If pressure is being measured directly at the line between the regulator, how could there be inadequate flow to the needle and seat? If there wasn't adequate volume in that line to keep a steady state of fuel at the needle and seat wouldn't the pressure reading go down? As long as the regulator can feed the volume of fuel held in that line with the needle open the pressure will remain constant. Pascals law states; "When pressure on any portion of a confined liquid is changed, the pressure on every other part of the liquid is also changed by the same amount." The needle and seat causes the volume of liquid to no longer be confined. If the needle is open the confined area must be constantly refilled equaling the exiting volume to maintain the same pressure. Obviously flow over time and quality of pure liquid could change and maybe the instruments used to monitor it aren't quick or accurate enough to record the true story. The argument about aerated fuel and using the least pressure necessary makes sense. When we use pressure vs volume maybe it isn't that we don't have adequate flow but the "quality" of the fuel being delivered isn't 100% liquid? Or am I missing something?
Doug

When you set a regulator at 5psi flowing, it has 5 psi flowing, because that is what you are telling it to flow. Has NOTHING to do with the volume, the reg is just maintaining the pressure you set it to. I test this stuff everyday on my flow bench. As an example, on the fuel side of my nitrous flow bench, the fuel reg has a .016 bleed jet to bypass fuel and keep the regulator from stacking. So lets say I set that reg to 5psi if that is my test pressure I am measuring fuel flow at. Now, I may be testing a plate system with ONE small fuel jet, or a fogger with EIGHT pretty decent size fuel jets, or just the pump running through the bleed jet. The differences in the VOLUME of fuel I pass, as measured in lb/hr can be quite large......BUT the outlet side of the regulator stays at a steady 5 psi, because that's where I set it. I do this everyday and monitor fuel flow with Rotometers, as well as pressure tranducers on a Racepak, as well as checking pressures about everywhere you can imagine, meaning before and after every piece of the system. I also have a mechanical 8 gal pump that I spin with an electric motor. I can flow a little fuel, or enough for a blown alky setup

So a too small pump can continue to supply pressure at the needle and seat, because it is regulated, but that in no way means it has adequate volume. You want to keep the bowls full, not just enough in there to run on. Which goes back to that aeration thing.

So unless I am missing what you are asking........just look at YOUR car. You know the fuel volume is much greater with the motor at full song. So does your pressure read the same with the car idling, as it does going down the track? It should.

I have proven this to guys by having them clean kill the power and neutral the car at the stripe, with the car under full power. Tow it back to the pits and pull the bowls. Have seen them basically DRY and never be a hiccup in the pressure trace on the logger graph. Not enough volume, but plenty of pressure

When you set a regulator at 5psi flowing, it has 5 psi flowing, because that is what you are telling it to flow. Has NOTHING to do with the volume, the reg is just maintaining the pressure you set it to. I test this stuff everyday on my flow bench. As an example, on the fuel side of my nitrous flow bench, the fuel reg has a .016 bleed jet to bypass fuel and keep the regulator from stacking. So lets say I set that reg to 5psi if that is my test pressure I am measuring fuel flow at. Now, I may be testing a plate system with ONE small fuel jet, or a fogger with EIGHT pretty decent size fuel jets, or just the pump running through the bleed jet. The differences in the VOLUME of fuel I pass, as measured in lb/hr can be quite large......BUT the outlet side of the regulator stays at a steady 5 psi, because that's where I set it. I do this everyday and monitor fuel flow with Rotometers, as well as pressure tranducers on a Racepak, as well as checking pressures about everywhere you can imagine, meaning before and after every piece of the system. I also have a mechanical 8 gal pump that I spin with an electric motor. I can flow a little fuel, or enough for a blown alky setup

So a too small pump can continue to supply pressure at the needle and seat, because it is regulated, but that in no way means it has adequate volume. You want to keep the bowls full, not just enough in there to run on. Which goes back to that aeration thing.

So unless I am missing what you are asking........just look at YOUR car. You know the fuel volume is much greater with the motor at full song. So does your pressure read the same with the car idling, as it does going down the track? It should.

I have proven this to guys by having them clean kill the power and neutral the car at the stripe, with the car under full power. Tow it back to the pits and pull the bowls. Have seen them basically DRY and never be a hiccup in the pressure trace on the logger graph. Not enough volume, but plenty of pressure

Ordered a set of these Holley Ultra HP bowls. I hope the baffles combined w/ lower pressure will help reduce aeration.