HOHN

As usual, Bill is right on the money.

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

ramtd02

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

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

Ryan

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

HOHN

I am sure you are familiar with the scientific method, namely that you start with a hypothesis, then you conduct experiments to see if the hypothesis is valid.

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.It's worth clarifying your last point. Pressure and cross sectional area are only inversely proportional IF FLOW IS CONSTANT. 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." This is the kind of confusion that surfaces when people talk about fuel pressure and how higher fuel pressure means more flow, while some say lower fuel pressure means more flow-- they're BOTH correct, but they are measuring different things when they say "fuel pressure."

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

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.

psalm69

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

psalm69

Hey guys I only need about 15 more responses, so if you have had a failure please submit your results.

HOHN

I'd like for you to explain how I am wrong. EVERY pressure measurement is relative to something. Atmospheric pressure is relative to a vacuum-- thus, we are measuring the difference between one pressure (atmospheric) and another (a vacuum). You don't just measure pressure. When you have 30psi of boost, do you just have "30psi"? NO! You have "30psi MORE than atmospheric pressure"-- thus the difference between PSIA and PSIG. If pressure wasn't ALWAYS relative, there would be no need to distinguish between the two.

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.

Even velocity pressure is a differential, and it is in fact measurable, just like static pressure. Velocity Pressure is usually measured as inches of a water column. As an aside, have you ever explored the relationship between the appearance of pressure from velocity, and the disappearance of pressure from velocity (Bernoulli's theorem?). Guess where the pressure came from?

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

teamropin983

I had Bigger Bajo Bolts, 90 Horse Injectors and a Fuel Box When Mine Failed Hit wrong button when voted and put stock as a rock

psalm69

Justin,
No offense taken at all. I'm just a guy doing a poll.

infidel

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.

20014x4

75000 miles and two injector pumps. 1 LP. sig shows mods.

dieselminded

I went to cummins on this matter this is what they said "powermaster@cummins"-----https://www.dieseltruckresource.com/forums/showthread.php?s=&threadid=44525

CTD99

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