Results of a test I just posted on n54tech. For those that are interested in this sort of thing. Test car is our 135i running 100% factory fuel system, E85, with an inline pump *after* the regulator to allow for higher than factory low fuel pressures. We're finding with the factory and modified high pressure pumps an inability to hold full pressure below 5500rpm at high torque levels when you push the system with certain combinations of high torque, a richer AFR targets, and 100% E85. I am hoping raising the lower inlet pressure is the answer. So far this is the only test I've done and the results were not entirely what I hoped for.
I completed some initial inline pump testing this morning. The factory low pressure sensor tilts at 87psi so I had to plumb in a mechanical gauge to monitor low pressure. You can see in the video normal fuel pressure is 70psi. Then when I click the aux pump on it jumps up to 140psi at idle. I then pull on to the track and do a short 2-3-4 run and you'll see low fuel pressure hover around 100psi.
This log is from that same video above and summarizes what I'm seeing with this. During steady single gear runs it seems to hold high pressure as well as if not better than the normal in tank Walbro @ 70psi. But during sudden load changes (like shifts) high pressure is still crapping out even with 100psi of low pressure behind it. Although it does quickly recover. Maybe a surge tank is needed? I'll have to mull over the data some more on this one.
Quote:
I completed some initial inline pump testing this morning. The factory low pressure sensor tilts at 87psi so I had to plumb in a mechanical gauge to monitor low pressure. You can see in the video normal fuel pressure is 70psi. Then when I click the aux pump on it jumps up to 140psi at idle. I then pull on to the track and do a short 2-3-4 run and you'll see low fuel pressure hover around 100psi.
This log is from that same video above and summarizes what I'm seeing with this. During steady single gear runs it seems to hold high pressure as well as if not better than the normal in tank Walbro @ 70psi. But during sudden load changes (like shifts) high pressure is still crapping out even with 100psi of low pressure behind it. Although it does quickly recover. Maybe a surge tank is needed? I'll have to mull over the data some more on this one.