Well to put things to rest we've taken the initiative and built our own fuel pump test rig and conducted a series of tests. If anyone has any pumps to test let me know and we'll have Chewbacca run it on the test rig.

Here are some pictures of the rig






We're basically using a variable voltage power supply to run 12V and 14V to different fuel pump configurations. The pumps feed into a fuel pressure regulator and we measure the bleed-off at that pressure. We fill a graduated & calibrated container and track how much time it takes to fill, then with a simple calculation you get flow in liters per hour (LPH).

For starters the base fuel pressure in a stock fuel system is around 42psi, then it goes from there. For every 1psi of boost you add 1psi of fuel pressure. So at 20psi you're running 62psi of fuel pressure. At 28psi boost, 70psi fuel pressure. 40psi of boost, 82psi fuel pressure, and so on.

We learned a few interesting things, especially with the EVO VIII & IX pumps. The EVO VIII pump has a pressure relief valve that opens up at around 65-68psi and the flow output drops dramatically after that, eventually going to zero flow around 75-80psi. The IX pump flows a little more than the VIII pump at lower pressures but doesn't dump the flow at higher pressures. That's the reason you can make decent power at higher boost levels with the IX pump.

We also found that if feed one pump into another (series), the flow only drops slightly through the pressure range. The first pump is feeding the second pump and the second pump doesn't have to work as hard.

The best choice was the twin Walbro 255lph HP external pumps in parallel, meaning both pumps feeding the regulator.

The twin Walbro 255lph HP in-tank pumps in parallel was interesting. If you notice the flow starts dropping off at higher pressures and actually starts to get close to the performance of just one 255lph HP external pump over 90psi. The in-tank 255lph HP Walbro pumps have a pressure relief valve that starts to dump flow at roughly 85psi and the output flow drops.

 

Looks like fun boys, good info. Tell Chewie I said thanks!

 

Great test. May post this one to the articles