Interesting project.I'm trying to get my head around the 8-stroke cycle. Are you going to leave the cam alone and actually pull in a fresh charge at the start of the 'steam' power stroke? In this case you'd be throwing away the hot exhaust charge that contains most of the energy you're trying to recover, and the only thing powering your 'steam' phase would be the hot metal. In this case I'm sure that skipping half the power strokes and running water through the cylinder would cool the engine a lot, but I'm sceptical that you'll gain enough power during the steam phase to offset the friction and pumping losses. I suspect you'll end up with a very rough engine with about half the power and a dead loss cooling system.But it's interesting enough as a concept that I'd like to see how it works in practice.I suppose that to do this properly you'd need to replace the cam drive system with one that ran at 1/3 crankshaft speed instead of half crankshaft speed, and you'd need to change the cam phase/durations. Getting a custom cam grind isn't technically difficult but needs money and engineering skills. Changing the chainwheel/pulley sizes to change the cam speed is something that is easy in theory but may not be possible in practice, depending on the design of your cam drive. It seems to me that this is the only approach that is likely to work well, though.How are you implementing the water injection? Are you injecting into the cylinder? What sort of injectors and water supply system are you planning?What sort of duty cycle are you envisaging for the water injectors? The petrol injectors are probably batch fired, but your water injectors would need to be sequential and accurately phased, so they'll need to be sized to use a much shorter pulse. This may mean you can't simply drive them from the petrol injector signal. You could use the ignition LT pulse to give you a crude engine phase sensor but you still need some logic to decide which part of the engine cycle you're in and switch the fuel and water injection systems on and off.Needing sequential injection also makes it harder to choose the ECU. There are several aftermarket systems that support sequential injection up to 6 cylinders, but it rules out the experimental systems such as Megasquirt/VSMS. It would be worth doing some research though to find what state MS is up to now - last time I was involved with this they were developing a SMD controller that was planned to support lots of drivers and probably do what you need here.If you're running this setup in economy mode I guess you'll be around 3000 rpm which corresponds to 20 ms per crank revolution. If you wanted to complete the water injection within say a 45 degree period, that gives you 2.5 ms water injection duration. I wouldn't expect any difficulty achieving that with an Arduino. The pulse wouldn't need to be calibrated accurately as long as you have some scope to dial it up and down a bit to find the best compromise between water consumption and power. You'd also need outputs to disable the corresponding injector, and inputs for crank position (crank trigger wheel?), cam position (#1 spark LT?) and throttle (MAP?) so you could decide when to enable water injection and phase it correctly.
You'll need some additional way of telling whether the spark is for a particular cylinder, perhaps a flip-flop readable by the Arduino that is set by a spark to a particular cylinder and cleared by a spark to the next cylinder.
Your idea is interesting, but let me make some points. 1. Does the engine have individual valve lockout? If not, this idea (6 stroke) is impossible. 2. If you do not let the exhaust out after the combustion cycle, all ( and more) energy will be lost recompressing the now hot and expanded products of combustion. This means leaving the valve open well past TDC, or you have a severe backpressure issue. 3. Cooling the combustion chamber after the exhaust stroke, by injecting water on the next compression stroke will cause your engine to be extremely inefficient with very large heat loss to the pistons, cylinder walls, and combustion chamber in the head at the next cumbustion cycle. Additionally, the cold ( cooled ) cylinders will cause the actual combustion to be much less efficient. 4. If your goal is just to improve efficiency of the motor, re-write your advance and fuel curves and re-write them for maximum economy ( timing for peak pressures that don't detonate or just aren't too far advanced, never richer than the stoichiometric ratio for your fuel. Number 4 is worth anywhere from 5 to 30% fuel economy gain on modern emission controlled engines, current emissions calibrations rob your economy quite a bit compared to best economy calibration - and best economy calibration will generally only exceed Oxides of Nitrogen above limits occaisionally.
Hi, Have you seen this stuff:http://ecomodder.com/wiki/index.php/MPGuinohttp://www.waterduino.com/Some of the MPGDuino guys are involved with an Open Source ECU project...
1. No, the engine is a typical OHV. My idea for this is only based on a 6 stroke engine, mine would be 8 stroke, having intake and compression strokes between the exhaust and water injection strokes.2. Answered in #13. The fuel injectors on this engine are pointed at the wall of the intake manifold runners, so a lot of the fuel would be vaporized there. Do you have an estimate on how much less efficient the combustion might be due to decreased temperature in the cylinders?4. I will be doing that very soon. I added some stuff to the oil that's supposed to increase the seal between the rings and the cylinder wall and raise the compression. I also wanted to see the power increase (iPod dyno app, not perfect but better than going by feel) from any gained compression, so I don't want to tune it before I can see these results alone.
I added some stuff to the oil that's supposed to increase the seal between the rings and the cylinder wall and raise the compression.
You'll find out one way or the other soon enough, but dropping a cylinder is very obvious on mine. Having a 50% misfire I think would be quite unpleasant. But once you have your system working, it's entirely under your control whether you run the 'steam cycle' every other cycle or every third cycle or whatever.Since you're injection into the chamber at TDC you'll have a lot of pressure working against you. Have you worked out how you're generate enough water pressureIt sounds as if you have got the petrol injection cut-off sorted out but I'm still not clear how you're going to time the water injection. I get that you can trigger it from the spark, but you need to know which of the pair of cylinders is in the compression stroke. I suppose you could monitor one of the fuel injection pulses and work the engine phase out from that, if you know where the fuel injection pulse occurs in the engine cycle.I assume you would enable this whole water injection system when the load and revs corresponded to cruise conditions and leave the engine to run normally the rest of the time.Do you have any sort of cat system or EGO feedback system on this car? One thing EGO sensors don't like is having fluid dumped on them, and the missed firing cycle would throw any EGO sensing out of wack. Suppressing the fault codes is one thing, but if your ECU relies on an accurate EGO signal then it won't be happy.Given your experience working on engines, I'm sure you must be tempted to try the full 6-stroke conversion.
#4, unless this engine is very old and worn, everything you do ( and I mean everything) will not improve and may worsen your losses. There are very few lubricants that can beat oil. You can use a synthetic oil, look for independent tests to see which ones actually make an improvement by reducing friction losses in a real motor. #3, the injectors fire while the air is moving through the port, and it doesn't get on the manifold wall to any signficant degree. The reduction in efficiency... Or perhaps more appropriately, the increase in consumption between a cold cylinder and a hot one varies signficantly, but generally we're talking losses of anywhere from 10 to 40%. Google for "cold engine vs hot engine fuel consumption" or something like that, to find information on it. Injecting water before the compression stroke means that you will have to use fuel to heat the water, push the piston up against TDC and then it loses energy again as the piston drops and the water may or may recondense, but the heat is lost to the cylinder walls and combustion chamber, piston, etc. As to the idea of an 8 stroke motor... the friction and pumping losses for the 'non power' extra revolutions could not possibly be made up by anything you do. Pumping losses - that is the effort required to pull a vacuum on the closed throttle plate and to try to shove the exhaust or air out the exhaust system are the single largest factor in poor fuel economy at cruise. When you close the throttle, the amount of fuel consumed per horsepower absolutely skyrockets. Look up BSFC for throttled engines, and note how efficiency is improved when you open the throttle and produce more power. This is why tall gears at cruise work so well, because you have to open the throttle a lot, reducing pumping losses by reducing intake vacuum (raising manifold absolute pressure) while moving the car at highway speeds. As for engine controllers, look at MegaSquirt, which is a wholly programmable generic engine controller. I believe it may be open source, too, not sure. It's not cheap, but it's also not expensive.
It takes heat to turn water into steam. If you inject cold water at the top of a compression stroke, some may turn into steam, but the process of turning cold water into steam absorbs the heat from the compressed air, and the pressure will DROP, not rise. It will consume mechanical power to do this. As the piston starts down, the cooled air cools even more as the pressure drops, which can cause water to condense, further reducing the pressure against the piston going down. It will take far more power to push the piston up, inject the water, than will be recovered on the way down. There is nothing to gain here. NOTHING. It will consume water, fuel, and time, and you'll have a severe loss in fuel economy. You could, in theory, inject superheated water under high pressure, but that consumes large amoutns of fuel to heat the water and keep it compressed (not flash to steam). There is no efficiency to be gained here. None.
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