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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Air Fuel Gauge 02 Sensor Lambda Sensor
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<blockquote data-quote="Magnetoman" data-source="post: 106609" data-attributes="member: 2806"><p>If exactly the right amount of fuel and air had been mixed in the carburetor (i.e. a stoichiometric mix) and combustion was complete there would be no free oxygen left. With the canonical "gasoline" of yore an AFR of 14.7:1 was stochiometric. However, with pure ethanol it is 9:1, and for in-between mixes the AFR is in-between (e.g. 13.8:1 for 15% ethanol). This would seem to be a problem for using our wideband gauges. But, it's not.</p><p></p><p>A sensor detects the amount of free oxygen that comes out of the combustion chamber, not the AFR. of whatever goes in. If there is no free oxygen left after combustion that condition is λ=1.00 irrespective of the fuel used. If there is excess oxygen (i.e. the mixture fed to the engine was lean) λ will be greater than 1.0 and if there is unburned fuel (rich) λ will be less than 1.0. Most engines provide maximum power for λ in the range of approximately 0.82-0.88.</p><p></p><p>For the convenience of people who don't like Greek letters most/many/all of these wideband sensors will multiply λ by 14.7 and display the resulting "AFR" instead of, or along with, λ. For gasoline with fairly low ethanol content the desired range would be ~12-13:1. However, the calculated "AFR" is never anything other than an approximation.</p><p></p><p>So, to answer Robert's question, you shouldn't be looking for any AFR range at all. You should be looking for a λ range, because λ measures the actual product of the combustion irrespective of the composition of the fuel.</p></blockquote><p></p>
[QUOTE="Magnetoman, post: 106609, member: 2806"] If exactly the right amount of fuel and air had been mixed in the carburetor (i.e. a stoichiometric mix) and combustion was complete there would be no free oxygen left. With the canonical "gasoline" of yore an AFR of 14.7:1 was stochiometric. However, with pure ethanol it is 9:1, and for in-between mixes the AFR is in-between (e.g. 13.8:1 for 15% ethanol). This would seem to be a problem for using our wideband gauges. But, it's not. A sensor detects the amount of free oxygen that comes out of the combustion chamber, not the AFR. of whatever goes in. If there is no free oxygen left after combustion that condition is λ=1.00 irrespective of the fuel used. If there is excess oxygen (i.e. the mixture fed to the engine was lean) λ will be greater than 1.0 and if there is unburned fuel (rich) λ will be less than 1.0. Most engines provide maximum power for λ in the range of approximately 0.82-0.88. For the convenience of people who don't like Greek letters most/many/all of these wideband sensors will multiply λ by 14.7 and display the resulting "AFR" instead of, or along with, λ. For gasoline with fairly low ethanol content the desired range would be ~12-13:1. However, the calculated "AFR" is never anything other than an approximation. So, to answer Robert's question, you shouldn't be looking for any AFR range at all. You should be looking for a λ range, because λ measures the actual product of the combustion irrespective of the composition of the fuel. [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Air Fuel Gauge 02 Sensor Lambda Sensor
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