[E4ODnut]

If any system can consistently get within +-~3% over a wide range of driving conditions it is doing very well. Among others, things that have to be taken into consideration are fuel density, fuel pressure, system voltage and injector dead band time. All of these vary a bit, and some are not part of the equation. Mechanical positive displacement and turbine types sensors can be approach this kind of accuracy if calibrated at a specific flow rate, but the calibration has to be changed for different flow rates. Lab quality or fine process control systems can improve on those figures but it usually costs a lot of money.