Quick way to calculate actual AFR
#1
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Quick way to calculate actual AFR
Even though I have a wideband in my car, I've been trying to find a reliable formula for calculating the actual afr from just the 02 volts. I googled the topic and found a bunch of formulas out there that do not seem to work at all. So, I started messing around with some numbers in excel. Here is the formula I came up with:
AFR = 17-(02Volts*7)
This formula is very simple, yet seems to be extremely accurate. I checked the numbers from this formula against the readings from my wideband, and they seem to be very close.
Sorry if this formula is old news or if there are better ones out there. I couldn't find anything better so please let me know if there is a more accurate formula to accomplish this.
AFR = 17-(02Volts*7)
This formula is very simple, yet seems to be extremely accurate. I checked the numbers from this formula against the readings from my wideband, and they seem to be very close.
Sorry if this formula is old news or if there are better ones out there. I couldn't find anything better so please let me know if there is a more accurate formula to accomplish this.
Last edited by djd24; Sep 25, 2006 at 08:39 PM.
#2
If you know how a narrowband O2 sensor works, then you'd know it's impossible to calculate true A/F from narrowband O2 voltage. It does not have a linear output like a wideband does. O2 voltage will vary from vehicle to vehicle, even at the same A/F. If it was that easy, widebands would be obsolete.
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Of course I do not rely on this method...I just noticed that it seemmed extremely close to my wideband readings. That would be pretty nice if there were a way to calculate AFR from 02 volts.
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#8
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Say you have a Target A/F of 12 to 1. Your A/F is 11.3. Simply take 11.3 divided by 12 which is .941. Multiply your current fuel table by .94%. This should get you close.
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#10
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Unfortunately Narrowband readings are only good for "Ballpark" values.. Nowhere near accurate enough to tune 100% safely.. I have to admit I have done it in the past.. Unfortunately EGT temps affect the accuracy of the sensor which is why they are strongly discouraged from being used.
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Originally Posted by djd24
Even though I have a wideband in my car, I've been trying to find a reliable formula for calculating the actual afr from just the 02 volts. I googled the topic and found a bunch of formulas out there that do not seem to work at all. So, I started messing around with some numbers in excel. Here is the formula I came up with:
AFR = 17-(02Volts*7)
This formula is very simple, yet seems to be extremely accurate. I checked the numbers from this formula against the readings from my wideband, and they seem to be very close.
Sorry if this formula is old news or if there are better ones out there. I couldn't find anything better so please let me know if there is a more accurate formula to accomplish this.
AFR = 17-(02Volts*7)
This formula is very simple, yet seems to be extremely accurate. I checked the numbers from this formula against the readings from my wideband, and they seem to be very close.
Sorry if this formula is old news or if there are better ones out there. I couldn't find anything better so please let me know if there is a more accurate formula to accomplish this.