Good question about fuel pump requirements. There are a few things to know about this subject.
First of all, lets look at the stock Mustang's fuel pump. It is only an 88 Liter per hour pump. That's all that Ford found necessary for the 225 HP 5.0 engine. Now, most Mustang guys that modify their cars will tell you that as horsepower increases, so does the need for fuel, so stepping up to a bigger fuel pump becomes necessary. Ford offers a 110lph, a 155lph, a 190lph and a 255lph fuel pump upgrade for Mustang owners. The Ford fuel pumps all mount inside the fuel tank. Now for us Mopar guys, these pumps won't work unless we mount them inside our fuel tanks. Fortunately, the aftermarket has many fuel pumps that will work for us. The key is that the fuel pump has to be an EXTERNALLY mounted fuel pump. External pumps are designed to pull fuel from the tank and send the fuel to the engine. Internal pumps are designed for in-tank use only. These pumps send fuel from the tank to the engine and do not pull fuel the same way that an external pump is designed to do.
If you call a company like Summit Racing and ask, they can recommend several aftermarket EFI external fuel pumps that will work. (Edelbrock, Compucar, NOS, Holley, Aeromotive, etc.) But before selecting a pump, figure out what you want to do with the engine (Supercharging, naturally aspirated or NOS) and guestimate the engine's HP level. This information will help with fuel pump and fuel line size selection.
For example, a supercharged EFI engine has a different and more demanding fuel requirement than a naturally aspirated EFI engine. Naturally aspirated engines only need about 38 to 45 psi to function properly. In a supercharged application the psi requirement changes. Included with most supercharger kits is a device called an FMU (Fuel Management Unit). This unit restricts the return of fuel back to the gas tank under boost. By causing this increased restriction, the fuel pressure goes up under boost. Depending on your fuel injector size and the amount of boost your engine is running, the psi can easily go from 45 psi to 60 or 90 psi. The increased psi is what forces the additional amount of fuel into the engine under boost. The increase in fuel pressure is porportionate to the increase in boost. The proportionate increase of fuel pressure under boost is called the "step-up ratio." Why is this significant for fuel pump selection you might ask? It's significant because 60psi to 90psi is what separates some of the naturally aspirated fuel pumps from the higher capacity race oriented pumps. Some smaller fuel pumps cannot sustain higher psi levels (60 to 90psi) and deliver the correct volume of fuel at this higher pressure. In otherwords, get a good pump if you plan to supercharge or run nitrous. [ VERY IMPORTANT NOTE] In supercharged and nitrous applications, you NEVER want to run the engine lean. .....unless you want to replace your blown headgaskets or melted pistons. So, getting the right capacity fuel pump is important.
I use an externally mounted fuel pump by Aeromotive. I believe that it is an A1000 fuel pump. This pump will support approximately 700 supercharged horsepower. My fuel lines and my fuel pump are much bigger than necessary for a naturally aspirated application. I plan to supercharge my engine, so I got the big stuff right from the start.
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