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Forget the math part, the opener and closing are the important part of describing how complicated modeling the rail is. One good point is that temperture, and fuel flow speed are relative unimportant. No model they came up with worked at all engine speeds! It pretty much describes our problems, and if you look at the graphs, the harmonics or water hammer problem is worse at low speeds. The also point to the end of the rails as place that dampening happens. So now my WAG, I would say that the regulator mods are really just changing the dampening effect. What reading this article made me think that the real reason for seeing better results is that the hoses being used in all these mods are acting as dampers. I also think the check valves are Ford's attempt at damping the system. So how about feeding the rail at both ends with check valves at both ends and using hoses to feed them. That should dramatical effect the end of rail reflections. Since nos 8 is near the end of the rail that has no dampening the standing wave reflections are the greatess. They also mention that rail pressure had a fairly significant effect on harmonic pressure changes. www.fs.isy.liu.se/Publications/MSc/00_EX_3081_KA.pdf This article also to me gives rise to doubt that Kim's injectors can fix the problem of rail harmonics. They are cause by the closing of the injector and stoping the fuel flow leading to hammering. I guess Kim's injectors could be engineered to be less sensitive to the standing waves and thus achieve more consistent fuel delivery. If that what he has accomplished, then I hope he does get his patent and everybody can pay him for his injector design. |
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CKing I believe the fuel system as Ford had it was in fact a dead end fuel rail system, thus the harmonic spikes had no where to go, especially when the CV were in place. Thats the reasons for the water hammer, engine knock and noisy injectors (air from crappy fuel lines & tank design). Once the aftermarket fuel regulator was added, this gave the fuel an escape route via the return on the regulator. I think this automaticly dampened the harmonics. Additionally when the CV's are removed and the fuel is fed to both rear heads and regulated at both front ports, the fuel has an inlet AND an outlet.....a complete route, eliminating the dead in issue. I have felt the hoses by hand before and after my re-plumb. I can tell you the pulses inside the hoses are not near as harsh as before. What is accomplished by all of this....moving (pushing) a lot more fuel, giving the injectors all/what they need, giving air a way out of the system via the factory shimmed regualator. This is all good stuff. I am just wondering what will happen when winter comes and temps get low. Does the operating pressures have to change? I don't know. Edited by Rooster (05/28/02 11:47 AM) |
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CKing, I have always believed that the types of phenomenon discussed in that article could well be the root cause for several months now and nothing I've seen has changed my opinion and my novice testing to date has only added weight to the pressure shock wave/harmonic source of our cackle and idle knock problems. However, understanding and implementing a solution is not trivial in its engineering design, but IMHO probably very simplistic in actual design implementation and installation. This is why with 200 views you have only two responses to your thread - this is NOT a simple and easy problem to understand and engineer an effective solution to. Three months ago HERE I proposed an approach to an actual solution for these phenomenon and most recently indicated as what I believed should be tried HERE and HERE and still feel that something along these lines might really help. Larry |
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The article deals with dead end rails and the problems. So I still think those that have changed the system to be open at both ends ie. a return line have just change lengthed the length of the rail. Again the hoses due give some and move. From looking at the picture of the check valves they do not close the rail, the shock wave would move right past them before they could close due to the velocity of the wave in diesel fuel. If they were opening and closing they would probably hammer themselves to death. I THINK they are an attempt to catch the wave on it way back. They could also be tuned to Interact with the standing waves and act a particular frequency like a damped oscillator. I really wish Kim would talk more about his solution. Also looking forward to reports on injector wear. |
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wow after reading all that i feel like i should be staying at a holiday inn express. my brain hurts now. good paper |
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CKing, In reply to: I don't read the article that way since figure 2.1 on page 3 the actual fuel rail is fed from one end and is returned to the tank on the opposite end and even has an injector fuel return going back to the tank so what is being modeled is very similiar to the TT regulator mod on our vehicles. I don't consider this a dead end fuel rail. In reply to: Again, I just have a different view based on my understanding of what is being modeled in the article and the fuel systems on our vehicles. The fuel path in our heads from my understanding enters the head thru a CV not in the fuel rail proper but thru a fitting into a passageway in the head and travels down to the actual fuel rail where it makes a 90 deg convoluted turn thru this banjo type fitting shown in the picture in the link HERE . Until Bob Riley has fittings make up that can be used/modified in the actual fuel rails to date nothing that has been done that has actually changed the physical geometry of the fuel rails directly. There are two geometries here, one is the actual fuel rail and the other is the feed and/or return passageways in the heads themselves that intersect the actual fuel rail thru these fuel rail drain plugs shown in the link above. While connected via this fuel rail drain banjo type plug, pressure/shockwaves will be transmitted thru them the actual geometry of the fuel rails themselves and it's acoustical properties has changed little. The only thing that has actually changed is what ever acoustical property the return line passage in the head that is normally dead ended with a plug in the back of the driver's side and front of the passenger's side of the heads has been changed when it is opened up for the return in the TT regulator mods. How this change effects the normal acoutical feedback to the fuel rail itself effects the acoustics in the fuel rail proper is the only thing that has changed. If you look at the figure 2.1 on page 3 in the article you referenced the one big difference if this figure is an accurate representation of what was being modeled is that in the system in the article was actually being fed and returned in the ends of the fuel rail itself directly and not thru this convoluted path thru a 90 deg turn and redirected by these banjo type fuel rail drain plugs like on our fuel systems. Also the system being modeled in the article has injection pipes that feed each injector from the fuel rail itself whereas our injectors have no such injection pipe geometry. The modeling of these injection pipes as an input to the fuel rail is described on page 12 in section 3.2. If our stock system were to be modeled the only injection pipe input for the fuel rail would be that from the reflected/harmonic structure in the normally pluged test ports on the back of the driver's side and front of the passenger's side of our heads. I just can't envision this input having a major contribution to the fuel rail acoustic properties after it makes this 90 deg turn and flows thru these convoluted passages in this banjo type fuel rail drain plug. With that said I am still somewhat at a loss to understand exactly how what has actually changed to achieve the undisbuted success in balancing the CP on #8 with the regulated return installed by TT/Doug on his test vehicles. To date the only plausible reason that I have(ON EDIT change the have to "can") personally give any weight to is that if significant entrained air is being released by whatever process in the fuel rails themselves and either pocketing or occuring physically near an injector, then getting a flow in the fuel rail will physically move this air away from where ever it was causing a problem in a non flowing fuel rail. Larry Edited by Larry M (05/29/02 11:09 AM) |
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And the whole dam cackle issue would NOT be a problem if we had the T444e fuel system. The T444e fuel system has not only a regulator but also an accumulator. It feeds both heads from one end and the return comes out the other end. Pretty darn simple and standard diesel design. Ahh then Ford decides they can design a better fuel system, that's where the whole mess originates from. Go look at a T444e and you'll see what I mean. If I can get the T444e fuel system to fit on my truck that is what will happen. I just haven't gotten all the parts together yet, but i'm getting close! See ya, Shane |
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beantown, Don't forget the brain(PCM/ECM). From my understanding International has their own which from my understanding is a lot faster than ours, is designed for their fuel system, and is not adaptable to our automatic transmissions. Larry |
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Dang it Larry SLOW down will ya! lol  I'm just trying to get the plumbing done first. Now about that PCM/ECM. Your right that it probably won't work with our tranny. But I just so happen to have an totaled International 4700 (electrical company line truck)that just happens to be four wheel drive with a guess what auto in it! HEHE Allison in my future?? If I do that the tranny hump might grow a couple of inches! Hey if I can cram a 350 chevy under a CJ-2A jeep hood that tranny ain't no big deal! If I do put the tranny in I can't wait to take it to Ford for service and see the look on the mechanics face the first time he looks under the truck!
See ya, Shane |
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Perhaps some sort of accumulator could be in place? This is the effect of the rubber hoses, to dampen pulses, which is the primary function of an accumulator. I dont know, just my first reaction. |
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I realize that I am making stabs in the dark trying to understand what is occurring in our engines so I'll throw the following out. What would be the combined effect of pressure harmonics in the fuel rail and injector cavitation. I had posted the following study on injector cavitation earlier and I must admit that I am not even sure whether our injectors would fall into the categories of nozzle types that is discussed. http://www.ecs.umass.edu/mie/faculty/schmidt/ISTP.pdf second study: http://cav2001.library.caltech.edu/documents/disk0/00/00/02/57/00000257-00/cav2001.pdf Ken Edited by wkw (05/29/02 10:41 AM) |
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Body lift |
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Larry, Does the shock wave that is traveling through the diesel fluid care about a 90 degree turn? Since it is a wave with very little to no movement of the fluid it doesn't have inertia. If you don't have inertia from moving mass you can turn corners without problems. I remember something about this in fluid dynamics but that is a very looooong time ago. Anybody younger remember any of that stuff. Isn't that how you dampen a wave of this sort by letting move some mass? |
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Damping a wave is usually done through destructive phase interference. What that means is parts of the wave are reflected back onto itself to mess-up the "wave-like" motion. Large to small diameter changes do a good job at this. This is how the baffles in a muffler work. A variable volume container & bladder can also damp out a wave. A 90 degree turn will act like a wave splitter. Part going down the 90 and part reflecting backwards. |
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CKing, In reply to: From what I know and understand a lot of what you say is true in viewing this shockwave in the time domain, however it is not true when viewed in the frequency domain. What is being looked at here is not really a fluid dynamics type scenario. Pressures will transfer well around corners, but standing waves, harmonics are very path and geometry sensitive and as ssls6 has said the reflection and interference of these pressure waves (a time domain event) and their paths effect greatly what the frequency domain looks like. I guess one example might be to take two long narrow boxes with water in them. One is straight and the other has a 90 deg bend. Drop a stone, etc. in the straight box and see how the pressure wave travels down the box and do the same with the angled box and these peaks and valleys will not be the same. The frequency domain representation of these peaks and valleys in the fluid is what is of concern in the modeling in the article. In fact if you took a lot of pebbles/rocks and dropped them on a fixed periodic basis in the same point in each box you could very easy see three distinct and different pressure wave patterns, one in the straight box, one in one leg of the angled box, and a different one in the other leg of the angled box. This is really hard to explain in words and I only hope I haven't confused the issue more in my feeble attempt to explain my understanding of all this  - this is bordering on PhD level knowledge which I do not have - I only have enought to not only be dangerous to myself most of the time, but destructive to others in trying to explain it.
Larry |
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Not a bad explanation. The examples works well in my mind. |
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Larry, What I'm trying to picture is looking at it from inside the injector as if you were in the preshot chamber when it opens. Have we got two things happening then that effects the fill of the pre shot? The pressure wave should effect how fast the pre shot can fill. What I don't know is if the time allowed to fill the preshot is relatively long as compared to the amount of fuel needed. So it may not really be an issue. Or are the Standing Wave harmonics causing something similiar to cavitation so the preshot ends up getting a bubble? Anybody know the workings of our injectors well enough to answer the question about how much time to fill the injector? |
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CKing, In reply to: I really don't understand enough about how the actual injectors work. I take as a given based on everything that I have heard and that people like FMTRVT have shown in his fuel pressure plots that their are large pressure spikes in the fuel rails from whatever source. In reply to: I have said this all along. The fill of the injector could be disrubted from what I see as three sources. A direct pressure wave, a standing wave or a harmonic wave, or even a simple relfected pressure wave. An example of the first for instance would be #6 shock wave direct path creating a low pressure region just as #8 pre shot should happen or even #6 shock wave hitting the end of the rail where #8 is and doing the same thing on it's "bounce" off the end of the rail. A multitude of other combos are possible along with a potential release of entrained air in or around a particular injector or injectors could also be the source as a result of at least the direct or reflected pressure interacting with something. Problem here is that I have no idea which is correct and have seen nothing to say one is more likely than the other except based on my previous comments on explaining the sucess that TT/Doug has demonstrated in the flow thru the head scenario, I commented on in my post HERE. If someone held a gun to my head today and told me I had to vote, my vote at this point would be something is causing an explosive air release event around injector #8 that is messing up it's operation. If this is the problem then providing a flow might help the problem with #8 and the more I hear of problems starting to creap into strange noises coming from the passenger side after the mods are done only adds weight to this potential source. Consider if this is what is messing up the filling of #8 and the flow is moving this pocket of air enough so #8 fills O.K. what is preventing an opposite effect over in the passenger side - i.e. the air pocket has now unintentionaly been moved from a benign area to some injector over on that side of the engine that now creates the problem that the flow solved for #8 on the driver's side to some injector on the passenger side. This is something that I am currently chewing on and hope I don't choke on it  because there is a lot to ponder here and "muse" further on.
Larry |
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Larry M Most of these mods have included connecting a line from the rear of the driver side head to the front of the passenger side head. The next cylinder in the firing sequence after 6 and 8 is the front cyl on the passenger side. |
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What are the nozzels on our injector tips like. Eg. How many, what size, distribution etc. I came across many studies that concerned injector cavition and actually tracked down and corresponded with a professor at UMass that authoured one such study. What is the combination of effects of air entrained fuel that is cavitating at the injector nozzle while also under the influence of the wave/pressure harmonics of the fuel rail while also experiencing the pressure oscillations of all the injectors opening and closing. Is this our cackle? Ken |
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Great Post on Rail Harmonics, My WAG solution to Cackle
