StakeMan

[quote author=mariner link=board=4;threadid=7170;start=0#69266 date=1037722711]
Stakeman,

Sorry, but you just cannot "add" pressures together for hydraulic systems. The lower pressure pump will stop pumping at 7psi and just recirculate the fuel inside the pump. Only the higher pressure pump will pump to it's set pressure. Then it's own relief valve will open and divert the fuel to keep the pressure at the set 15 psi.

Mariner.

[/quote]

If what you say is true, then compound turbo's would produce the same boost pressure as the single turbo.

Don't believe me, then try it.

Rob Thomas

[quote author=drecu link=board=4;threadid=7170;start=0#69434 date=1037732594]<br>Well all i'm trying to ask is would'nt I have constant pressure since the ecm controls the pumps, I am not going to rewire the whole system I am just going to take the orig. lift pump wire &amp; splice into it so it will still work with the ecm as being 1 pump. why would this make ym pressures too high?<br><br>DRecu!<br>[/quote]<br><br><br>I didn't rewire the entire system either, I used the stock lift-pump wire harness and spliced into that, BUT it still increases pressure. Even with my new fuel system I used the factory LP harness, works like a champ.......<br><br>Later, Rob

StakeMan

Rob Thomas,
What did you do with your old setup?

Rob Thomas

[quote author=StakeMan link=board=4;threadid=7170;start=15#69556 date=1037747752]
Rob Thomas,
What did you do with your old setup?
[/quote]



The &quot;old&quot; crap is still in it's original location, I put the old lines in my trucks toolbox, so if I have a fuel pump problem, I can reinstall the old crap in about a half hour if need be.

Later, Rob

BTW, hows one wheel drive been treatin' 'ya? LOL

Sean S

hmmm... site's a bit touchy tonight.<br><br>Seems to me that depending on the pump, many will cut out, or recirculate at the stated PSI by using the inlet pressure as the reference.<br>Not sure how many check ball / diaphram there are in existance, but it it uses...say a spring loaded diaphram between the high and low sides, then extra PSI on the low side would keep the diaphram from opening until the high side had reached X amout *over* that pressure.<br><br>In the case of a simple electrical pressure switch.. it would turn off the pump at the rated pressure regardless of inlet presure (unless the switch were somehow balanced against the inlet for reference).<br><br>Just guessing<br><br>Sean

drecu

Well i'm gonna buy a FP gauge &amp; set it up &amp; see what happenes since I keep getting confused signals........ but if have more you would like to add I would love te read to help me make a discision!<br><br>DRecu!<br><br>PS I'm getting an Edge box in a few days so I think the extra pressures would help but I don't want too much!

shortfieldbreak

[quote author=StakeMan link=board=4;threadid=7170;start=15#69441 date=1037733397]<br>[quote author=mariner link=board=4;threadid=7170;start=0#69266 date=1037722711]<br>Stakeman,<br><br>Sorry, but you just cannot &quot;add&quot; pressures together for hydraulic systems. The lower pressure pump will stop pumping at 7psi and just recirculate the fuel inside the pump. Only the higher pressure pump will pump to it's set pressure. Then it's own relief valve will open and divert the fuel to keep the pressure at the set 15 psi.<br><br>Mariner.<br><br>[/quote]<br><br>If what you say is true, then compound turbo's would produce the same boost pressure as the single turbo.<br><br>Don't believe me, then try it.<br>[/quote]<br><br>Now you're talking apples and oranges. You have to keep in mind that gas (that turbos are working with) is compressible, and liquids are not (for all practical purposes). With compressible gases, you will see an increase in pressure.<br><br>With hydraulics, (assuming the pumps are set at a specific discharge pressure, not differential pressure) putting two pumps in parallel will increase the available flow at a given pressure, and will build pressure faster than with a single pump. Assuming that the recirc is set accurately at 15 psi on both pumps, you should still see 15 psi after the pump. If one is set higher, then that will be the pressure at the pump discharge.<br><br>Now let's assume that the pumps are set for a 15 psi differential. If that's the case, they'll just boost the intake pressure by 15 psi, in which case the discharge of the second pump in series would be 30 psi (assuming 0 psi at the intake of the first one, and disregarding pressure losses in the plumbing). If they're in parallel though, the output should still be 15 psi at the discharge side.<br><br>oh, and Rob, you weren't being very nice. By the time 82 posts rolls around, you should know to be a little nicer to family.<br><br>-SFB

StakeMan

SFB,<br>You are correct that the mediums are different but the principles still apply. :<br><br>Where was Rob not nice?

Nevada

Somebody please chime in here and help me out. There have been references made here to parallel versus series on the dual lift pump question. I am no hydraulics expert so please tell me if I get this. <br><br>A parallel installation would be two pumps installed so that both pumps draw directly from the tank resulting in a cumulative secondary side pressure equal to the lowest regulated pressure of either pump and a flow rate equal to the cumulative flow capability of both pumps (at the resultant lower regulated pressure).<br><br>A series installation would be two pumps installed so that one pump draws from the tank and feeds the intake of the second pump. Question, is the line pressure that is indicated in the pump specification differential pressure or absolute pressure? If differential the resultant pressure would be the sum of the pressure rating of both pumps, if absolute it would be the pressure rating of the second pump assuming that the second pump is regulated. The flow rate would be maximum at the stated rate of the second pump at max pressure, and minimum would be the flow rate of the second pump at the minimum pressure of the first pump. <br><br>I realize that there are a variety of environmental factors that would/could affect the specific values here, but I am just trying to get a handle on the basic concept.<br><br>I am confused.

shortfieldbreak

[quote author=Nevada link=board=4;threadid=7170;start=15#70440 date=1037858831]<br>A parallel installation would be two pumps installed so that both pumps draw directly from the tank resulting in a cumulative secondary side pressure equal to the lowest regulated pressure of either pump and a flow rate equal to the cumulative flow capability of both pumps (at the resultant lower regulated pressure).<br>[/quote]<br><br>You got it exactly right, except the pressure on the second side would equal the output pressure of the HIGHEST regulated pressure of the two. Once the lower rated pump cut out, the higher rated one would keep going until it's pressure, then cut out.<br><br>-SFB

Nevada

shortfieldbreak,<br><br>I presumed that after the lower regulated pump cut out, that it would bleed back the higher pressure created by the higher regulated pump. Is there typically a one way valve of some type in the pump?<br><br>How did I do on series install?<br><br>Thanks

StakeMan

[quote author=shortfieldbreak link=board=4;threadid=7170;start=15#70579 date=1037897342]<br>[quote author=Nevada link=board=4;threadid=7170;start=15#70440 date=1037858831]<br>A parallel installation would be two pumps installed so that both pumps draw directly from the tank resulting in a cumulative secondary side pressure equal to the lowest regulated pressure of either pump and a flow rate equal to the cumulative flow capability of both pumps (at the resultant lower regulated pressure).<br>[/quote]<br><br>You got it exactly right, except the pressure on the second side would equal the output pressure of the HIGHEST regulated pressure of the two. Once the lower rated pump cut out, the higher rated one would keep going until it's pressure, then cut out.<br><br>-SFB<br>[/quote]<br><br>Have you tried a dual, in series, lift pump system? Obviously not, becuase you would know that the pressure at the VP44 is close to the sum of both pumps pressure.<br>Ask around, lots of people are running dual pumps.

Haulin_in_Dixie

My observation was that pressure drop is not the problem, but volume loss is... thereby dropping the pressure because the volume is not enough. So two regulated pumps in parallel that are regulated to 15 pounds would create double the volume and maintain the 15 pounds at any volume use that the injector pump could demand. The stock pump seems minimal at best. A new one drops pressure at wot. Is not the purpose to supply enough fuel at 15 to operate the injection pump? More volume not more pressure is the key here.

Push Rod

You've almost got it nailed, Haulin', your just missing one piece of the puzzle: The lines running from the lift pump to the filter and filter to VP44 need to be opened up to allow your dual setup to maintain enough volume flow to maintain 15 PSI. Stock hardlines and stock banjo fittings are too restrictive to allow enough volume to maintain 15 PSI at full throttle. You may see 15 PSI at the outlet of the lift pump, but by the time it gets through the restrictions, you'll be down 7 or 8 PSI at WOT at the VP44 inlet.<br><br>Soooo, I believe that the solution to the lift pump blues is new lines, opened up to at least 3/8&quot; ID (inlets on the VP44 and fuel filter canister are ~3/8&quot; ID) along with a pump that would provide about 120 GPH at 15 PSI. Two Carters in parallel would accomplish this, but I'd rather see something like a Holley Black (14 PSI/140 gph) running the system.<br><br>Rod

drecu

[quote author=Push Rod link=board=4;threadid=7170;start=15#70900 date=1037936007]<br>You've almost got it nailed, Haulin', your just missing one piece of the puzzle: The lines running from the lift pump to the filter and filter to VP44 need to be opened up to allow your dual setup to maintain enough volume flow to maintain 15 PSI. Stock hardlines and stock banjo fittings are too restrictive to allow enough volume to maintain 15 PSI at full throttle. You may see 15 PSI at the outlet of the lift pump, but by the time it gets through the restrictions, you'll be down 7 or 8 PSI at WOT at the VP44 inlet.<br><br>Soooo, I believe that the solution to the lift pump blues is new lines, opened up to at least 3/8&quot; ID (inlets on the VP44 and fuel filter canister are ~3/8&quot; ID) along with a pump that would provide about 120 GPH at 15 PSI. Two Carters in parallel would accomplish this, but I'd rather see something like a Holley Black (14 PSI/140 gph) running the system.<br><br>Rod<br><br><br>[/quote]<br><br>So how well do you think my idea would work?<br><br>DRecu!