Ideally, to me, the system would be more mechanical than electronic. I know you guys like the electronics, but I would like to see a system that didn't engage until 5psi boost, with a variable actuator that opened with boost... ... . the parameters are simple... . it would have a maximum goal of fuel economy, not power.
I think that's what I'm going to have. The link I posted earlier to the Ebay kit includes a Woodward vaporizer/regulator. It's a negative pressure regulator, such that flow through the vaporizer is linear with vacuum on the down stream side. With the sparge tube placed pre-turbo, the system is pretty much self regulating as you described. The best "simple" indicator of the fueling rate of the engine (combination of engine rpm, temperature, and load) is boost... which means that more vacuum is being pulled on the vaporizer. Thus, the end result, is the rate of propane being introduced to the engine should be proportional to the amount of diesel being injected.
This kit offers two adjustments. The kit uses a high quality honeywell pressure switch installed in the charge air cooler piping. This sets the boost pressure at which the propane starts being injected. There is also a conical adjustment screw on the sparge tube that allows you to set the maximum amount of propane flow. Thus, the only "electronic" part of the package, is a simple on-off switch mounted in the cab. It is recommended that the propane injection not be turned on until the engine is warmed up.
The Woodward vaporizer has engine coolant flowing through it; as such, the temperature (and corresponding volumetric flowrate) of the propane should be somewhat linear with respect to negative pressure in the intake tube.
a major contributor to that is the lack of readily available propane refilling stations, state mandated trained refilling "technicians", and the voalitility of something most people don't understand. I have no problem with it, but your DOT tanks have to be recertified to be refilled by a propane company, they have to refill them.
I suppose. Although the number of propane stations are increasing. The past few years, DOE has allotted significant subsidies for installation of new filling stations. The number of "alternative fuels" stations should only increase in coming years. Another benefit, is 88% of propane in the U. S. comes directly from the U. S. Of the remaining 12%, more than half of that comes from either Canada or Mexico. I have a very friendly propane station less than 2 miles from my house.
Water and methanol are simple, and won't kill you in your sleep as easily..... they can simply be filled from a 5 gallon can and left alone. As far as injecting methanol and water, I think you're over reaching a certain amount
I've looked at water/methanol as well. For cooling alone, it looks like a ~12% mix of methyl alcohol in water offers better latent heat of vaporization than either water or methanol alone. From what I've found, water injection and propane don't accomplish the same thing. The MPG benefit of water injection doesn't come from burning more fuel; rather, from what I understand, it offers lower pumping loss, denser intake charge, better ring sealing, and possibly some net work from expansion of the superheated water vapor. The "methanol" part of water/meth injection only comes into play as an occasional power adder. To run a percentage of methanol greater than 12% to gain benefits as a "fuel", is not cost effetive in my opinion, if your goal is efficiency. Water injection works best if it can be progressively controlled, and can be used up to 50% flowrate of diesel for best economy. However, at most, you're gaining a mile or two per gallon under optimum conditions. I suppose you could run a methanol mixture high enough to add some fuel, but it is much less forgiving than propane in significant quantities. It would take a complex control system, fancy engine tuning (which 1st gens aren't capable of), and consisntant mixtures of meth/water (which is anything but cheap). Furthermore, if you ran out of meth/water on a trip, the engine would NOT be close to optimized any more, and unless you had sensing and alternate control maps, could be harmful to the engine. With a propane fumigation system, if you run out of propane, you can simply flip the switch off, and continue driving on an optimized diesel platform.
Assuming in higher concentrations, propane begins to compression ignite enough to cause knocking/pre-ignition/high pressure rise rate, the addition of water injection (NOT water/meth) serves to increase ignition delay, and extend combustion duration... exactly what you need. There would definitely be a little work in balancing the water injection system with higher propane injection rates, but I think it'd be perfectly doable with simply the Cooling Mist in cab controller.
The problem with propane is the same as any other alternative fuel, it just doesn't perform as well. There is mostly no net gain once the extra cost of handling and storage is absorbed plus the fact it is just not as effective at generating power, lacks the BTU's for the volume.
I've read that some say that. One reason the price of propane is less than diesel, is to offset the btu/gallon energy content. If all you are doing is displacing diesel, then propane fumigation offers only a small advantage. However, if (as many believe) propane fumigation improves the quality of combustion, such that it also improves the combustion of the diesel, then the benefits increase. Additionally, some evidence points toward fumigation of propane shortening the burn duration... and optimizing the heat-release profile toward that of HCCI, such that better efficiency is gained by allowing the expansion of gas to move the piston with more "leverage" early in the power stroke. I understand there's gainsayers/naysayers on this aspect. However, things are falling into place so inexpensively for me that it's worth giving it a try.
--Eric
Attention: TDR Forum Junkies 
