Yes, one of the problems with the VP is it sends harmful pulses back to the LP. So by installing a longer RUBBER hose somewhere between the two makes for a damper. There is thought that the stock short rubber peice between the VP and the filter was intended for that very reason. That is reason enough not to mount the fuel pressure guage at the VP, but closer to the LP.
Actually it would be nice if good ol' ROD from the, no longer, Wildcat Diesel, would chime in here. He seemed to have good knowledge of the VP/LP issues. Matter of fact he was the one who found out that by enlarging the stock fuel lines, alone, you add pressure and reliabilty. And I dont know why everyone is bad on the stock LP. This is a GREAT pump! Just for a second here, think about what Cummins and DC have asked it to do. Supply a constant 15 psi through tiny restrictive 1/8" fuel lines, while sucking from a tank lower than the pump itself some 10 feet or so away, is strapped to a massive vibrating HOT engine, and getting its bypass check ball's brains beat in by the pulsations of the VP just a couple of feet away. Then the amazing part is, if you factor in the equation that there is THOUSANDS of LP's out there that have never been replaced with thousands of miles on them. Just a thought.

 

Cool deal Dieseldude, but you are pulling my leg a bit.....

There are no 2,400 MWe (electrical) 'units' in the world. Plenty of 2,400 MWe or higher 'plants' though, with several units each.

So you either meant 2,400 MWt (thermal) each unit or 2,400 MWe plant total for two units 1,200 MWe each).

And also, station service load for a 2,400 MWe pressurized water reactor plant is typically about 120 MW, not 600 MW.

You were probably referring to MWt (thermal) for each of your units. In which case you would indeed need close to 600 MWt heat input before synchronizing.

So do you work at Surry or North Anne ???

Great looking truck... It would be totally cool to have a picture of your truck, complete with nice black smoke coming out the stacks and doing a burnout right right next to the reactor containment building



Inifdel, that sounds quite interesting. but what you need to do now, is upgrade to a higher pressure boiler, and add a steam turbine generator. Then you can make electricity, and bleed off the steam at a later turbine stage for your plant oil extract work.... In this way, the steam for your research is all but free and you make money selling power.....



As for the comments on the fuel pressure, there have been tons of good remarks. The rubber hose for the pulsations, would work for sure, as long as the hose is not too stiff. Restrictive fuel lines from the tank sounds like a genuine problem. And I did not at all know about this leaky quick disconnect at the top of the tank. That sounds like a real problem.

I'm thinking, redo the fuel lines from the tank including the quick disconnect, and a nice Holley blue and all should be well.




GREAT conversing guys

Kevin




Kevin

 

Not to take away from Rods comments; but he was relaying the findings from my research and development I did.
I have feedback from folks with trucks that had stock lift pumps and the Max Flow fuel kit and well over 400 horsepower. My efforts to make the system flow easier with less restriction is what I feel netted these results. Lots of dollars and hours went into different configurations. I was finished trying when I put the last system on my 2001 a few years back. I figured if it still had failed pumps or so so pressures, I was wasting time and money and then FINALLY, the last design worked. I never let this on the market until I had 20,000 miles on the first kit.
I have continued to test and refine the fuel systems and found that the braided teflon 'could' transfer resonance. It did not always do this. The Aeroquip hose I use now is the same price as the braided teflon but is all rubber with some weave on the outer layer as well as reinforcement in the compound. This hose is REALLY resistant to chafing. Its specifically designed for Pushlock fittings.

Scotty

EDIT: Here is the link to the picture of the Weber metric adapter and the Scotty Metric adapter...its not the best picture and I will try and get a better one uploaded asap.

http://www.scottyairsystems.com/pricing.htm

Scroll down the page to see the picture.

 

i'm one of your "well over 400" customers scotty

stone stock fuel system, with the exception of the max flow kit ...

at 505 on the dyno i still see about 2 psi

thanks

 

One area not mentioned in this thread is the problems within the tank with the pickup. My system still had problems until I bottom fed the pump. I would love to se the results of an improved pickup and Scotty's hoses on the stock lift pump, probably rear mounted.

My use is commercial and reliability is the main issue, to avoid repairs while well below freezing in the parking lot somewhere on worse on the shoulder of the freeway.

The FASS was expensive, put it on, did the bottom feed. It is a flawless system. Filters last forever, fuel pressure is always between 18 and 20 at idle or wot. I have run it out of fuel once, dump some in kick the starter, a few seconds and 20 pounds. Starts right up.

I also have another guess on what Mopar was doing with fuel lines. I think there were aware of the pulsation caused by the VP so they tried a restriction coupled with a rubber piece in the line to dampen it.

I have posted this before also but feel it is critical to this subject of fuel. These engines were designed for mid sized trucks. In the mid sized use they are sold as units complete ready to run, fuel pump and all, hense the location on the engine. Go look at a mid sized truck or loader or compressor or whatever that might get one of these engine systems. Show me one that has a pickup such as Dodge puts on them. Diesel tanks have a bottom bung with the fuel line attached that goes to the fuel pump. This is what Cummins designed the system for. The Dodge system in the tank is an adaption that they built to fit the needs of the EPA regulated pickup truck. I think it is the biggest problem with the Dodge fuel system. Somehow they pickup air and at times refuse to prime.

If I had it to do all over again, the bottom feed would have been first and the lines second. But those two would be the initial fuel system mods. On the other side of things, my system I forget about. Never look at the gage. Am thinking of a warning light to come on at 6 pounds or so to warn if there is a defect in the pump.

 

HID - I very much like the idea of the bottom fuel feed.....are you talking factory tank or bed mounted tank? Also, how did you cap the stock feed?

 

Not true. The release of dissolved or entrained air (not the same thing) does NOT require a vacuum, just a simple CHANGE in pressure.

When you open a Coke, you release a lot of the gas that is stored in the can. This gas is not ONLY stored in the can as pressurized gas, but also as DISSOLVED CO2 that comes out of solution when the can is opened. At this point, the Coke is NOT under vacuum, but under atmospheric pressure.

In other words, the gas is only dissolved because it is under pressure that's greater than atmospheric.

So the release of a dissolved/entrained does NOT require that the pressure drop to a vacuum, it only has to drop far enough to change the solubility of the vapor/liquid solution.

A common case of cavitation is a boat propeller. The movement of the prop blade creates a differential in pressure which often releases vapor with a lot of force. Ever notice how painted props get the paint worn off even if they've only seen water? This is the reason.

On commercial diesels (with replaceable liners), cavitation is an issue because the liners flex in operation. The vibration of the liners transmits throught the coolant a pressure wave, which, as you may know, is simply a wave of high pressure followed immediately by a trough of much lower pressure (perhaps nearly a vacuum, even). This rapid change in pressure is what can release bubbles and cause liner pitting (known as cavitation erosion) in non-parent bore engines.

Thus, reason #1 to have an upgraded fuel system on your truck. Higher fuel pressure inside the pump SHOULD (in theory) reduce the possibility of pump cavitation. Engines running the OEM banjos AND low pressure could have major issues with this as the restrictive banjos sets up an ideal place for cavitation as the pressure drop across them is great relative to aftermarket systems.

Reason #2 for upgraded fuel system has to do with fuel flow through the pump. For a fixed orifice, flow through it is directly proportional to the pressure differential across it. Note, this is not completely linear, as you will hit a point where doubling FP will NOT double flow rate. This increased flow increases pump cooling and ensures adequate lubrication (which the stock system MAY provide already, but increasing VOLUME won't hurt).

Reason #3 has to do with HIDs comments on VP pressure pulsations. The larger the fuel line is, the more fuel is stored within it (duh). This means that the reservoir of fuel over which the vibrations are dampened is larger as well. Fluids are not superconductive of wave energy, so the more fluid the energy must travel through, the less energy remains at the end. This is exactly comparable to how a long wire has more electrical resistance than a short one does, and why extreme lengths of extension cords or discouraged.

Increasing the elasticity of the fuel lines will also serve to slighly dampen pulsations. From this perspective, a socketless style hose may be better than the braided Teflon that comes with Scotty's smart flow fuel kits. I have one of his fuel kits on my truck and love it.

I also agree with HIDs assessment of the bottom-feed superiority. I am STRONGLY considered adding a -10 or -12 bottom feed fuel bung to my tank and bypassing the OEM module entirely.

Justin

 

I bottom fed the stock tank. Take the pressure gage/ feed unit out of the tank and you have a four inch hole ot work with. A battery drill from the inside, near the center but clear of the pickup unit is good. I used an air brake frame mount bung. It sticks up about 5/16 inside but draws fine down to 32 gallons. Just plug the stock line, no big deal.

If it was not erased, I had pictures of the bung I made up in the album section. Just remember, you don't need gaskets or sealer, the tank itself is a gasket, just steel against the plastic is a good seal.

 

Hohn,

Your comments are true however in engineering terms liquids are incompressable, pressure is only attained through the hoop stress of the surrounding structures. Pulsations in liquids are not damped the same as electrical or gas pulsations as they are more dependant on the piping structure for the damping or stiffness. If the stiffness of the liquid conduit is infinite, the pulsation wave will travel for ever at the speed of sound in the liquid reflected or refacted by changes in diameter or volume area. By adding a "flexable" hose or very soft piping structure, damping is added and the waves energy is dissipated more rapidly.

On the pulsation front, there may also be a resonant frequency of the fluid in the piping between the lift pump/filter and VP44. This resonance may occur at a certain RPM/Pump speed and flow rate which over time would cause the failure to happen more quickly... This is why I would like to measure these pressure pulsations. Maybe by adding another 2-4" of hosing would put the resonance above any damaging speed or load. The pulsation dampeners or "pots" seen on liquid plunger pumps are designed for only 1 resonant frequency and do not remove all pulsations.

 

I don't know if I insinuated that liquids are compressible-- I didn't try to. Truth is, they are very slightly compressible, and the more gas is dissolved in them, the more compressible they are.

But, in engineering terms, their compressibility is so insignificant that it is completely disregarded. They are, for all practical purposes, incompressible, as you stated.

The increased damping from the increased volume of fuel contained by a larger line is present, but VERY small-- perhaps insignificant as well. I didn't mean to imply that this alone is going to save your LP-- just that it doesn't hurt any.

I've toyed with the idea of replumbing my Scotty Fuel system with socketless hose, which offers some damping more than the braided teflon does-- at least it would seem to be the case.

I, too , would like to see what these pulsations look like. It would be nice to hook up a scope and print out the graph. You could then calculate ideal fuel line length for a given RPM.

Couldn't an expansion chamber of some kind also serve to dampen pulses? Imagine like a rubber balloon with an inlet and outlet.

I'm no techie guy, but I sometime try to play one on DTR

Justin

 

You play pretty good, had me fooled at least
Chris

 

Hohn,

Thats what I was thinking... You could use certain diameter tubing and a pulsation volume to tune the fuel system. If you could get most of the pulsations under control that do the most damage, probably low frequency such as 1X or 2X the VP vane pump-vane passing speed (ya its hard to explain) then you may be free and clear to get a few more ponies out of the VP without damage. Not to mention the increased life of the pump which we all would like to see I am sure.

 

Hohn:





No it is not a simple change in pressure, its a sudden drop in pressure. I assure you, there will never be any gasses or vapors flashing out of solution with an increase in pressure. If we are talking about water vapor flashing out of our fuel than at any temperature under 212 F then we most definately are talking about a vacuum. To be exact, if our diesel fuel is roughly 80F it would take a vacuum of roughly 28.9" Hg to get the vapor to flash, so yes we are talking about a deep vaccum.




Totally and completely incorrect. Flow through an orifice follows the square law at all times. The flow is not directly proportional at all.. It is proportional to the square root of the pressure differential. Thus twice the pressure is 1.414 times the flow, four times the pressure doubles the flow etc. this is a basic law which is unarguable. If you want to play techie,first learn the rules.


What we are talking about here is essentially the NPSH at any given instant of the entrance to the sleeve within the VP44. As lildog correctly brought up, it could in fact be going negative at that point, while where we measure it entering the VP it is still positive.



Kevin

 

I'm wondering how the scope would hook up to the line? I guess I'm not understanding what instrument can be used to turn the pulsations into voltage that the scope can read?

I know my fuel pressure guage that's plumbed 3 feet from the VP on 3/8" parker rubber fuel line will rattle and buzz like crazy unless the needle valve is almost completely shut. The fuel guage has 7ft of 1/4" stainless/teflon line after the needle valve.

brandon.

 

The pressure measurement would actually be quite simple. I use 0-2000 Psi pressure transducers for my analyser on engines and compressors in the Oil and Gas field, for compressor pressures, engine peak firing pressures etc. There are many diffrent types such as Piezio or strain gauge.

The problem is finding a transducer that has the resolution down in the "0" gauge pressure range. If you don't have the resolution you can't get good data.

The pressure sensors are about the size of a pencil in diameter and around 1-1.5" long typically and are ICP powered. In that you have to feed it a constant voltage and measure the 4-20 milliamp output signal. This translates to a time wave form that can be converted into Frequency data using Fast Furior (Sp?) Transform or FFT. There are FFT analysers or like the one I have that does FFT, Time base and Crank Angle based.

You would likely have to tee into the same spot as your gauge port, there are adapters for 1/4" NPT, and you may have to swedge down. Or you may have to fab up your own tee.

The cost of the transducer is the stumbling part, usually around $1200-1500 USD just for the AC transducers. The DC or absolute transducers are safely double.. Like I say I may have contacts in the industry that have one of these special pressure range x-ducers..