View Poll Results: Has your VP44 failed? If so there are 4 criteria:
Did you have bigger than stock injectors?
11
10.58%
Did you have banjo fittings?
2
1.92%
Did you have a fuel box?
26
25.00%
Or were you stock as a rock?
65
62.50%
Voters: 104. You may not vote on this poll
NEED YOUR HELP **statistics on VP44 failure**
#16
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Originally posted by infidel
The size of the delivery tubing/fittings shouldn't make any difference in flow unless you are using far greater than stock amounts of fuel. The pressure relief in the VP should remain constant no matter what size of line. If anything a larger piping system will make the lift pump last longer since it isn't having to fight as much friction loss encountered by smaller tubing. Think of the larger tubing as a reservoir, once it's filled the flow in and out is the same as smaller tubing except that it can flow more without friction loss if the engine modifications require more fuel.
Don't think the poll will help you much anyway as most folks have a stock system and thus more occasions for failure.
The size of the delivery tubing/fittings shouldn't make any difference in flow unless you are using far greater than stock amounts of fuel. The pressure relief in the VP should remain constant no matter what size of line. If anything a larger piping system will make the lift pump last longer since it isn't having to fight as much friction loss encountered by smaller tubing. Think of the larger tubing as a reservoir, once it's filled the flow in and out is the same as smaller tubing except that it can flow more without friction loss if the engine modifications require more fuel.
Don't think the poll will help you much anyway as most folks have a stock system and thus more occasions for failure.
Also, I am gathering that you think that somehow drilled banjos go between the VP44 and the injectors?? THEY DON'T! Banjos are only on the supply side, between the LP and the VP.
The only "restriction" between the VP and the injectors are the injection lines, and Bill told you why they wouldn't change anything. Bigger diameter lines have been shown to make a little more power in some applications. There's no reason to think that larger lines or injectors would increase the wear on the VP at all.
Generally, VPs failures are in one of two categories: electronic, or mechanical. The electronic failures happen randomly-- no one seems to be able to pin it down, apart from theorizing that the extra heat of a high duty cycle (fueling box) may cause the bypass solenoid to overheat or cause another failure in the electronics.
The mechanical failures of the VP are not only much more common, but also almost all the same-- the distribution section seizes. Some feel this happens with fueling boxes due to the deflection of an improperly deburred edge inside the pump. In most cases, this seems to be true.
I'm not aware of a single VP failure that wasn't either a seizure (and galling, and all kinds of bad juju) or an electrical failure. Moreover, the size of the injection lines and even the injectors themselves has no bearing whatsoever on the portion of the pumps that seizes.
If anything, maybe larger injectors are beneficial to the pump only because it allows for a lower duty cycle at a given amount of fuel flow. But that's the only benefit I see to the pump.
justin
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HOHN....I hate too be the one too point this out...but is there anything other than mechanical or electrical failure?? Especially seeing as everythhing i have seen is mechanical or electrical....LOL.
sorry i had to be the one too point it out
sorry i had to be the one too point it out
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Also, I am gathering that you think that somehow drilled banjos go between the VP44 and the injectors?? THEY DON'T! Banjos are only on the supply side, between the LP and the VP.
You assume way too much. I'm very aware of where the banjo fittings are located. I'm just trying to collect a little informal information in a formal manner and trying to observe a problem that has been happening with our trucks from a quantifyable perspective and not a qualitative one. All too often one reads things like some people have this problem or most people have that problem; therefore, the only conclusion is X. And by doing so a gross, unspecific oversimplification has occured. In talking to one of my engineering professors and describing the VP44 problem he had a theory. I am not willing to put forth any more thoughts on that hypothesis as it was presented earlier becasue I don't want to influence anyone's decision to respond.
The only thing that I will say is just a basic reminder that pressure and cross sectional area of say a line or hose of some type are inversely proportional. Flow, in terms of volume and for most practical purposes that we would run into here, remains unchanged. Scott
#19
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64K total still running the original VP44
0 to 19K stock
19K to about 55K - Egde Comp and 275s
55K to current Edge Drag Comp and BD4s
At about 50K a modified max flow kit and a Holley Blue replaced the factory supply system
0 to 19K stock
19K to about 55K - Egde Comp and 275s
55K to current Edge Drag Comp and BD4s
At about 50K a modified max flow kit and a Holley Blue replaced the factory supply system
#20
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Originally posted by psalm69
Justin,
You assume way too much. I'm very aware of where the banjo fittings are located. I'm just trying to collect a little informal information in a formal manner and trying to observe a problem that has been happening with our trucks from a quantifyable perspective and not a qualitative one. All too often one reads things like some people have this problem or most people have that problem; therefore, the only conclusion is X. And by doing so a gross, unspecific oversimplification has occured. In talking to one of my engineering professors and describing the VP44 problem he had a theory. I am not willing to put forth any more thoughts on that hypothesis as it was presented earlier becasue I don't want to influence anyone's decision to respond.
The only thing that I will say is just a basic reminder that pressure and cross sectional area of say a line or hose of some type are inversely proportional. Flow, in terms of volume and for most practical purposes that we would run into here, remains unchanged. Scott
Justin,
You assume way too much. I'm very aware of where the banjo fittings are located. I'm just trying to collect a little informal information in a formal manner and trying to observe a problem that has been happening with our trucks from a quantifyable perspective and not a qualitative one. All too often one reads things like some people have this problem or most people have that problem; therefore, the only conclusion is X. And by doing so a gross, unspecific oversimplification has occured. In talking to one of my engineering professors and describing the VP44 problem he had a theory. I am not willing to put forth any more thoughts on that hypothesis as it was presented earlier becasue I don't want to influence anyone's decision to respond.
The only thing that I will say is just a basic reminder that pressure and cross sectional area of say a line or hose of some type are inversely proportional. Flow, in terms of volume and for most practical purposes that we would run into here, remains unchanged. Scott
It seems as if you are trying to conduct an anecdotal experiment to "prove" a secret hypothesis. That's hard to do. The bottom line is that no poll here would yield anything conclusive. So, there's little point to conducting it.
First, you'd have to have a sample size big enough-- 1500-- to be statistically significant.
Second, you aren't controlling for variables! As you yourself hinted in the lead post, there are a lot of variables. To be valid, you have to control the independent variables and thus allow only the dependent variable to be tested. I don't see how this accomplishes that.
The only thing that I will say is just a basic reminder that pressure and cross sectional area of say a line or hose of some type are inversely proportional. Flow, in terms of volume and for most practical purposes that we would run into here, remains unchanged
In addition, your model of the injection line is invalid. You are modeling it as if it were a constantly flowing conduit. It is NOT. Its "flow" pulses at 1/2 engine RPM.
The injection line is better modeled as a reservoir. To create the "flow", the injection pump forces more fuel into the line which increases the pressure differential in the line. Once it reaches the pop-off pressure of the injector, the injector will open, allow a certain amount of fuel to flow out, and relieve the pressure differential the injection pump created.
It's a VERY small quantity of fuel that the pump pushes, and also a small quantity that injector flows out (these are the same if we assume fuel is incompressible). Is it too much too assume fuel is incompressible?
If not, then the volume of the injection line matters nothing as long as the inlet and outlet are sufficient to allow the the flow we seek at a given pressure differential. As such, the injector will be the limit to output flow, NOT the injection line, at least until you get into some awfully huge, unstreetable injectors, like Bill hinted.
The truck I mentioned where larger lines showed a HP increase was in the 700hp club. Most of us aren't near that.
I know what you are trying to accomplish, and many have sought the same thing-- starting about 5 years ago. Nothing truly conclusive has been established.
I know your heart's in the right place, but this isn't the way to go about it.
justin
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Originally posted by HOHN
Moreover, you need to clarify your statement of pressure. Just saying "pressure" is a "gross oversimplification", because PRESSURE DOESN'T EXIST ALONE-- THERE ARE ONLY PRESSURE DIFFERENTIALS. So to have meaning, you MUST describe the two items you are comparing when you refer to "pressure."
It's a VERY small quantity of fuel that the pump pushes, and also a small quantity that injector flows out (these are the same if we assume fuel is incompressible). Is it too much too assume fuel is incompressible?
Moreover, you need to clarify your statement of pressure. Just saying "pressure" is a "gross oversimplification", because PRESSURE DOESN'T EXIST ALONE-- THERE ARE ONLY PRESSURE DIFFERENTIALS. So to have meaning, you MUST describe the two items you are comparing when you refer to "pressure."
It's a VERY small quantity of fuel that the pump pushes, and also a small quantity that injector flows out (these are the same if we assume fuel is incompressible). Is it too much too assume fuel is incompressible?
Too say that pressure does not exist without a differential pressure is incorrect, FLOW can only exist if there is a pressure differential. Pressure is a stand alone element. To say that Pressure consists of 2 elements would be correct. Pressure exists as velocity pressure, and static pressure. Velocity is the pressure created by a fluid do to the velocity of its flow. Static pressure is what we know as measurable pressure (using a gauge).
Too assume the Diesel Fuel is incompressible is acceptable, however it will compress. It is just such a minute amount that even science will neglect it.
#22
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Originally posted by HOHN
I know what you are trying to accomplish, and many have sought the same thing-- starting about 5 years ago. Nothing truly conclusive has been established.
I know your heart's in the right place, but this isn't the way to go about it.
justin
I know what you are trying to accomplish, and many have sought the same thing-- starting about 5 years ago. Nothing truly conclusive has been established.
I know your heart's in the right place, but this isn't the way to go about it.
justin
You seem to KNOW a lot. The only thing I can say with any degree of certainty is that if you don't like what I'm trying to accomplish here then ignore the thread. If you want to talk about it further just PM me and we'll take it offline. Scott
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Originally posted by ramtd02
HOHN,
Too say that pressure does not exist without a differential pressure is incorrect, FLOW can only exist if there is a pressure differential. Pressure is a stand alone element. To say that Pressure consists of 2 elements would be correct. Pressure exists as velocity pressure, and static pressure. Velocity is the pressure created by a fluid do to the velocity of its flow. Static pressure is what we know as measurable pressure (using a gauge).
Too assume the Diesel Fuel is incompressible is acceptable, however it will compress. It is just such a minute amount that even science will neglect it.
HOHN,
Too say that pressure does not exist without a differential pressure is incorrect, FLOW can only exist if there is a pressure differential. Pressure is a stand alone element. To say that Pressure consists of 2 elements would be correct. Pressure exists as velocity pressure, and static pressure. Velocity is the pressure created by a fluid do to the velocity of its flow. Static pressure is what we know as measurable pressure (using a gauge).
Too assume the Diesel Fuel is incompressible is acceptable, however it will compress. It is just such a minute amount that even science will neglect it.
It's just like Voltage, something you are very familiar with. Voltage as a standalone entity does NOT exist. We only concern ourselves with DIFFERENCES--i.e., the voltage difference between two points (like a battery and ground, two battery terminals, etc.) It is impossible to measure voltage with only one lead. That's because we must ALWAYS have a reference; thus we are measuring a difference.
You are correct that FLOW can only exist where there is a difference of pressure. Flow is nature's way of preserving stasis, trying to cancel out differences, as I mentioned before.
Pressure exists as velocity pressure, and static pressure. Velocity is the pressure created by a fluid do to the velocity of its flow. Static pressure is what we know as measurable pressure (using a gauge
There are all kinds of pressure that we encounter in the world. All are simply variations of P=F/A
I'm pretty sure we're basically saying the same thing-- just in different ways.
Scott, if I was presumptive in my "knowing", then I apologize. I think we're all after the same thing, ultimately: knowledge that will enhance the ownership experience with our trucks.
justin
#27
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My understanding of the term differential pressure better be right since I use it all the time. It is the pressure difference that exists between two points on the same line caused by friction and attributed to restrictive line sizes, fittings or filters and is easily measured by subtracting the readings of two gauges. The differential increases with flow.
I once figured what the friction loss would be on a stock 24 valve system, assuming half the flow would be return. It came out that friction loss was tolerable until the truck is getting under 4 mpg at 60 mph.
Made me wonder about usefulness of larger banjos, etc.
Personally I'll stick to my 12 valves and not worry about it.
I once figured what the friction loss would be on a stock 24 valve system, assuming half the flow would be return. It came out that friction loss was tolerable until the truck is getting under 4 mpg at 60 mph.
Made me wonder about usefulness of larger banjos, etc.
Personally I'll stick to my 12 valves and not worry about it.
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112K miles... my pump died. Driving down the highway one minute, stuck on the side of the highway the next. BUT, I'm pretty confident my failure was due to a weak lift pump.
Russ
Russ