MotorSports Digest

Fuel Pump Chart

One of the great benifits of modern fuel injection is the way its closed loop fuel supply system works. With a closed loop system, the fuel is pumped from the fuel tank up to the fuel rails (where the fuel injectors are mounted) and then through a fuel pressure regulator and, finally, what isn't used is sent back to the fuel tank. With this type of system, you can run an oversized fuel pump without the fear of fuel related problems. This allows you to buy a fuel pump large enough to grow into, as well as one large enough to offer an aditional safety margin.

The following chart shows the maximum horsepower potential of the most common sized EFI fuel pumps. This isn't to say that these figures are an example of what you should try to get out of each pump size. These are only examples of the maximum that they are capable of. For all practical purposes, if you are getting near the maximum horsepower your pump can handle, now is definitely the time to step up a size or two.

Absolute Maximum Horsepower

	12 volts	14 volts	17.5 volts
88 lph 110 lph 155 lph 190 lph 255 lph 320 lph	222 hp 278 hp 391 hp 480 hp 644 hp 808 hp	267 hp 333 hp 470 hp 576 hp 773 hp 970 hp	324 hp 405 hp 571 hp 700 hp 939 hp 1178 hp

As the previous chart has shown, voltage can greatly affect the flow figures of a pump. To get a better idea of this effect, the following chart shows the effective pump size as related to voltage. One thing to keep in mind is that, as you raise the voltage to a pump, you also reduce its life span. This is why it's best to get the proper size pump as opposed to trying to get squeeze a little extra out of a pump that's just not the right size.

Effective Fuel Pump Size

	12 volts	14 volts	17.5 volts
88 lph 110 lph 155 lph 190 lph 255 lph 320 lph	73 lph 92 lph 129 lph 158 lph 213 lph 267 lph	88 lph 110 lph 155 lph 190 lph 255 lph 320 lph	107 lph 134 lph 188 lph 231 lph 310 lph 389 lph

One last thing to consider is that as you raise fuel pressure you also decrease fuel volume. While every pump responds differently to changes such as voltage, fuel pressure can have a dramatic effect on each pump. For this reason, it is very important to buy a pump that will supply the volume of fuel needed at the pressure required for your application. Understand that many OEM pumps drop off dramatically as pressure increases, while other pumps, such as the Vortech T-Rex and Walbro High Pressure Pumps, do a substantially better job at pressures of 80 psi of more.

Unfortunately, even the best pumps will still drop off volume as pressure increases. For example, the very popular Walbro 255 lph intank pump (GSS-307) supplies 255 lph at 40 psi, but drops to below 200 lph by 70 psi, and will go below 160 lph by 100 psi. At the same time, Walbro also offers another 255 lph intake pump what will work much better at the higher pressures, the GSS-340.

While it would be great to have a single chart to show these affects, it's very tough to do so as each pump responds differently. The best recomendation is to check with the manufacturer or dealer to get the information on their pumps. Only this way can you be sure that you are getting a pump that will safely support the horsepower you plan to make.