The fact fuel pump assemblies do arrive in different sizes makes sense, as they have to house a couple of components and bulbs depending on the model or universal donor's need for sized applications. The Fuel Pump assembly can be round or oblong, it may mount to the bottom of a fuel tank directly or with an access cover atop — all in order for manufacturers (who use many different fuel pumps depending on engine size and design, type of fuel system used by vehicle) to minimize inventory. For instance: Compact cars usually use smaller fuel pump assemblies, they are set-up for less amount of flow (down to 40-60 PSI). These pumps are small enough to fit in a variety of tanks, saving valuable space while never cutting corners on performance.
In an enlarged vehicle, such as a truck or SUV type larger fuel pump assemblies with higher rated discharge are needed. These assemblies are typically designed for high pressure, over 60 PSI of fuel flow and feed engines with greater power demands; larger displacement DOHC motors. For instance, diesel trucks will likely require specialized pump assemblies with lift pumps or dual-stage (AKA gerotor) pumps considering that the majority of diesels operate at much higher fuel pressure levels than their gas-operated counterparts... slightly above 80 PSI in some cases. These assemblies are large-sized and can accept high fuel flow demands and pressures that characterize heavy-duty applications.
The fuel pump assembly is also specific to performance vehicles. Higher performance assemblies are often bulkier and/or include high-flow fuel pumps to reach up to 300 liters per hour (LPH) versus regular passenger cars which typically run between 80-150 LPH. These larger, high-capacity pumps are designed to work with engines that have been modified and help provide optimum fuel delivery for higher rpm or increased load conditions (read: racing or towing.) These high-flow, performance fuel pump assemblies from AEM have the capacity and flow capability to support your big horsepower engine with ease.
So getting the dimensions of fuel system components correct is vital and this also extends to ensuring that fuel pump assemblies fit their intended applications perfectly, as even slight disparities in size may impact how or where certain parts can be positioned. Make sure you pick an identical size and specs replacement of the original equipment in order to function as well. Vehicle compatibility charts or advice from a mechanic are recommended to avoid fitment issues, with many aftermarket parts sometimes being slightly different in size.
Selecting the appropriately sized Fuel Pump assembly in addition to efficient fuel delivery, on any vehicle also ensures and prolongs imbibed of a long-life operation as your avoid misfit/fuel pressure inadequacy problems. Choosing the appropriate size of a fuel pump assembly is very important to make sure you have an efficient functioning system for your standard, high-performance or heavy-duty use case.