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Discussion Starter · #1 ·
Does anyone know how to do this on our trucks. Using my shops scanner it shows air fuel ratio in percentage, not in the typical x.xx/x way. I asked a few people who are really good with the scan tool (Snap On Modis) and they said thats the way nissans ecu interprets the air fuel ratio. Anyone have an idea? I'd like to see what the truck is doing at WOT, but the numbers make no sense to me.
 

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90 to 110 is "normal"........the lower the percentage the richer the truck is running....the higher the percentage the truck is running leaner.......
ex...108% means its on the lean side
95% means its on the rich side....
dont know if that a good explanation
 

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Discussion Starter · #3 ·
Cool, thats a start. Now is there a way to translate the % over to the normal ratios, for example is 100% equal to 14.7to1. I know a 12.5:1 is about optimal , but what would that be in the %?
 

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this form of representation of air fuel ratio is called lambda. its turning the af into a % by using 14.7 as the denominator of a fraction and the current af ratio as the numberator. if your running at 14.2 to 1 then the computer looks at it as 14.2/14.7=0.966 or 96.6%. so basically what you can do to get the af ratio in the way you want is take whatever percentage it shows you and multiply that by 14.7. example if it is showing you a percentage of 85% you would multiply .85 by 14.7 and get 12.495 to 1 is your af ratio. if the percentage its showing is 102% then multiply 1.02 by 14.7 and you get 14.994 to 1. hope this is helpfull to ya

oh and your correct most naturally aspirated motors run their best at 12.5:1 to 3.1:1 or .85 - .901 (85%-90.1%)
 

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I "think" that only the 08 and up use wideband sensors and can give the lambda readings. There was a discussion on titantalk about this a while back.
 

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Discussion Starter · #6 ·
this form of representation of air fuel ratio is called lambda. its turning the af into a % by using 14.7 as the denominator of a fraction and the current af ratio as the numberator. if your running at 14.2 to 1 then the computer looks at it as 14.2/14.7=0.966 or 96.6%. so basically what you can do to get the af ratio in the way you want is take whatever percentage it shows you and multiply that by 14.7. example if it is showing you a percentage of 85% you would multiply .85 by 14.7 and get 12.495 to 1 is your af ratio. if the percentage its showing is 102% then multiply 1.02 by 14.7 and you get 14.994 to 1. hope this is helpfull to ya

oh and your correct most naturally aspirated motors run their best at 12.5:1 to 3.1:1 or .85 - .901 (85%-90.1%)
Much appreciated, but I dont think it's correct, at least for an 06. At idle the truck sits at 101-102. Under normal to hard acceleration it jumps up to about 114, then at WOT it instantly goes to 100 and stays there until you let off the throttle a bit. I'm guessing theres no realy way to tell the AFR without a dedicated sensor or a sniffer. If anyone else knows something, let me know
 

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Much appreciated, but I dont think it's correct, at least for an 06. At idle the truck sits at 101-102. Under normal to hard acceleration it jumps up to about 114, then at WOT it instantly goes to 100 and stays there until you let off the throttle a bit. I'm guessing theres no realy way to tell the AFR without a dedicated sensor or a sniffer. If anyone else knows something, let me know
they probably use a different number for their base like say 12.5 or whatever the motor is most efficient at then lean and rich would be relative to its optimum ratio which would make sense if only 08 and up have wide band. if you can find a nice spot to get a voltage reading here is the voltage conversion that the titans use i'm sure its most likely the same for us


if you idle at 101-102 you could get a voltage reading and compensate the 1 or 2% and you have your base then you can go back to doing it the way i said before only you'll be using your new base to multiply your percentage readings by
 

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after staring at the graph there is a box that closes off the area between 10:1 and 14.7:1 which may be the only range that our non wide band o2 sensors can read which puts 100% (middle ground between 10 and 14.7) as 12.35:1. which is within the stated optimum for NA motors. if thats correct your idle is 12.47:1-12.597:1 your heavy acceleration would be 14.079:1 and your WOT 12.35:1
 

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my bullydog reads real time A/F R's
have you ever used this feature, if so does it read as a percentage or an actual ratio? if ratio what ratios have you seen
 

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thanks for posting your thread cause that shows me that what i hypothesized using that graph is most likely correct since your idle seemed to sit at 12.6 that matches redalerts idle with the conversion of using 12.35:1 as 100%. he said his idle was 101-102% well 102% converts to 12.597 or 12.6. i guess i still can't say that my conversion is 100% correct but after this i'd say its a pretty safe bet that that is what it is.
 

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I know my 08 has wide band O2 sensors---A/F WB-B1 (V) & A/F WB-B2 (V) according to my Cipher datalogs. The voltage readings appear to go from 0-5.065 volts. I'm not sure how to convert it either though. I need to research that.
 

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Discussion Starter · #14 ·
Well since it's still up in the air, I'm going to do some data logging tomorrow while I'm at work using the 02 sensor voltage graph that was posted up. I was told by two members at titan talk this is how you have to do it unless you have an AFR guage or using cipher. I'm planning on monitoring RPM, B1 and B2 sensor voltage, timing. Anything else I should be looking at or will that pretty much cover it? I also want to do another log with the 2 degree advance taken off to see if the timing will hit the same max, or if the truck pulls anything off on the top end.
 

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Well since it's still up in the air, I'm going to do some data logging tomorrow while I'm at work using the 02 sensor voltage graph that was posted up. I was told by two members at titan talk this is how you have to do it unless you have an AFR guage or using cipher. I'm planning on monitoring RPM, B1 and B2 sensor voltage, timing. Anything else I should be looking at or will that pretty much cover it? I also want to do another log with the 2 degree advance taken off to see if the timing will hit the same max, or if the truck pulls anything off on the top end.
Whats the reasoning of all this research?
 

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