Narrow Band AFR formula for Torque APP
11-26-2017, 09:42 AM
#1
Narrow Band AFR formula for Torque APP
So the front O2 sensor is hovering at .66v most of the time. How do I convert this to an AFR reading. I see various formulas and custom PID for other cars with wideband.... but what is the equation for narrow band afr measurement?
11-27-2017, 08:54 AM
#3
Re: Narrow Band AFR formula for Torque APP
Nope.
I am getting semi reasonable results with (A*256+B)/32768*14.7
but I dunno what B is... I only have 1 AFR sensor maybe that is for cars with 2 cats/pipes
.5v would be ideal is what you're saying? I am trying to see measured and the real OBDII afr commanded/measured returns nothing so getting it from the front "O2" sensor is the best I can get.
I am getting semi reasonable results with (A*256+B)/32768*14.7
but I dunno what B is... I only have 1 AFR sensor maybe that is for cars with 2 cats/pipes
.5v would be ideal is what you're saying? I am trying to see measured and the real OBDII afr commanded/measured returns nothing so getting it from the front "O2" sensor is the best I can get.
12-01-2017, 10:42 PM
#4
Re: Narrow Band AFR formula for Torque APP
In my Opinion at a narrow band lambda (OEM sensors) its uselless to try to calculate AFR values from Voltage values and i will explain why;
you should be seing closed loop AFR values with until 1/2 throttle (voltage always playing between 0.2 and 0.8V) and open loop values with more throttle (steady voltage from 0.7 to 0.99 depending on your mixture (lean or reach). In closed loop mode there is NO POINT to check the AFR, but ONLY in the OPEN LOOP mode (throttle more than 50-75%)
On petrol engines and 100% throttle you must see above 0.85V and not more than 0.95V. If you see less than 0.85V you are dangerously lean. There is not much of a calculating method to calculate narrow lambda voltage to AFR (thats why it is called "narrow), because the narrow band lambda is accurate from 0.4V(15:1) to 0.6V (14,5:1). In example on a narrow band lambda, if you see 0.9V you can't be sure if the AFR is 12,5:1 or 13,5:1. However its always safe to stay between 0.85 and 0.95V at ANY CASE and check the AFR using a wide band lambda for being more accurate.
of course this does not mean that if you change an engine parameter (such as fuel boost) you won't see the effect on the narrow band lambda also.
you should be seing closed loop AFR values with until 1/2 throttle (voltage always playing between 0.2 and 0.8V) and open loop values with more throttle (steady voltage from 0.7 to 0.99 depending on your mixture (lean or reach). In closed loop mode there is NO POINT to check the AFR, but ONLY in the OPEN LOOP mode (throttle more than 50-75%)
On petrol engines and 100% throttle you must see above 0.85V and not more than 0.95V. If you see less than 0.85V you are dangerously lean. There is not much of a calculating method to calculate narrow lambda voltage to AFR (thats why it is called "narrow), because the narrow band lambda is accurate from 0.4V(15:1) to 0.6V (14,5:1). In example on a narrow band lambda, if you see 0.9V you can't be sure if the AFR is 12,5:1 or 13,5:1. However its always safe to stay between 0.85 and 0.95V at ANY CASE and check the AFR using a wide band lambda for being more accurate.
of course this does not mean that if you change an engine parameter (such as fuel boost) you won't see the effect on the narrow band lambda also.
Last edited by turbomaniac; 12-01-2017 at 10:58 PM.
12-03-2017, 08:06 AM
#5
Honda-Tech Member
iTrader: (1)
Re: Narrow Band AFR formula for Torque APP
The problem lies in thinking of the narrowband sensor in the same way as a lambda sensor in the first place. It's meant to be more binary than that, it's just a rich/lean sensor. It's function is in no way to deliver an actual lambda value, only to indicate which side of stoich that the engine is on.
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