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| Getting an electronic fuel injector to only open partially |
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| sokoloff:
--- Quote from: ELS122 on June 04, 2023, 05:13:44 am ---at 8000rpm, the whole intake cycle happens in around 2 miliseconds, --- End quote --- At 8000 RPM, each cylinder in a four-stroke engine is doing 4000 intake cycles per minute or 67 per second. You also have some valve overlap and intake air flow inertia, so you have nearly an order of magnitude longer than you’ve calculated. |
| HighVoltage:
1. You need a PWM signal to the injectors, that will give you better control over the injector timing, opening lift.... 2. Best to have a fuel injector test stand (can be DIY) 3. Even better to have a high speed camera to know what the fuel injector droplets look like. There is little linearity in this and big changes in droplet size, when moving away from the optimum fuel injector signals. I used to have a BOSCH paper on this, just can not find it right now. |
| ELS122:
--- Quote from: Gregg on June 04, 2023, 05:30:27 pm ---It certainly is difficult to out engineer large companies that specialize in trying to gain fuel economy in order to achieve government mandated regulations. But maybe you could consider adding compressed air ahead of the injector to make an air-fuel emulsion similar to the way air bleed orifices worked on carburetors. --- End quote --- A carburator actually does change the fuel particle size depending on the flow by it's nature. Only problem is that you cannot set the minimal particle size, there's nothing to limit the fuel droplets from beading up and splattering all over the intake at low flow velocities. That could be fixed by making the carburator slightly pressurized, and controlling the fuel going to the boosters with a solenoid, sort of like an EFI-Carburator hybrid. But at this point it would be far more practical and versatile to design a new fuel injector that's meant to have varying droplet size. This would also allow you to force a small droplet size for cold starts and/or not require a heated intake manifold because droplet size could just be controlled by a temp sensor right on the injector. |
| ELS122:
--- Quote from: sokoloff on June 11, 2023, 10:08:21 am --- --- Quote from: ELS122 on June 04, 2023, 05:13:44 am ---at 8000rpm, the whole intake cycle happens in around 2 miliseconds, --- End quote --- At 8000 RPM, each cylinder in a four-stroke engine is doing 4000 intake cycles per minute or 67 per second. You also have some valve overlap and intake air flow inertia, so you have nearly an order of magnitude longer than you’ve calculated. --- End quote --- The intake cycle doesnt take 720 degrees of crankshaft rotation to complete, instead it's more around 1/4 of that, 180 degrees. furthermore the injector is PWM'd to control the volume of fuel injected. so it's way faster than 2ms |
| ELS122:
--- Quote from: Miyuki on June 11, 2023, 09:14:25 am --- --- Quote from: joeqsmith on June 04, 2023, 07:57:43 pm ---I wonder how your other valve worked out? I figured for sure you would have got a kick out of the old man's history on it. Hard to argue with his success. https://www.eevblog.com/forum/chat/200hz-air-valve/ At one point, we had a quartz window and laser that we could use to take photos of the patterns. We did whole studies on how the orifice effected it. That's been decades ago and before the piezo injectors. Anything I have worked on was always an on/off type valve. We did work on a multi-pulse system. Basically firing the injectors several times for one combustion cycle. Think of integrating the area under the curve. We could then change the shape of it. It also allowed us to trim individual cylinder. Seems like a whole different life time...... --- End quote --- Thar must be crazy work to do. I know how annoying it can be to just adjust the injection for different types of injectors with different on and off response times. And now with modern piezo-style injectors, multi-injection is something all engines do. --- Quote from: ELS122 on June 05, 2023, 02:48:07 am ---That's the fucking idea. It's amazing how everyone here is unable to understand the question I asked. --- End quote --- Big droplets will always have worse efficiency --- End quote --- >Multi-injection is something all engines do I wonder why when you say: >Big droplets will always have worse efficiency. Must be an oversight of the non-out-engineerable engineers ;D I'll just go and convert my engine to gas vapors because liquid fuel is lower efficiency... you know.. smaller droplets that evaporate faster always mean higher efficiency right :-DD |
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