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Posts Tagged: fuel trim

What is fuel trim?

Fuel trim — what is it and how to read it Why do we need fuel trim? Fuel trim is an adjustment to the air/fuel mixture to maintain a balanced air/fuel mixture as engine speed and load change. If you run an engine in a controlled environment with a constant air temperature, constant barometric pressure, constant engine RPM and a constant load, you wouldn’t need to modify the air/fuel mixture. Once set, you could leave it at that. But a car’s RPM and load are constantly changing as you speed … Read More

Fuel Trim

What is fuel trim? Modern automotive computers use fuel trim to vary the amount of fuel provided to the engine based on a FEEDBACK STRATEGY to accommodate wear and tear on the engine components and sensor degradation. In other words, the computer receives feedback information from many different sensors to inform the computer how good of a job it did in calculating how much fuel to add to the incoming air. The computer then adds or subtracts fuel during the next injection cycle and reviews the feedback data again, so … Read More


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