Fuel pumps are also tuned for pressure—meaning they will pump just the amount of fuel needed for the engine to perform correctly. For calibration, the pump needs to calibrated based on the required pressure usually measured in terms of pounds (PSI) per square inch. Stock fuel pumps for non-performance applications operate anywhere from 40–60 PSI and high performance applications can exceed over 100 PSI in order to supply turbocharged or supercharged engines. Keeping a well-balanced air-fuel ratio, which is needed for efficient combustion and engine health in general, always relies on proper calibration.
Most fuel pumps would get calibrated on a test bench, assuming that the manufacturer methods are very calibrated under controlled conditions in the test bench settings. Throughout this process, the pump is hooked up to pressure gauges that measure the output versus different simulated load conditions. It can be several cycles before the testing is complete; each cycle simulates different RPMs and different fuel demands. Pumps, like the Walbro units found in many applications, are often tuned to maintain constant fuel delivery above 300 liters per hour at pressure for higher rush engines operating at high RPM.
The internal parts — pressurizing system, a relief valve, etc. — are important to pressure calibration. These valves stop lubricants from excess buildup of pressure, protecting the pump and fuel lines from damage. Calibrated pressure relief valves release excess pressure above the calibrated threshold ensuring consistent fuel delivery, even during rapid acceleration. Expertise in valve calibration has a direct impact on pump performance, with research showing that at high loads, pumps with precisely calibrated valves break down 20% less often than pumps with poorly calibrated valves.
Calibration accuracy is influenced by voltage stability as well. Since fuel pumps depend on a reliable 12-volt supply to perform correctly, voltage fluctuations can result in varying fuel pressure. And that is where they again adjust the pump parameters during calibration to guarantee the voltage input during the entire cycle so that the variations in the vehicle electrics systems will not influence the pump operation. Over a 5% voltage drop can equal a 15% reduction in a pumps fuel delivery, and once a pump is properly calibrated this value is a direct correlation to maintaining pressure.
In calibration, it is important to control temperature—not just because heat influences the pressure stability. At the high-temperature end—typically around 85-100 degrees F—the pumps are thermally stressed in these conditions to change the calibration so that if they were to experience thermal stress, this would not let pressure drops occur. Bosch, for example, includes high-temperature simulations in its calibration process so the pumps still perform efficiently at extremes — a 10-degree rise can affect the constancy of fuel pressure.
A properly calibrated Fuel Pump provides a consistent supply of fuel for performance at different driving conditions without the risk of pressure failures during use. Pressure calibration is the critical element in tailoring the pump to the needs of the engine, enabling more precise fueling and more durability in the vehicle.