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Closed loop Fueling

Most aftermarket ECUs and almost all factory modern ECUs have Closed loop fuel control. To obtain Closed loop fueling you must have an Oxygen sensor (O2 sensor) and an ECU able to read the voltage from it and adjust the fuel mixtures either + or -. O2 sensors come in many variants, common types ranging from 1 wire up to 6 wire and in either narrow or wide band. (see our wide band blog post)

Closed loop fuel control usually happens at idle and low engine speeds to achieve the optimum air fuel ratio (AFR) of 14.7. That is; 14.7 parts of oxygen to every 1 part of Unleaded petrol. Which gives a combination of the most efficient burning rate VS. optimum torque.

Mixtures of 15.0 - 1 for more fuel efficentcy can be common on more advanced systems but a loss in touque is usually a result, therefore resuming an AFR of 14.7 -1 when throttle is applied is typically required. Incorrectly sized injectors and poor injector spray pattern can impede a tuner from reaching this ratio in an aftermarket application.

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