how does fuel temperature effect performance/economy? - page 3 - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.
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#30 by RabbitJockey on 26 Jul, 2012 11:36
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15psi would be over a little twice the air that an na engine would be getting. But I agree the only difference heated fuel may make would be in how it flows in the pump and injectors which probably effects timing and such and perhaps would help it mix a bit better when it first enters the swirl chamber since it will be slightly thinner from being hotter so I would image the molecules are a bit more excited. But to gain some huge mpg or power increase I am doubtful. It's always possible tho. It's just that diesels don't work like fuel injected or carbed gassers the adiabetic ideas don't really apply when the fuel is Injected at the time of combustion
the fuel being injected CREATES combustion...
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#31 by R.O.R-2.0 on 27 Jul, 2012 01:05
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Aside from the actual engineering caluclations regarding the energy required to heat the quantity of fuel to combustion temperatures, and the fact that you could realistically probably only heat the diesel to 200 degrees which is still a long way from it's flash point, there is the question of whether it's even beneficial to do this...
From my understanding, in a diesel engine, fine droplets of liquid fuel are injected into the cylinder combustion area. These droplets first vaporize (because you can't ignite a liquid) and then ignite under the heat and pressure. In doing so, the droplets travel towards the piston due to expanding gasses as they ignite, and create a flame path with a specific geometry which pushes the piston down in some specific way, part of the function of the prechamber is to direct the combustion accordingly. I think if you were to heat the diesel up to near it's flash point before injecting it, you would have problems because the diesel would basically be igniting too soon, and the combustion would have the wrong "geometry."
6.2/6.5 engines already have weak heads and gaskets, dont make it so that there is more peak cylinder pressure, that will make it LESS reliable..
you need something direct injected if you wanna play around with injecting fuel already heated to its flash point..
IDI will not easily lend its self to anything you want to do with it. IDI already burns VERY clean and efficient.. -
#32 by NintendoKD on 08 Sep, 2012 05:07
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Agreed, which is why I believe that there is indeed merit to the IDI tech yet.
found an interesting article on something along these lines, to keep the mystery out of it I will briefly explain my idea afterwards.
http://www.dieselbombers.com/general-diesel-related/2404-fuel-coolers.html
The idea is to use a heat exchanger just before the injection in the form of a tube with coolant or oil in it, may even do both. The injector lines will run right through this and pick up heat just prior to injection, not enough to flash the fuel but enough to aid in atomization and help efficiency some, in the 180~ range at maximum. Now hot fuel will inevitably return to the tank right? so I will cleverly protect the fuel lines from as much heat pre injection pump, and run the lines to a cooler built into the airbox with air flowing right over it to keep it nice and cool no loss in flow is expected, simply based on the fact that the engine is forced induction and will flow enough air at any engine speed to keep the cooler "cool". The 70~ degree fuel will then go to the injection pump, which will also be cleverly shielded from as much heat as possible "have some unique ideas. the higher viscosity will lead to higher initial pressure and lubriccation of the pump will aid in extended life, since the fuel pump acts as a one way valve, the fuel cannot simply expand and go the other way as it is pressurized and forced down it's path so fueling will need to be adjusted for this, which is fine, running slightly lean initially "and I mean slightly" will help the engine warm up and the process will start. I just need some dual spring injectors like the AAZ ones and I'll be in buisness. The concept is simple enough, I got the idea pondering about why engine heat up when they run lean?, why EGR's rise what does it take to do that? all questions led me to the same conclusion, apparently no one has really loooked at heating or cooling the fuel and what the optimum fuel temperature should be. I started this thread to explore an aspect of my plan to build a better IDI. the heads are in final production phase, I will likely have to tell tran to hold off for a few more months because I am in a transitional phase and will be at my end of active service as of this month and need to find an alternat form of employment to continue my research. If I stay in, "BIG IF" I plan to take leave and travel to the plant and survey all that my meager funds have afforded my efforts. I read the comment that folks on here believe I am bat S**T crazy, well believe what you like, they called Tesla crazy until here recently for some of the things he said and talked about. I am not holding a sign that says Jesus Freak, or the end is near, or end world hunger, or perpetual motion, I have an idea, and a dream and am pursuing it to the fullest extent possible by my very meager assets. You are all very likely much more intelligent than I, and I applaud you, let this retard explore, and learn for myself. I may not have much more time to do so. In terms of the 6.5 reliability, it is similar in fashion to the vw IDI needs head studs to hold the heads on right, see:
http://heathdiesel.com/welcome-to-our-new-site/
smart guy, running "mostly" stock at 45psi twin turbo setup. Bill is a little hard headed though "aren't we all" he probably got ridiculed a lot too poor fellah. The engines are not bullet proofed except bottom end studs, has no stock oil squirters like the vw's do, I think that with the right combination of effort, this can certainly be a viable engine technology again, not just for the 6.5 but for all IDI's. A good friend of mine builds Stanley Steamers, up in Maine. Good friend of mine, I used to think that he was bat crap crazy till I swallowed my pride and listened up. There used to be this young snot nosed kid that would hang around learning tool turning from him, by the name of Jay Leno. I soon learned more than I ever wanted to know about all things steam car related. It was soon afterwards that I had an epiphany, without going into too much detail basically it meant doubling the efficiency of the diesel engine without sacrificing power. I have been chasing that dragon ever since. I told ol Ben and he encouraged me to pursue it, said there was merit in anything that had any passion behind it. I have since asked him many a question, and some he had answers for and many more he didn't. That said, I don't plan to leave the forum community, but a little less ridicule and a little more support would be professionaly appreciated.
Semper Fidelis,
Sgt Kevin A. Davies, USMC -
#33 by 745 turbogreasel on 08 Sep, 2012 16:38
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The injector lines will run right through this and pick up heat just prior to injection, not enough to flash the fuel but enough to aid in atomization and help efficiency some, in the 180~ range at maximum
Heat transfer from the head to the injectors does that for you already. There is a reason for the heat shield between the injector and combustion chamber.
Adding heat to the air charge is a bad thing, return through a finned tranny cooler pipe wold be more to the point.
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#34 by NintendoKD on 09 Sep, 2012 02:44
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Ok, to clarify a bit more. I want to keep heat in the exhaust manifold, use heat wrap. Keep heat out/in of the intake manifold "I have my reasons" also with heat wrap. Keep heat in/out of injector and fuel lines also with heat wrap. keep heat from leaking out of coolant hoses, and "radiant" heat from building inside the bay. Basically the ICE is a heat pump, operated by principle of an air pump. I want to "control" this heat as much as possible, the diesel takes advantage of the heat side much better using thermal energy to aid in combustion. The heat shield removal will only really do so much and amount of saturation will vary on multiple values, however a physical heat exchanger will work much better at cooling the coolant, and heating the fuel. I was thinking of using oil because coolant oil coolers are common on vw's and are interchangeable, pretty easy, cheap to come by. The matter of pressure threshold and whether or not I can make this kind of exchanger work with the type of setup I have in mind is yet to be seen. I will run a line into the heat exchanger with pressure fittings on the in, and out tubes it will likely be a simple tube running parallel to the engine where all lines traverse through and exchange heat, no pressure is lost, in fact as the viscosity changes, pressure will increase to a degree which will have an effect on timing depending on fuel temperature. Thick "er", viscous fuel will enter the IP relatively cool, and exit slightly warmer, then get heated again before injection. Heat control is very important, if not then many variables will have to change, necessitating the re-design of the engine or it's individual components. This is relatively easy to do in comparison with some methods I have devised. So....... pipe for inlet outlet of coolant, drilled with four holes, injector line long enough to go through and fittings for re-connecting it on either side then weld them to prevent leaks. the other side to this is cooler intake air box air will be used to cool the fuel via heat exchanger which leads to the IP. pretty simple setup, the coolant will come post thermostat, for heat regulation, as long as the heat has reached a certain point the system will work beautifully, a solenoid can be used to mechanically regulate timing prior to a given temperature.
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#35 by NintendoKD on 09 Sep, 2012 02:46
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The injector lines will run right through this and pick up heat just prior to injection, not enough to flash the fuel but enough to aid in atomization and help efficiency some, in the 180~ range at maximum
Heat transfer from the head to the injectors does that for you already. There is a reason for the heat shield between the injector and combustion chamber.
Adding heat to the air charge is a bad thing, return through a finned tranny cooler pipe wold be more to the point.
you would indeed be correct in an N/A setup, but with a turbo the hotter charge cannot expand outward as the turbo acts as a one-way valve. -
#36 by 745 turbogreasel on 09 Sep, 2012 16:24
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If you are exchanging downstream of the turbo, under load, you will have a fuel heater, not a cooler.
NA or not, I say adding heat is bad because heat in = increased EGT = less engine life & power potential, and we have plenty of more productive ways to raise EGTs. -
#37 by NintendoKD on 09 Sep, 2012 20:29
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he he, plenty of other ways to raise egt's
we will see. I have some work to do to get that far yet.