Size of a fuel pump is designated by calculating the engine fuel requirement concerning the horsepower, pressure, and flow. As an example, higher horsepower engines need pumps that can supply a much larger fuel flow commonly referred to as liters per hour (LPH). Pumps rated at roughly 150–200 LPH are more than adequate for most standard vehicles, but a high-performance engine may necessitate a pump that is greater than 300 LPH due to fuel requirements in heavy load or high RPM conditions. The right-sized fuel pump allows for proper fuel flow to the engine, eliminating the risk of starving the fuel system, which can affect performance and efficiency.
Another factor affecting pump sizing is the fuel pressure requirement as well. While most standard fuel systems run at either 40–60 PSI, turbocharged or supercharged engines typically need pumps that can step up the pressure to perhaps 100 PSI. This complicates design of the fuel pump as the receiver must be able to withstand these pressures without going into bypass mode, and therefore the fuel system must remain stable under the varying load conditions. A pump that is too small for a given pressure requirement will cause the pump to strain, which can cut its lifespan by as much as 20%, while a pump that is too big could lead to excess fuel delivery and less-efficient operation.
Another factor for sizing the fuel pump is voltage compatibility. Most pumps need a solid 12 volt supply, however many high performance pumps that are designed for higher flow and pressure demand increased power which may require upgraded wiring and relays to supply steady power. Even a properly sized pump may not perform adequately when powered by something other than solid electrical support, especially under high demand, with voltage drops reducing pump output by as much as 15 percent.
The type of fuel used also impacts fuel pump size. E85 and other blends of ethanol need approximately 20-30% more fuel volume than gasoline to make the same power; hence larger pumps are often required, and some pumps need to be ethanol-compatible. Since E85 requires them to be able to withstand high levels of alcohol, most pumps that work with ethanol are made of stainless steel and usually also have seals that are resistant to ethanol; That way, they don’t corrode as easily or function with the higher flow that E85 requires.
Attention to Detail — An engine has specific requirements of flow, pressure, and fuel type, a pump correctly matched ensures optimal performance, efficiency and longevity by supporting the needs of the engine in a variety of driving conditions. Proper sizing ensures you avoid potential problems with under delivery or too much fuel, both of which can have detrimental effects on reliable vehicle function.