CTD NUT

Exactly, that is why I was explicit in stating "if the restrictions remain constant". I am assuming pressure will also be measured in a constant location also.....ie, at the VP44 or filter assembly.

,Also, I could care less for the sake of this debate, where the pump is mounted or how efficiently it is operating. The argument was that the pump in the tank was flowing more fuel at a lower pressure, not how efficiently it is operating. Since the line size and length has not changed, the filter assembly is identical and the VP44 has not changed, it is reasonable to expect fuel system restrictions are constant. Clearly, the pump will run more efficiently since more work can be done by pushing the fuel than pulling it while consuming the same energy....assuming that is true, I can only conclude that the intank LP is a notably lower output (flowing) pump than the block mounted LP it was intended to replace.

So, how is this intank pump an improvement?

shortfieldbreak

This is true if everything is at the same elevation. If you're pumping a fluid uphill, after the same length of pipe it will show a lower pressure than the one on the level. In the case of our trucks, we're talking about a minimal elevation gain so this loss is negligible. Just making sure we keep talking apples and apples here.

This statement is incorrect. A centrifugal pump creates pressure. A displacement pump creates flow. If you were to close the discharge valve on a centrifugal pump, the pressure will level off and hold steady. If you shut the discharge valve on a displacement pump, the pressure at the outlet of the pump will go up immediately, and most likely catastrophically, stopping the pump or breaking the pump, valve, or piping. It wants to move the fluid regardless of the pressure.

The in tank pump wouldn't be a bad thing if it was in addition to the lift pump, which it apparently is not.

CTD NUT

I see I have not been specific enough here! I suppose I should have stated that a displacement pump produces flow, not pressure. I was not considering a centrifugal pump since that was not the type of pump in question. That said, I am familiar with centrifugal pumps and always had a problem with that analogy of producing pressure not flow.....after all, if you cut off 100% flow on the discharge side of a centrifugal pump you would have a high enough restriction to flow that you could say you have no flow and only pressure being produced. It is the idea of putting fluid in motion, or in the case of a 100% restriction, the attempt to put fluid in motion that allows pressure to exist in the first place, no? I am of the belief that the method of pumping is secondary with this analogy.

79warlock

I have to ask you this, have you ever done a comparison test of the flows? I have and everytime, the in-tank pump flows higher volume. I have never seen less pressure after retrofitting the in-tank pump either. These pumps were designed for stock trucks, not to put up with the fuel demand of heavily fueled trucks.

CTD NUT

No, I have not flow tested either pump......however, if you are testing free flow and not under system pressure you may find much different results. We have even seen worn out LP's that can't maintain an adequate system pressure still pass the volume test.....why? Because there is no load on the pump when it is free flowing for DC's bogus volume test. I don't want to argue with your flow data between the two pumps since I don't have a flow meter to measure the system under operating pressure. But that said, pressure is the resistance to flow....if the restrictions remain constant and the pressure has dropped with the change of a pump how would you explain that?

As to your findings of not noticing a pressure drop with the installation of an intank pump, your experience is clearly an exception to the rule around here and seems to contradict most others first hand experience with the installation of an intank of which I cannot explain.

ramroamer

Physics and math aside, 0 psi wot. is scary. I added a holley blue to the intank asa pusher and my truck loves me for it. These trucks have an appetite for fuel and the intank just starves it. But the physics lesson was a throw back to the days when I didnt pay attention anyway, but it makes sense, The more volume sales pitch is a crock!!!

dltriolo

there are all sorts of HVLP (High Volume Low Pressure) pumps. these two pump are total different in the way they work it is not like taking the old style transfer pump and putting by the tank and running in at a lower voltage for lower pressure if you did this then all that crap about physics would apply. i have a hvlp TURBINE compressor for my spray guns and its output is at 16 cfm (cubic foot per minute) of air and only about 40 psi where as my compressor for my nail gun puts out 6 cfm and about 120 psi and this is running a standard 3/8 hose in both the spray gun and the nailer two totally different compressors and two totally different results. its is the same with the transfer pumps two different types of pumps the hose would only matter if it was way smaller in diameter to make a big enough difference the hose size on the fuel pumps is big enough that it dose make much difference.

CTD NUT

I think you might be missing my point....

It does not matter what you call the pump be it a HVLP or whatever.....it does not matter what style or configuration the pump is....and it does not matter what the diameter of the hose is (as long as it stays constant...ie,unchanged). If the restrictions that create the pressure within the system remain constant and unchanged when the pump is replaced, then the only way to experience a pressure drop is because of a corresponding drop in flow (volume).

dltriolo

the unused fuel that is not consumed from the injection pump flows back to the tank. fuel constantly flows through it

J BODY

I love it when this topic comes up! Great posts guys!!

.....here's something to think about. Note the size of the orfice that is in the return line fitting.

dltriolo

since i don't really know what I'm talking about when it comes to this updated transfer pump system i did some research and found this site to be very helpful in understanding it.


http://www.glacierdieselpower.com/im...umpExposed.pdf

1-5-3-6-2-4

I love pump debates, CTD NUT is very accurate in everything he's said that I can see........

positive displacement and non-positive displacement pumps are all that I'm aware of.......neither of which create pressure. Only flow. I've never seen a pump create pressure, I've seen loads create pressure, and the static load of actually flowing through the circuit.

I've worked 4 years in hydraulics so far.......I love it. So much more to learn.

derceg

When mine went out, i replace the transfer pump on the block and added their replacement pump in the tank. Running 25 psi at idle now and 15ish at wot.

79warlock

That article proves that the pump is a good pump for stock trucks, also may be a pretty good pump for you modified guys if you can get rid of the internal regulator and install an adjustable external regulator. It's basically designed just like a gasser pump and those last a very long time.

IntakeRacing

i've installed a bunch of these now through warranty and just people upgrading and there hasn't been one fail since. which to some of the guys in the bush up here is a major step forward cause $1200 tow bills suck.