Dual Stock lift pumps?
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From: Drive till ya hit a Polar Bear, then go back 50 miles
Re:Dual Stock lift pumps?
Doc,<br><br>Many are running pusher assemblies in series, and seem to be having pretty good luck with them. I don't care for them myself, as you've got another pump in the equation to worry about and a typical pusher finds itself mounted on the frame rail where its exposed to snow, rain, and salt. If someone built an in-tank pump, I'd be all over it :-)<br><br>Rod
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Re:Dual Stock lift pumps?
Can I get in on this? I used to have the pusher pump setup on my truck and got rid of it due to excessive fuel pressure 24 psi. Let me provide a quote from Carters Universal Electric Fuel Pump Installation Instructions. This pump instruction booklet is from the after market equivalent of the factory pump 15 psi at 100 gph actually it’s 97 gph but they round it up. “When Using two 2 Universal Electric Fuel Pumps they should be placed in parallel to give increased volume without excessive pressure”. Trust me placing two pumps in series does increase the pressure just like series turbos.
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From: Nanaimo, Canada
Re:Dual Stock lift pumps?
I do not believe that the ECM knows what the fuel pressure is there is no sensor in the fuel circuit (that I know of). The fuel pressure created in the fuel system is due to the restriction in the injection pump and return lines on the cylinder head. The stock pump is a Carter vane style pump and I don't think that it is pressure regualted. If you put two pumps in sieries you will increase the pressure. If you put two pumps in parellel you will increasse the flow and possibly a increase in pressure. <br><br>Another thought on a dual pump set up is to buy the Factory Dodge pump that mounts in the tank (a gasser pump). The new fuel injection systems (gas again) seem to run at fairly high pressures with out too much troubles.<br><br>
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Re:Dual Stock lift pumps?
Mac1 <br>When I wired the pusher pump system all together I had to tap a fuse for the relay that had no voltage at key start position but had voltage in the run position. If both pumps ran while starting the engine it would case a no start flag to be placed on the ECM due to excessive fuel pressure. I drive a 2001 and the ECM does keep an eye on the fuel pressure or at least has a maximum level it sets a flag at.<br>
Top's Younger Twin
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From: Thanks Don M!
Re:Dual Stock lift pumps?
This may not be the cure all and end all to the fuel issues but here goes...
What about running one pump for moderate demand and having a switch or relay that kicks the 2nd pump on when pressures drop below say 10 psi, therefore increasing and/or maintaining volume to assist in supplying a constant supply of fuel at suffcient pressure? So when the fuel in the lines is low, the 2nd pump takes up the slack.
Just a guess.
What about running one pump for moderate demand and having a switch or relay that kicks the 2nd pump on when pressures drop below say 10 psi, therefore increasing and/or maintaining volume to assist in supplying a constant supply of fuel at suffcient pressure? So when the fuel in the lines is low, the 2nd pump takes up the slack.
Just a guess.
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Re:Dual Stock lift pumps?
OK.... I may be a newbie on THIS diesel board, but believe me, I have LOTS of experience where added "pusher" pumps are concerned - my own install is pictured at the end of this post...
1. Pumps in series DO add their individual pressures - a 5 psi pump added to a 15 psi pump WILL deliver 20 psi to the load!
2. IF the added pusher pump fails, LITTLE or NO fuel will flow with MOST commonly used pumps, since most are vane or impeller type pumps that once stopped BLOCK fuel flow, leaving you engine without fuel!
3. Our Cummins lift pumps run continuously, other than right at initial start, where they are reduced in voltage, and then only run long enough to prime the fuel system for starting - THEN, they run constantly - and any fuel pressure above their design pressure of about 16 psi is bled off by an internal ball and spring check valve, and excess fuel is routed internally from output side back to it's input - the pump is NOT turned off and on electronically by any of the engine computer systems, regardless of pressure!
4. If some think an in-tank pump is better, think again! THEY fail just like ours do - and if you think swapping out a pump that's pretty much out in the open and easy to get at is a pain, just think how much "fun" it would be to drop a partially full tank of fuel out along side some isolated road in the middle of the night would be!
5. It's been tested and PROVED that our fuel systems and the VP44 will only flow a MAXIMUM of well UNDER 50 gph TOTAL, of which the ENGINE only consumes a max of 30 gph, the rest is bypassed around the VP44 for cooling, or returned past the injectors themselves and returned to the fuel tank - regardless of mods and power adders - and while there's LOTS of debate on this particular issue, fact is, FEW of us will ever outpace the ability of out stock pumps and lines to provide the necessary flow - fancy banjo bolts and braided lines are pretty, but won't likely provide any real help in you fuel supply! For comparison, our trucks use 3/8 lines - just like the plumbing to most household faucets - go turn one of your faucets on wide open, and see how much flow you get, various restrictions and all - sure, the system pressure is higher - but get the point?
There's LOTS more info on this issue - added pushers are proving VERY effective in eliminating or at least GREATLY reducing VP44 failures - and as far as I am concerned, an absolute MUST if you're seriously interested in safeguarding your injector pump. On mine, I've added an outboard bypass around the added pusher to prevent fuel starvation in case the pusher fails for any reason - it contains in internal home-made valve that allows a large flow rate TOWARDS the engine, and a much restricted one back to the input - that was to allow fuel to continue to be sucked around the added pump if needed, and to slightly reduce total system pressure in normal operation.
I get 22 psi at idle
20 psi at cruise
18 psi at WOT
That compares to the stock pump alone:
16 psi at idle
14 at cruise
10 or so WOT
There ya have it!
Check pics below...
1. Pumps in series DO add their individual pressures - a 5 psi pump added to a 15 psi pump WILL deliver 20 psi to the load!
2. IF the added pusher pump fails, LITTLE or NO fuel will flow with MOST commonly used pumps, since most are vane or impeller type pumps that once stopped BLOCK fuel flow, leaving you engine without fuel!
3. Our Cummins lift pumps run continuously, other than right at initial start, where they are reduced in voltage, and then only run long enough to prime the fuel system for starting - THEN, they run constantly - and any fuel pressure above their design pressure of about 16 psi is bled off by an internal ball and spring check valve, and excess fuel is routed internally from output side back to it's input - the pump is NOT turned off and on electronically by any of the engine computer systems, regardless of pressure!
4. If some think an in-tank pump is better, think again! THEY fail just like ours do - and if you think swapping out a pump that's pretty much out in the open and easy to get at is a pain, just think how much "fun" it would be to drop a partially full tank of fuel out along side some isolated road in the middle of the night would be!
5. It's been tested and PROVED that our fuel systems and the VP44 will only flow a MAXIMUM of well UNDER 50 gph TOTAL, of which the ENGINE only consumes a max of 30 gph, the rest is bypassed around the VP44 for cooling, or returned past the injectors themselves and returned to the fuel tank - regardless of mods and power adders - and while there's LOTS of debate on this particular issue, fact is, FEW of us will ever outpace the ability of out stock pumps and lines to provide the necessary flow - fancy banjo bolts and braided lines are pretty, but won't likely provide any real help in you fuel supply! For comparison, our trucks use 3/8 lines - just like the plumbing to most household faucets - go turn one of your faucets on wide open, and see how much flow you get, various restrictions and all - sure, the system pressure is higher - but get the point?
There's LOTS more info on this issue - added pushers are proving VERY effective in eliminating or at least GREATLY reducing VP44 failures - and as far as I am concerned, an absolute MUST if you're seriously interested in safeguarding your injector pump. On mine, I've added an outboard bypass around the added pusher to prevent fuel starvation in case the pusher fails for any reason - it contains in internal home-made valve that allows a large flow rate TOWARDS the engine, and a much restricted one back to the input - that was to allow fuel to continue to be sucked around the added pump if needed, and to slightly reduce total system pressure in normal operation.
I get 22 psi at idle
20 psi at cruise
18 psi at WOT
That compares to the stock pump alone:
16 psi at idle
14 at cruise
10 or so WOT
There ya have it!
Check pics below...
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From: Logan, Utah
Re:Dual Stock lift pumps?
Gary,
Great post and thanks for the photos. For those of us who are new to pusher pumps, how about some explanation of your various pieces and parts. I am most curious about what appears to be a return line and the filter? on the output side. Also, what turns on the pump and when, is there a delay, is it key on? Please keep talking.
Great post and thanks for the photos. For those of us who are new to pusher pumps, how about some explanation of your various pieces and parts. I am most curious about what appears to be a return line and the filter? on the output side. Also, what turns on the pump and when, is there a delay, is it key on? Please keep talking.
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Re:Dual Stock lift pumps?
I'll post a pic at the end of this post of my individual parts used in the pump bypass...<br><br>The filter is on the INPUT side of the pusher, and is strongly suggested by Carter to enable their warranty and to eliminate coarse trash from getting into the pump and causing damage.<br><br>I use a tap into the primary circuit of the stock pump to activate a separate relay, that when activated, sends 12 volts from an independent fused source to my added pusher - you really need to do this, because the computer and VP44 are set up in such a way that if any more than about 7 psi is seen at the input to the VP44, the engine can be VERY hard to start - that's why the stock lift pump only operates momentarily when you first hit the ignition... The relay is simple to install, is an inexpensive Radio Shack item, and only draws 70 milliamps, which is a negligible additional load on the primary LP circuit.<br><br>Pic below of parts breakdown of my LP bypass...
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From: Drive till ya hit a Polar Bear, then go back 50 miles
Re:Dual Stock lift pumps?
[quote author=Gary - KJ6Q link=board=4;threadid=7170;start=30#71520 date=1038075893]
4. If some think an in-tank pump is better, think again! THEY
5. It's been tested and PROVED that our fuel systems and the VP44 will only flow a MAXIMUM of well UNDER 50 gph TOTAL, of which the ENGINE only consumes a max of 30 gph, the rest is bypassed around the VP44 for cooling, or returned past the injectors themselves and returned to the fuel tank - regardless of mods and power adders - and while there's LOTS of debate on this particular issue, fact is, FEW of us will ever outpace the ability of out stock pumps and lines to provide the necessary flow - fancy banjo bolts and braided lines are pretty, but won't likely provide any real help in you fuel supply! For comparison, our trucks use 3/8 lines - just like the plumbing to most household faucets - go turn one of your faucets on wide open, and see how much flow you get, various restrictions and all - sure, the system pressure is higher - but get the point?
proving VERY effective in eliminating or at least GREATLY reducing VP44 failures - and as far as I am concerned, an [/quote]
Good post Gary, but I've got a couple points to add:
4) In tank pumps are _much_ more reliable than our little Carter, even if they are more difficult to swap out. Talking to a local Dodge mechanic, the in-tank pumps on gassers appear to hold out for about 100,000 miles. My own time with gasser Dodges supports this. The average Carter lift pump: 30,000 miles. Personally, I didn't get that lucky with my lift pumps on my 03. I was getting 15,000 miles out of a lift pump, and others who run our terrible Canuck diesel report similar numbers.
5) Even though we may never see more than 50 gph flow through the system (Just curious where these numbers come from. Cummins mechs up here have measured 30 gph flow from just the injector return line) the idea of larger banjo bolts and larger filter/injector supply lines is to reduce back pressure on the transfer pump. 70% (another Dodge number) of Carter lift pump failures have been traced back to relief valve malfunction, a direct result of too much back pressure on the pump. Reduce the back pressure, reduce the strain on the transfer pump, increase life expectancy.
After swapping stock and lightly modified (EZs) trucks to high flow banjos, we've typically seen a 1 - 2 PSI increase (at WOT) on the outlet of the fuel filter canister. And we've seen increased lift pump life. On my 01's 4th lift pump, I had 30K, and it still registered a full 15 PSI at idle. Other trucks who have had lift pump failures have reported similar life expectancy increases from switching to high flow banjos. I don't believe that opening up lines/banjos is the cure, but it is definitely is part of the solution.
Rod
4. If some think an in-tank pump is better, think again! THEY
5. It's been tested and PROVED that our fuel systems and the VP44 will only flow a MAXIMUM of well UNDER 50 gph TOTAL, of which the ENGINE only consumes a max of 30 gph, the rest is bypassed around the VP44 for cooling, or returned past the injectors themselves and returned to the fuel tank - regardless of mods and power adders - and while there's LOTS of debate on this particular issue, fact is, FEW of us will ever outpace the ability of out stock pumps and lines to provide the necessary flow - fancy banjo bolts and braided lines are pretty, but won't likely provide any real help in you fuel supply! For comparison, our trucks use 3/8 lines - just like the plumbing to most household faucets - go turn one of your faucets on wide open, and see how much flow you get, various restrictions and all - sure, the system pressure is higher - but get the point?
proving VERY effective in eliminating or at least GREATLY reducing VP44 failures - and as far as I am concerned, an [/quote]
Good post Gary, but I've got a couple points to add:
4) In tank pumps are _much_ more reliable than our little Carter, even if they are more difficult to swap out. Talking to a local Dodge mechanic, the in-tank pumps on gassers appear to hold out for about 100,000 miles. My own time with gasser Dodges supports this. The average Carter lift pump: 30,000 miles. Personally, I didn't get that lucky with my lift pumps on my 03. I was getting 15,000 miles out of a lift pump, and others who run our terrible Canuck diesel report similar numbers.
5) Even though we may never see more than 50 gph flow through the system (Just curious where these numbers come from. Cummins mechs up here have measured 30 gph flow from just the injector return line) the idea of larger banjo bolts and larger filter/injector supply lines is to reduce back pressure on the transfer pump. 70% (another Dodge number) of Carter lift pump failures have been traced back to relief valve malfunction, a direct result of too much back pressure on the pump. Reduce the back pressure, reduce the strain on the transfer pump, increase life expectancy.
After swapping stock and lightly modified (EZs) trucks to high flow banjos, we've typically seen a 1 - 2 PSI increase (at WOT) on the outlet of the fuel filter canister. And we've seen increased lift pump life. On my 01's 4th lift pump, I had 30K, and it still registered a full 15 PSI at idle. Other trucks who have had lift pump failures have reported similar life expectancy increases from switching to high flow banjos. I don't believe that opening up lines/banjos is the cure, but it is definitely is part of the solution.
Rod
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Re:Dual Stock lift pumps?
HOooKAaay!
Want VP44 and fuel line info? HERE it is:
VP44:
http://216.235.147.117/forums/showth...+ultimate+VP44
Fuel lines:
http://216.235.147.117/forums/showth...amp;pagenumber
Those pointers will take you to the Turbo Diesel Register - UNDOUBTEDLY the absolutely BEST source of Dodge/Cummins info...
It's been a while since I read thru both those threads, hope my fuzzy memory hasn't failed me...
I wouldn't pretend to be any expert on in-tank pumps and their universal longevity - but I *can* tell you that their failure rate was EXTREMELY high in the '98 Camaro SS's like mine - and the guys owning those were as agitated and actively looking for alternatives as WE are here! Maybe other makes are better...
As far as measured flow rates are concerned, that 30 gph rating IS the fuel being returned to the tank - NOW, calculate the MAXIMUM GPH the typical Cummins in our trucks is likely to consume, and add that to the return flow...
Up a steep grade, pulling a heavy load, WOT - 5 MPG? You're doing 50 MPH = 10 GPH consumed + 30 GPH returned to tank = 40 GPH total flow? Am I far off? ;D
AND, while I agree in principle that "larger is better" where fuel lines are considered, IF we can agree that the flow thru a line will be largely determined by the SMALLEST restriction IN that line, look at the picture of the pump opening in the pic below, and then tell me how much flow improvement you'll likely get just with fancy bolts and garden-hose size fuel lines...
Keep in mind that that threaded opening is for a 3/8 fitting - THEN look at the pump opening itself...
Want VP44 and fuel line info? HERE it is:
VP44:
http://216.235.147.117/forums/showth...+ultimate+VP44
Fuel lines:
http://216.235.147.117/forums/showth...amp;pagenumber
Those pointers will take you to the Turbo Diesel Register - UNDOUBTEDLY the absolutely BEST source of Dodge/Cummins info...
It's been a while since I read thru both those threads, hope my fuzzy memory hasn't failed me...
I wouldn't pretend to be any expert on in-tank pumps and their universal longevity - but I *can* tell you that their failure rate was EXTREMELY high in the '98 Camaro SS's like mine - and the guys owning those were as agitated and actively looking for alternatives as WE are here! Maybe other makes are better...
As far as measured flow rates are concerned, that 30 gph rating IS the fuel being returned to the tank - NOW, calculate the MAXIMUM GPH the typical Cummins in our trucks is likely to consume, and add that to the return flow...
Up a steep grade, pulling a heavy load, WOT - 5 MPG? You're doing 50 MPH = 10 GPH consumed + 30 GPH returned to tank = 40 GPH total flow? Am I far off? ;D
AND, while I agree in principle that "larger is better" where fuel lines are considered, IF we can agree that the flow thru a line will be largely determined by the SMALLEST restriction IN that line, look at the picture of the pump opening in the pic below, and then tell me how much flow improvement you'll likely get just with fancy bolts and garden-hose size fuel lines...
Keep in mind that that threaded opening is for a 3/8 fitting - THEN look at the pump opening itself...
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From: Drive till ya hit a Polar Bear, then go back 50 miles
Re:Dual Stock lift pumps?
[quote author=Gary - KJ6Q link=board=4;threadid=7170;start=30#71647 date=1038104856]<br>As far as measured flow rates are concerned, that 30 gph rating IS the fuel being returned to the tank - NOW, calculate the MAXIMUM GPH the typical Cummins in our trucks is likely to consume, and add that to the return flow...<br><br>Up a steep grade, pulling a heavy load, WOT - 5 MPG? You're doing 50 MPH = 10 GPH consumed + 30 GPH returned to tank = 40 GPH total flow? Am I far off? ;D<br><br>AND, while I agree in principle that "larger is better" where fuel lines are considered, IF we can agree that the flow thru a line will be largely determined by the SMALLEST restriction IN that line, look at the picture of the pump opening in the pic below, and then tell me how much flow improvement you'll likely get just with fancy bolts and garden-hose size fuel lines... <br><br>Keep in mind that that threaded opening is for a 3/8 fitting - THEN look at the pump opening itself...<br>[/quote]<br><br>You're not too far off the mark, however I'd go with closer to 3 MPG to bring my Canuck brothers into the loop. At 60 MPH, this rates to a flow of 20 gph. I've seen the mileage computers drop like this under heavy loads with winter diesel. Whether this is an accurate number or not, I'd still say 20 GPH is a reasonable MAX flow figure. Now the VP44 return line hasn't been taken into consideration in your calculations either. According to some numbers I've seen (variety of sources, mostly Cummins/Bosch), the VP44 return will often see 45 GPH.<br><br>So we're looking at a flow demand of:<br><br>20 GPH (cylinder injection) + 30 GPH (Return from injector return) + 45 GPH (VP44 return) = 95 GPH. Awful close to the factory lift pump rating, n'est pas? This is a practical max flow. In theory, this could be much higher, as Bosch states the VP44 would like to return up to 70% of its inlet fuel for cooling purposes.<br><br>Your picture of the fuel inlet is informative, however it is also a little misleading. While the fitting on the VP44 is 3/8", the factory hardlines are 1/8" I.D. I believe (my own memory may be fuzzy here too) that the VP inlet is 1/4". So we should be able to open up the lines to at least 1/4" ID pipe. But back pressure on the line is not simply a function of outlet size. A 3/8" I.D. line with a 1/4" I.D. outlet will have less back pressure and higher flow than a line thats 1/4" ID all the way through. Friction losses and some other fancy fluid dynamics terms that I don't understand come into play here. ;D<br><br>And we also appear to be talking apples/oranges. You're talking flow to the VP44. Indeed the factory hardlines are probably adequate for providing flow to the '44. I'm talking reduction of back pressure in the system to preserve lift pump integrity. The only way to accomplish this is to open up the lines/banjos or eliminate the fuel filter (obviously not a solution).<br><br>Rod
<br><br>Keep in mind that that threaded opening is for a 3/8 fitting - THEN look at the pump opening itself...<br>[/quote]<br><br>You're not too far off the mark, however I'd go with closer to 3 MPG to bring my Canuck brothers into the loop. At 60 MPH, this rates to a flow of 20 gph. I've seen the mileage computers drop like this under heavy loads with winter diesel. Whether this is an accurate number or not, I'd still say 20 GPH is a reasonable MAX flow figure. Now the VP44 return line hasn't been taken into consideration in your calculations either. According to some numbers I've seen (variety of sources, mostly Cummins/Bosch), the VP44 return will often see 45 GPH.<br><br>So we're looking at a flow demand of:<br><br>20 GPH (cylinder injection) + 30 GPH (Return from injector return) + 45 GPH (VP44 return) = 95 GPH. Awful close to the factory lift pump rating, n'est pas? This is a practical max flow. In theory, this could be much higher, as Bosch states the VP44 would like to return up to 70% of its inlet fuel for cooling purposes.<br><br>Your picture of the fuel inlet is informative, however it is also a little misleading. While the fitting on the VP44 is 3/8", the factory hardlines are 1/8" I.D. I believe (my own memory may be fuzzy here too) that the VP inlet is 1/4". So we should be able to open up the lines to at least 1/4" ID pipe. But back pressure on the line is not simply a function of outlet size. A 3/8" I.D. line with a 1/4" I.D. outlet will have less back pressure and higher flow than a line thats 1/4" ID all the way through. Friction losses and some other fancy fluid dynamics terms that I don't understand come into play here. ;D<br><br>And we also appear to be talking apples/oranges. You're talking flow to the VP44. Indeed the factory hardlines are probably adequate for providing flow to the '44. I'm talking reduction of back pressure in the system to preserve lift pump integrity. The only way to accomplish this is to open up the lines/banjos or eliminate the fuel filter (obviously not a solution).<br><br>Rod
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Re:Dual Stock lift pumps?
"Now the VP44 return line hasn't been taken into consideration in your calculations either."
Old age and Alzheimers may have taken their toll - and I'd have to completely re-read the whole thread pointed to above - but I'm pretty sure the 30 GPH figure WAS the TOTAL fuel returned to the tank - both injector bypass AND VP44 bypass - by actual measurement, not an offhand from-the-hip guess by a Cummins tech - AND, THAT was figures done on a Cummins putting out in the 500 RW HP range - not a stocker!
Proof? How about THIS:
"well some of you guys ain't gonna like this , especially those led to believe (and those that believe it) ... the bigger is a MUST theory .
spent a couple minutes running some tests with a DIGITAL/mechnical flow meter and a MECHNICAL fuel pressure gauge , items under test ... 2000 RAM , DD2's , DD TTPM on level 2 (??) and a HOT PE , ( all levels tested the same at WOT)factory pickup , factory lift pump , factory fuel filter housing unmodified , all banjo bolts intact and unmodified except the banjo to the input of the lift pump is replaced with a 90* swept areoquip type -6AN hose end , the bolt at the lift pump had the schrader cut off and drilled and tapped to a 1/8 npt ( for the gauge) and the banjo fittings between the lift pump and the fitler housing have been drilled to 9/32nd . again all banjo bolts are not drilled out as i have on my ram ( test conducted on the DTT RAM ) .
we installed ( LaserBob is helping me and getting #2 fuel poured on his head ) a Sonnex digital flow meter ( inside ID is 5/16" in the return line back to the tank , cut in right at the trans crossmember . gph numbers are fuel returned to the tank .
DD2 , DD TTPM
FP volume
idle 11 psi 18gph
cruise 8 psi 24gph
WOT 2 psi 30gph
DD2 , TTPM , HOT PE ANY LEVEL
FP volume
idle 11 psi 18gph
cruise 8psi 24gph
WOT 0 psi 30gph
yes you read that correctly , fuel pressure went to 0 and the fuel volume back to the tank did not change from WOT with 2 psi . the truck did NOT stumble , buck , spit , fart , fall on it's face , nothing , ran like all heck at 0 psi , i will note , my truck ran the same at 0 psi with the DD3's , EZ and a HOT PE .
tomorrow we will install -8 lines and an HP carter pump , take flow readings in exact same spot and see what the results are ."
SOOOoo - what happened with larger lines etc?
THIS:
"well , here we go again , todays test was interesting to say the least , and we believe we have it figured out .
added the carter HP 15psi 110gph pump on the frame rail next to the tank , -8 bulkhead in the bottom center of the tank , -8 line to the pump , -6 line from this pump to the inlet of an unmodified factory 2000 fuel filter housing , the rest of the system is as delievered from the factory except for a banjo bolt that had the schrader cut off and tapped to 1/8 npt for the gauge , the digital flow meter in the exact same location reading flow back to tank after the tee on the engine .
with DD2 , DDTM
psi volume
idle 11.5psi 18gph
cruise 9psi 24gph
WOT 6 psi 30gph
with the HOT PE on any level
idle 11.5psi 18gph
cruise 9psi 24gph
WOT 4psi 30gph
with the addition of the new pump and larger gravity fed pickup point the flow to the tank did not change , though pressure was up , the carter having an internal bypass is living with the backpressure on its output .
the concenus is the VP44 is the restriction . the return line from the pump is only returning the excess fuel from the VP44's own internal pump , the more you feed it the higher the backpressure on the line to the pump .
the guys with the large pumps , bigger lines and regulator mounted as close to the VP44 as possible have a large amount of the excess flow returned directly to the tank , this is not a bad thing ,( except that at a low fuel level it is possible to foam the fuel in the tank with the large amount of fuel dumping back into it from 2 sources ) but is really overkill as the vp44 uses a set amount of fuel and this is proved by the higher pressure seen with no increase in flow back to the tank ."
Notice that no matter WHAT they did, the TOTAL fuel returned to the tank remained 30GPH! And NO WAY are MOST of our trucks gonna consume an additional 20 GPH in anywhere NEAR normal usage regardless of aftermarket add-ons...
Later in the thread, it's pointed out that flow back to the tank IS measuring both VP44 fuel bypass AND the return fuel from the injectors COMBINED... Also in that thread, the point IS made that the MAXIMUM flow rate thru the VP44 is 45 GPH - that includes fuel bypassed AND fuel actually consumed - and THAT is probably where the 45 GPH figure came from you were quoted - but that is a MAXIMUM, *total* flow figure, not simply what is bypassed...
Bottom line here is, no matter HOW big a fuel line you run to the VP44, it can only flow 45 GPH *max* - larger lines for the benefit of various pump schemes *might* be a good thing - sure aren't gonna HURT anything - but don't expect miracles from their use, or expect that bigger lines alone will seriously impact VP44 lifespan...
Hey - I've got pages and pages of this stuff - can provide as many as needed! ;D ;D
Read the threads - those aren't just shadetree mechanics - there are guys posting there who are aftermarket manufacturers of performance parts and guys operating their own independent diesel performance shops - they make their livings doing this stuff...
Old age and Alzheimers may have taken their toll - and I'd have to completely re-read the whole thread pointed to above - but I'm pretty sure the 30 GPH figure WAS the TOTAL fuel returned to the tank - both injector bypass AND VP44 bypass - by actual measurement, not an offhand from-the-hip guess by a Cummins tech - AND, THAT was figures done on a Cummins putting out in the 500 RW HP range - not a stocker!
Proof? How about THIS:
"well some of you guys ain't gonna like this , especially those led to believe (and those that believe it) ... the bigger is a MUST theory .
spent a couple minutes running some tests with a DIGITAL/mechnical flow meter and a MECHNICAL fuel pressure gauge , items under test ... 2000 RAM , DD2's , DD TTPM on level 2 (??) and a HOT PE , ( all levels tested the same at WOT)factory pickup , factory lift pump , factory fuel filter housing unmodified , all banjo bolts intact and unmodified except the banjo to the input of the lift pump is replaced with a 90* swept areoquip type -6AN hose end , the bolt at the lift pump had the schrader cut off and drilled and tapped to a 1/8 npt ( for the gauge) and the banjo fittings between the lift pump and the fitler housing have been drilled to 9/32nd . again all banjo bolts are not drilled out as i have on my ram ( test conducted on the DTT RAM ) .
we installed ( LaserBob is helping me and getting #2 fuel poured on his head ) a Sonnex digital flow meter ( inside ID is 5/16"
in the return line back to the tank , cut in right at the trans crossmember . gph numbers are fuel returned to the tank .DD2 , DD TTPM
FP volume
idle 11 psi 18gph
cruise 8 psi 24gph
WOT 2 psi 30gph
DD2 , TTPM , HOT PE ANY LEVEL
FP volume
idle 11 psi 18gph
cruise 8psi 24gph
WOT 0 psi 30gph
yes you read that correctly , fuel pressure went to 0 and the fuel volume back to the tank did not change from WOT with 2 psi . the truck did NOT stumble , buck , spit , fart , fall on it's face , nothing , ran like all heck at 0 psi , i will note , my truck ran the same at 0 psi with the DD3's , EZ and a HOT PE .
tomorrow we will install -8 lines and an HP carter pump , take flow readings in exact same spot and see what the results are ."
SOOOoo - what happened with larger lines etc?
THIS:
"well , here we go again , todays test was interesting to say the least , and we believe we have it figured out .
added the carter HP 15psi 110gph pump on the frame rail next to the tank , -8 bulkhead in the bottom center of the tank , -8 line to the pump , -6 line from this pump to the inlet of an unmodified factory 2000 fuel filter housing , the rest of the system is as delievered from the factory except for a banjo bolt that had the schrader cut off and tapped to 1/8 npt for the gauge , the digital flow meter in the exact same location reading flow back to tank after the tee on the engine .
with DD2 , DDTM
psi volume
idle 11.5psi 18gph
cruise 9psi 24gph
WOT 6 psi 30gph
with the HOT PE on any level
idle 11.5psi 18gph
cruise 9psi 24gph
WOT 4psi 30gph
with the addition of the new pump and larger gravity fed pickup point the flow to the tank did not change , though pressure was up , the carter having an internal bypass is living with the backpressure on its output .
the concenus is the VP44 is the restriction . the return line from the pump is only returning the excess fuel from the VP44's own internal pump , the more you feed it the higher the backpressure on the line to the pump .
the guys with the large pumps , bigger lines and regulator mounted as close to the VP44 as possible have a large amount of the excess flow returned directly to the tank , this is not a bad thing ,( except that at a low fuel level it is possible to foam the fuel in the tank with the large amount of fuel dumping back into it from 2 sources ) but is really overkill as the vp44 uses a set amount of fuel and this is proved by the higher pressure seen with no increase in flow back to the tank ."
Notice that no matter WHAT they did, the TOTAL fuel returned to the tank remained 30GPH! And NO WAY are MOST of our trucks gonna consume an additional 20 GPH in anywhere NEAR normal usage regardless of aftermarket add-ons...
Later in the thread, it's pointed out that flow back to the tank IS measuring both VP44 fuel bypass AND the return fuel from the injectors COMBINED... Also in that thread, the point IS made that the MAXIMUM flow rate thru the VP44 is 45 GPH - that includes fuel bypassed AND fuel actually consumed - and THAT is probably where the 45 GPH figure came from you were quoted - but that is a MAXIMUM, *total* flow figure, not simply what is bypassed...
Bottom line here is, no matter HOW big a fuel line you run to the VP44, it can only flow 45 GPH *max* - larger lines for the benefit of various pump schemes *might* be a good thing - sure aren't gonna HURT anything - but don't expect miracles from their use, or expect that bigger lines alone will seriously impact VP44 lifespan...
Hey - I've got pages and pages of this stuff - can provide as many as needed! ;D ;D
Read the threads - those aren't just shadetree mechanics - there are guys posting there who are aftermarket manufacturers of performance parts and guys operating their own independent diesel performance shops - they make their livings doing this stuff...