The 255-lph, in-the-tank pumps...
The 255-lph, in-the-tank pumps came in both high-pressure and low-pressure versions. The low-pressure 255 pump (12-902) flowed 233 lph at 40 psi.
Many of you may now be asking why not simply install the 255-lph fuel pump used on the early return-style fuel system into the late-model, non-return fuel systems and be done with it? Would if it were that easy. Unfortunately, the early and late fuel pumps differ in their construction. The early pumps are positive displacement while the later pumps are turbine. The later turbine pumps will stand up to pulse-width modulation, but apparently the early positive displacement pumps will not. According to Jim Bell of (Kenne Bell), the later pumps can be used in early applications, but the reverse is not true.
To find out what can be done to improve the flow rates of both the early- and late-model fuel pumps, we gathered together as many as we could get our hands on and headed over to Kenne Bell for flow bench testing. We flowed all of the available factory pumps at 40, 60, and 80 psi at 13 volts, then reflowed the three pressures at 17 volts using the Boost-a-Pump.
We chose the three different pressures to demonstrate the drop-in fuel flow generated by the pressure increase. The Boost-a-Pump was employed to demonstrate the improvements offered by increased voltage. The data should allow the readers to finalize a system that will work with their current combination. After running the factory in-the-tank pumps, we grabbed a number of after market in-the-tank and inline pumps and subjected them to the same procedure. The largest of the aftermarket pumps were flowed at Westech using the fuel turbines on their SuperFlow engine dyno. The turbine flow numbers supplied by the Super Flow engine dyno were verified physically by taking random measurements using a graduated container over time.
The first thing that should be evident from the flow numbers is that increasing the pressure from 40 to 60 psi and then again to 80 psi has a dramatic effect on pump flow. In the case of the 2V 4.6 GT fuel pump, the flow rate dropped from 158 lph at 40 psi to 115 lph at 60 psi and then down to just 65 lph at 80 psi. To put this into perspective, the pump would support over 500 hp at 40 psi (.5 BSFC), but only 215 hp at 80 psi. That is a pretty dramatic drop in fuel flow my friends. The ironic thing is that increased fuel pressure usually coincides with forced induction, so added fuel flow is needed with the increased pressure, not the other way around. Unfortunately, more pressure means less fuel flow from the pump, so you'd better make sure the pump is able to support the desired power level at your intended fuel pressure.
After running the in-the-tank...
After running the in-the-tank pumps, we turned our attention to the inline fuel pumps. This T-rex pump from Vortech flowed 162 lph at 40 psi.
Check out what happened when we increased the supply voltage to the same 4.6 GT pump from 13 to 17 volts. Running at 40 psi, the increased voltage upped the flow rate from 158 to 264 lph. Note also that the flow rate of the GT pump at 80 psi and 17 volts nearly equaled the flow rate at 40 psi with 13 volts. In most cases, the pump flow at 17 volts at 80 psi actually exceeded the flow with 13 volts at 40 psi.
The guys at Kenne Bell came up with some interesting data regarding the SVT Focus fuel pumps during flow and dyno testing. The SVT Focus pumps are a common upgrade offered for the '03-04 Cobras. Checking out the flow data, it is pretty easy to see why you might want to replace the dual Cobra pumps with the SVT Focus units. The SVT Focus pumps flow 143 lph (at 80 psi) compared to just 119 (at 80 psi) for the stock '03-up Cobra pumps.
According to Kenne Bell, the swap is not quite as easy as the flow figures would have you believe. Physically, the Focus pumps will bolt in place of the stock Cobra pumps, but the wiring is not a direct plug and play. This, of course, means you have to drop the fuel tank to perform the intended surgery. In addition to the tank removal and power- and ground-plug issues, there is also the matter of the increased current draw from the larger pumps. Apparently, the increased amp draw from the dual Focus pumps is too much for the maximum 30-amp (mini) fuse.
For proper operation, the mini-fuse assembly must be replaced by a dedicated 40-amp (standard size) fuse, to say nothing of the wiring from the fuse to the pumps. The increase of 48 lph hardly seems worth all the trouble compared to just increasing the supply voltage with a Boost-a-Pump (or other equally effective voltage amplifier). Running 17 volts increased the pump flow of each of the two Cobra pumps from 119 to 189 lph for a total gain of 140 lph.
Since we had the fuel flow bench at our disposal, we decided to run some testing on some of the more popular in-the-tank and inline fuel pump upgrades. Check out the flow results, as we ran the aftermarket pump upgrades at 40, 60 and 80 psi at both 13 and 17 volts just like the stock pumps. The in-the-tank pumps were run on the same flow bench used to test the stock pumps, while the inline pumps were flow tested using turbine readings from the Westech Superflow dyno.
Holley offers this inline...
Holley offers this inline pump (#12-920) that flowed 276 lph at 40 psi.
The test procedure was pretty straight forward. All we had to do was install the pumps, provide 13 volts (and 17V with the BAP), and adjust the pressure. The amount of fuel bypassed equaled the flow rate at the given pressure and voltage. The flow rate was recorded by the Superflow dyno, as well as physically verified by running the bypass into a graduated container over a given period of time (60 seconds). The two readings were within a couple of lph--certainly accurate enough for our needs. As with the stock in-the-tank pumps, fuel pressure fell off dramatically with pressure, and increased after upping the supply voltage.
Check out the flow rates of the Aeromotive 11104 and Barry Grant King Sumo pumps. How does 708 lph at 40 psi (at 17 volts with BAP) sound for the Aeromotive or 759 lph for the Barry Grant King Sumo? It should be noted that the Barry Grant pump will require a serious electrical system, as the amp draw was dramatically higher than any of the other pumps. Since the King Sumo pump is capable of supporting 2,500 hp at 40 psi (at 17 volts), figure this unnecessary for anything but an all-out racecar.
The flow data should help you decide which pump/voltage combination would be right for your application. Remember to accurately judge the operating pressure of your motor, especially if you plan on running a blower or turbo. While we have provided the fuel pump figures, it is important to recognize that the fuel-pump flow is only part of the fuel equation. We have included injector flow ratings and maximum power levels for many of the common injector sizes. The horsepower calculations are based on a .5 BSFC number at 43 psi. It is possible to increase the flow rating of the injector by increasing the fuel pressure.
The Aeromotive 11101 pump...
The Aeromotive 11101 pump flowed a whopping 383 lph at 40 psi and 13 volts. Upping the voltage to 17 volts increased the flow rate to 536 lph.
The Aeromotive 11104 inline...
The Aeromotive 11104 inline fuel pump was quite impressive at 512 lph at 40 psi and 13 volts.
The highest flowing pump of...
The highest flowing pump of the test belonged to Barry Grant. The King Sumo pump flowed 608 lph at 40 psi and 13 volts and an amazing 759 lph at 40 psi and 17 volts. Figure on a dedicated wiring harness for the King Sumo, as the amp draw was pretty significant on the bad boy.