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California98Civic · 02-06-2012, 05:03 PM

Ladogaboy and I have been discussing how to read the UG's fuel trim data, and I think it might deserve a thread of its own.

The UG offers longterm and short term fuel trim readings in percentages over or under 0.00%. Whether that can translate into "lambda" and if so how to do it is the question. Here is how I am thinking of it right now, with Ladogaboy's general, qualified agreement... what do you think? Quoting the Ultra Gauge's manual on the meaning of its fuel trim readouts: "positive values indicate a lean condition exists and the injector is left open longer to compensate, thus adding more fuel" (p.17). Now that means that a UG reading of +1.56% long term fuel trim is 1.0156 lambda, a lean condition, and my car will add more fuel to maintain stoich? That's not good for fuel economy. Better would be negative percentages, indicating rich condition, in response to which the car's ECU will seek stoich by reducing fuel.

Is that correct?

02-06-2012, 05:03 PM	#1 (permalink)
California98Civic Cyborg ECU Join Date: Mar 2011 Location: Coastal Southern California Posts: 6,299 Black and Green - '98 Honda Civic DX Coupe Team Honda 90 day: 66.42 mpg (US) Black and Red - '00 Nashbar Custom built eBike 90 day: 3671.43 mpg (US) Thanks: 2,373 Thanked 2,172 Times in 1,469 Posts	How to read Ultra Gauge fuel trim data? Ladogaboy and I have been discussing how to read the UG's fuel trim data, and I think it might deserve a thread of its own. The UG offers longterm and short term fuel trim readings in percentages over or under 0.00%. Whether that can translate into "lambda" and if so how to do it is the question. Here is how I am thinking of it right now, with Ladogaboy's general, qualified agreement... what do you think? Quoting the Ultra Gauge's manual on the meaning of its fuel trim readouts: "positive values indicate a lean condition exists and the injector is left open longer to compensate, thus adding more fuel" (p.17). Now that means that a UG reading of +1.56% long term fuel trim is 1.0156 lambda, a lean condition, and my car will add more fuel to maintain stoich? That's not good for fuel economy. Better would be negative percentages, indicating rich condition, in response to which the car's ECU will seek stoich by reducing fuel. Is that correct? __________________ See my car's mod & maintenance thread and my electric bicycle's thread for ongoing projects. I will rebuild Black and Green over decades as parts die, until it becomes a different car of roughly the same shape and color. My minimum fuel economy goal is 55 mpg while averaging posted speed limits. I generally top 60 mpg. See also my Honda manual transmission specs thread.