashion E0 values regardless of the actual gas. I prefer the latter because I learned tuning with an exhaust gas analyzer 30+ years ago when Sunoco 260 was leaded and cost 50 cents a gallon.
This is true. It's one of the times I could hear in my head that this wasn't probably coming out the way it was supposed to.
However, if you change the stoich fuel value in the editor (in the tune), I would strongly suggest changing the formula for AFR in the scanner. Otherwise, the scanner will be off.
If you tune in lambda and set lamdba in the scanner, it's a moot point. But almost all the tables in HPT are shown as equivalence ratios, so you're diving instead of multiplying by lambda anyway.
As I said, the book by Greg Banish actually explains how to tune optimally in lambda and provides you with ways to setup HPT to do it correctly.
I do it in AFR because that's what I was used to on my older setups.
However, if you change the stoich fuel value in the editor (in the tune), I would strongly suggest changing the formula for AFR in the scanner. Otherwise, the scanner will be off.
If you tune in lambda and set lamdba in the scanner, it's a moot point. But almost all the tables in HPT are shown as equivalence ratios, so you're diving instead of multiplying by lambda anyway.
As I said, the book by Greg Banish actually explains how to tune optimally in lambda and provides you with ways to setup HPT to do it correctly.
I do it in AFR because that's what I was used to on my older setups.
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From: Ann Arbor, MI
Some of the above comments have me slightly unsure about the meaning of the "Stoich AFR" value in the tune.
Please confirm whether my understanding is correct...
Let's assume open-loop steady state with a MAF.
The PCM knows how much air is coming in via the MAF in grams/second.
It knows how big the injectors are in grams/second.
Lets assume it wants to inject fuel for a stoich ratio (lambda =1).
To compute how much fuel is needed (i.e. the injector pulse width) it still
needs to know the "Stoich AFR" value.
Therefore if the MAF says there is 500 grams/second of air coming, it will
divide this number by the "Stoich AFR" value (e.g. 14.7) to determine how
much fuel to inject (e.g. 500 grams air /14.7= 34.0 grams fuel).
For small differences between e.g. E0 and E10, the tuning of the MAF (or VE table)
can easily compensate for a slightly "wrong" value of the "Stoich AFR".
However, if the gas changes between tank fulls from e.g. E10 to E5, the tune will
be off a bit.
In closed loop, the long term fuel trims can compensate for slightly
different tank fulls.
Is this correct or where am I wrong?
Please confirm whether my understanding is correct...
Let's assume open-loop steady state with a MAF.
The PCM knows how much air is coming in via the MAF in grams/second.
It knows how big the injectors are in grams/second.
Lets assume it wants to inject fuel for a stoich ratio (lambda =1).
To compute how much fuel is needed (i.e. the injector pulse width) it still
needs to know the "Stoich AFR" value.
Therefore if the MAF says there is 500 grams/second of air coming, it will
divide this number by the "Stoich AFR" value (e.g. 14.7) to determine how
much fuel to inject (e.g. 500 grams air /14.7= 34.0 grams fuel).
For small differences between e.g. E0 and E10, the tuning of the MAF (or VE table)
can easily compensate for a slightly "wrong" value of the "Stoich AFR".
However, if the gas changes between tank fulls from e.g. E10 to E5, the tune will
be off a bit.
In closed loop, the long term fuel trims can compensate for slightly
different tank fulls.
Is this correct or where am I wrong?
These discussions have confused me as well, I have EFI Live. So there is nothing to change in the sensor (the part that was confusing to me). You just need to change the tune software stoich value and the scan software stoich value so the adjustments made based on the scan logs are consistent with how the tune software reads them. Is this correct?
Thread Starter
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From: Hurley, VA
The way I'm understanding is the only thing that will actually change when you change the stoich of the wideband is what the screen will display (if the wideband will do that). Basically lambda 1 is stoich no matter what fuel you are using. Like my NGK AFRM, if I'm at lambda 1 the screen will show 14.7 even if I'm using E10 which actually has a stoich value of 14.14. So the way I'm looking at it, if I set the wideband to display lambda in hptuners 1.0 will be the stoich of whatever fuel i'm using, its just if you have the stoich in the tune set as 14.62 and the actual stoich of the fuel is 14.14, in closed loop you'll be off X amount. Somebody correct me if I'm wrong?
These discussions have confused me as well, I have EFI Live. So there is nothing to change in the sensor (the part that was confusing to me). You just need to change the tune software stoich value and the scan software stoich value so the adjustments made based on the scan logs are consistent with how the tune software reads them. Is this correct?
You need to set up your scanner to log Lambda and Lambda Error and forget about AFR and stop looking at your wideband's display.
You are confusing yourself by trying to tune with Lambda but still keep referring to AFR.
Tune with wideband and lambda in open loop for MAF and for VE.
Turn closed loop back on and set the Stoich Value to what you think it should be for the fuel you are using (14.1 for E10, 14.68 for E0, 9.8 for E85, 15 for C12, etc etc)
Measure your fuel trims, which are based on your stoich value that you set in the tune. If they are 5% rich or 10% lean or whatever they are, assuming you properly tuned the airflow tables in open loop, you can now adjust your stoich value to reflect a -3% fuel trim and live happily ever after.
You are confusing yourself by trying to tune with Lambda but still keep referring to AFR.
Tune with wideband and lambda in open loop for MAF and for VE.
Turn closed loop back on and set the Stoich Value to what you think it should be for the fuel you are using (14.1 for E10, 14.68 for E0, 9.8 for E85, 15 for C12, etc etc)
Measure your fuel trims, which are based on your stoich value that you set in the tune. If they are 5% rich or 10% lean or whatever they are, assuming you properly tuned the airflow tables in open loop, you can now adjust your stoich value to reflect a -3% fuel trim and live happily ever after.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
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From: So.Cal.
The stoich AFR in the tune and the stoich AFR assumed on the wideband are not coupled to each other...
the PCM uses stoich AFR to convert Lambda or EQR to fuelmass (see what Higgs Boson said to do to find stoich AFR);
the wideband reports lambda; the scantool can use stoich AFR to multiply wideband Lambda to report wideband AFR... but this AFR does not really matter, and is probably not correct; just simply use wideband Lambda for tuning;
for example the VE and MAF correction factor is: commanded_EQR x wideband_Lambda
( you don't even need to think about which should be the numerator/denominator )
the PCM uses stoich AFR to convert Lambda or EQR to fuelmass (see what Higgs Boson said to do to find stoich AFR);
the wideband reports lambda; the scantool can use stoich AFR to multiply wideband Lambda to report wideband AFR... but this AFR does not really matter, and is probably not correct; just simply use wideband Lambda for tuning;
for example the VE and MAF correction factor is: commanded_EQR x wideband_Lambda
( you don't even need to think about which should be the numerator/denominator )
Teching In
Joined: May 2012
Posts: 38
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From: Kingdom Of Bahrain
Question regarding the AFRM. I've used that tuning school formula and got the same number you guys have for the NTK AFRM, the display on the afrm was showing 15.0 afr the scanner would show something like 17-18 afr.... So I played with the scanner settings and ended up using (0.363 + 7.7) and the scanner showed me the same reading as the AFRM display. Is that the correct way to do it?
Note that i did check the grounding first before manipulating the numbers to read the same as the AFRM display.
Picture of the scanner table
https://app.box.com/s/wfqvub4c4zcxt7etmu5fv39wgkoh6gxf
A clip of the wideband and the scanner
https://app.box.com/s/yj3jn8ieiowgvo8kfoyhat1mif7idswr
Note that i did check the grounding first before manipulating the numbers to read the same as the AFRM display.
Picture of the scanner table
https://app.box.com/s/wfqvub4c4zcxt7etmu5fv39wgkoh6gxf
A clip of the wideband and the scanner
https://app.box.com/s/yj3jn8ieiowgvo8kfoyhat1mif7idswr
Last edited by AntiPeaceMilitias; Mar 11, 2015 at 05:44 PM. Reason: added media
Question regarding the AFRM. I've used that tuning school formula and got the same number you guys have for the NTK AFRM, the display on the afrm was showing 15.0 afr the scanner would show something like 17-18 afr.... So I played with the scanner settings and ended up using (0.363 + 7.7) and the scanner showed me the same reading as the AFRM display. Is that the correct way to do it?
Note that i did check the grounding first before manipulating the numbers to read the same as the AFRM display.
Picture of the scanner table
https://app.box.com/s/wfqvub4c4zcxt7etmu5fv39wgkoh6gxf
A clip of the wideband and the scanner
https://app.box.com/s/yj3jn8ieiowgvo8kfoyhat1mif7idswr
Note that i did check the grounding first before manipulating the numbers to read the same as the AFRM display.
Picture of the scanner table
https://app.box.com/s/wfqvub4c4zcxt7etmu5fv39wgkoh6gxf
A clip of the wideband and the scanner
https://app.box.com/s/yj3jn8ieiowgvo8kfoyhat1mif7idswr
Teching In
Joined: May 2012
Posts: 38
Likes: 0
From: Kingdom Of Bahrain
Just use what HPT has as stock for the NGK wideband. The formula I posted was for AFR conversion to E10 stoich if you tune in stoich and want to use 14.14 for E10 stoich in the VCM editor. Otherwise, leave it alone and don't try to match up the displayed AFR with what HPT reads. The output on the display is set to its own goofy formula for converting voltage into AFR.
Now it's within 0.03 between the scanner and the display. Yeah I noticed the discussion about different fuels you guys were talking about and it really helps to read all the above. I'm just using 95 gasoline here nothing fancy though.
Edit: Incase someone needs the NTK AFRM formula (volts 0.6363 + 7.67).. That worked for me