Getting an electronic fuel injector to only open partially - Page 1
Forum section: electronics / general

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: June 04, 2023, 04:16:06 am
content: How do I make a gasoline fuel injector open partially? I tried just undervolting one but no matter what I tried it would just be either fully open or fully closed.Maybe using high frequency AC with a DC offset? Maybe there's a specific type of injector that allows this?The reason I want this is to be able to adjust the fuel particle size on-the-go. To maximize engine efficiency over the entire rpm range.I'm not very concerned about the impact of fuel flow when the injector is partially open, since I can compensate for that later and I just want something that gives me an adjustable particle size first.

author: bdunham7
author_rank: Super Contributor
timestamp: June 04, 2023, 04:39:01 am
content: Quote from: ELS122 on June 04, 2023, 04:16:06 amWhat effect on fuel droplet size do you anticipate from various pintle positions? I'm just curious...As for hanging a solenoid valve in an intermediate position, I think it would be pretty tricky. You would have to do something like using a PWM signal and then somehow measuring the pintle position (via a change in inductance) in between the pulses using some sort of test signal. Or something like that. I don't think typical port injector changes inductance much during the intermediate phase that you are looking to stabilize, so...

author: AndyBeez
author_rank: Frequent Contributor
timestamp: June 04, 2023, 08:43:34 am
content: What kind of fuel injection are you trying to modify - direct cylinder or manifold are common 'modes' of injection.https://en.m.wikipedia.org/wiki/Manifold_injectionhttps://en.m.wikipedia.org/wiki/Petrol_direct_injectionhttps://en.m.wikipedia.org/wiki/Common_railLots of options. EFIs are often optimised to the mechanics, at great expense to the engine manufacturers.

author: Alti
author_rank: Frequent Contributor
timestamp: June 04, 2023, 09:22:30 am
content: You could control fuel pressure according to rpm-s.This should be fast and easy, just put an electronically controlled bypass valve.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: June 04, 2023, 09:50:58 am
content: Quote from: Alti on June 04, 2023, 09:22:30 amI remember the bill of a german study office (with a black horse in the center of the crest) that was around 60 gigabucks in order to implement a Bosch injection system on an french motor.It was just a injection upgrade on a existing motor.

author: JPortici
author_rank: Super Contributor
timestamp: June 04, 2023, 11:07:06 am
content: Quote from: ELS122 on June 04, 2023, 10:51:20 amDenso has as system in which the fuel pressure sensor is directly at the injector, one for each injector. They do it to calculate the quantity of fuel going in the chamber with greater precision. It's for diesel engines, marketed with the name iART.Also for diesels, mantaining open/ partial opening is achieved via PWM. Injector is first fully opened as fast as possible (high current) then the current to the valve is modulated. But i don't know about gasoline as we usually just ignore the fuel injectors

author: langwadt
author_rank: Super Contributor
timestamp: June 04, 2023, 01:02:36 pm
content: Quote from: ELS122 on June 04, 2023, 05:13:44 amwhat type of injectors is that? direct injection gasoline?, they are surely not the usual injectors used in port injection gasoline engines

author: mendip_discovery
author_rank: Super Contributor
timestamp: June 04, 2023, 01:38:00 pm
content: I dont have my usual contact to ask about this (ford fuel injection nerd).But my 2p, it takes a given time to open completely could you only pulse long enough for it to open a small amount. Even dropping the current so it opens slower.Alternative idea is to add some extra smaller injector for the lower speeds and swapping over to larger ones.

author: bdunham7
author_rank: Super Contributor
timestamp: June 04, 2023, 02:02:39 pm
content: Quote from: ELS122 on June 04, 2023, 05:13:44 amYou're making a lot of assumptions that you should consider more carefully. There are a lot of different specific types of injectors and they all have different designs and drive requirements. I'm pretty sure that there are many that will behave pretty much the opposite of your stated expectation. Also, not that it matters to your original question, but the injector on-time is typically not correlated with the 'intake cycle'; the specifics of that are the subject of quite a bit of research and testing when an engine is designed.

author: Gregg
author_rank: Super Contributor
timestamp: June 04, 2023, 05:30:27 pm
content: 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.

author: Miyuki
author_rank: Frequent Contributor
timestamp: June 04, 2023, 06:26:21 pm
content: Most fuel injectors are not spraying from the needle but from an array of tiny precisely machined orifices in a plate on its tipOpening the valve just partially will decrease the spray pressure, so it will just make big dropletsSuch ancient injector construction was used on throttle body injector with very low pressure spraying at the throttle plate and just evaporating the fuel in the long intake manifold

author: joeqsmith
author_rank: Super Contributor
timestamp: June 04, 2023, 07:57:43 pm
content: 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......

author: bdunham7
author_rank: Super Contributor
timestamp: June 05, 2023, 03:07:10 am
content: Quote from: ELS122 on June 05, 2023, 02:48:07 amPerhaps you don't understand the question you asked since you seem to be stating it backwards.Quote from: ELS122 on June 04, 2023, 05:13:44 am

author: TERRA Operative
author_rank: Super Contributor
timestamp: June 05, 2023, 11:26:42 am
content: Injectors are optimised to spray correctly at a certain fuel pressure range.Altering the pintle position when open will affect the pressure of the fuel exiting the valve portion of the injector before it hits the director plate that actually determines spray pattern and droplet size. Less open pintle = less flow = less pressure at the plate and sub-optimal spray pattern.Also, the injectors in a manifold injection system don't actually spray directly into the open combustion chamber anyway, they spray onto the back of the intake valves to help keep them cool and to evaporate the fuel for better atomization.My thinking to increase atomization would be to increase fuel pressure then decrease the injector on-time to compensate for correct air/fuel ratios.But before diving into injector droplet size, I'd be doing more 'tried and true' methods of increasing efficiency and power, like forced induction, porting and polishing the intake system, flow matching the intake and exhaust ports, adjusting intake and exhaust runner lengths to optimise the powerband for the application at hand and designing the exhaust system to scavenge at the same RPM range.Then use an aftermarket ECU to tune the car to a better/leaner tune on a dyno instead of relying on an overly conservative OEM tune.

author: Miyuki
author_rank: Frequent Contributor
timestamp: June 11, 2023, 09:14:25 am
content: Quote from: joeqsmith on June 04, 2023, 07:57:43 pmThar 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 amBig droplets will always have worse efficiency

author: sokoloff
author_rank: Super Contributor
timestamp: June 11, 2023, 10:08:21 am
content: Quote from: ELS122 on June 04, 2023, 05:13:44 amAt 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.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 11, 2023, 10:20:07 am
content: 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.

author: bdunham7
author_rank: Super Contributor
timestamp: June 12, 2023, 03:25:13 pm
content: Quote from: ELS122 on June 12, 2023, 01:53:03 pmHaving an idea is nice, but you keep mistating the fundamentals of what you are discussing. Assuming we are talking about a conventional-ish multiport electronic fuel injection system with typical pintle-valve injectors, not a single-point, central, mechanical, direct injection or a MPI/GDI hybrid (all of which exist) then you should observe the following:The 'intake cycle' is not really relevant to the discussion. During normal cruise, a typical MPI gasoline engine often turns the injectors on during theexhaust stroke. This may vary widely with temperature, load and engine design.During high-load high-RPM operation, the duty cycle of the injectors may exceed 80%, or 576 degrees.Typical PWM injector drives use an inital current to open the injector and then a PWM current to control the current and keep the injector open, not pulse it or hold it partially open.There have been a huge number of variations tried and produced over the years, so if you want specific answers you have to be discussing a specific system. Finding a solution to your issue would most likely be realized by tracking down the right injector(s). Using two different injectors also might be something to think about. If you want to 'out-engineer the engineers', start by learning what they've already tried and done.QuoteTo an extent the statement is actually true--evaporating the fuel before it gets in the cylinder (using waste heat) improves the overall thermal efficiency of the engine. This may come at the price of reduction in power density, emissions issues and other things I can't think of right now.

author: CaptDon
author_rank: Super Contributor
timestamp: June 13, 2023, 01:30:49 pm
content: After working on engine ECU's for the last 10 years, and having experience with many types of injectors including 'one-off' trial designs from big boys like Bosch the 'partially open' type only work (as another poster clearly stated) in the older style throttle body low pressure injection scheme. In the medium high pressure systems (60 to 100psi) a partially open injector produces poor atomization NOT BETTER. As another poster already stated RAISING THE FUEL PRESSURE and shortening the duty cycle is the correct answer and is why you now see injection systems running very high pressure which leads to some spectacular fires from the mist created by very tiny pinhole leaks or loose fittings. Injection systems today can produce such a fine mist in the intake manifold that it looks like fog. B.T.W., you never 'polish' intake runners and ports thus causing 'wet flow' issues where the particles come out of suspension and wet flow along the runners. The best designs look like they are 'parkerized' with a dull finish and often acid is used to obtain the dull finish appearance. There was a design study done about 40 years ago with carbuereted engines where a 4" diameter piezo ultrasonic driven disc was built into the floor of the intake manifold directly under the carb. It worked so well that when activated the engine ran excessively rich and the air fuel mixture had to be leaned out. The BSHP vs. the fuel consumption increased by about 20%. No 'drivable' control system was ever developed for street use sadly. Also as stated, to get enough fuel injected during high horsepower output the injection cycle starts long before the intake valve opens for port injected engines and easily can go to 80% of the 720 degree engine cycle.

author: HighVoltage
author_rank: Super Contributor
timestamp: June 13, 2023, 01:44:47 pm
content: Quote from: CaptDon on June 13, 2023, 01:30:49 pmActually BOSCH Germany did develop such system for the OEM and promoted it at a conference in the 1980s. I had the luxury to drive such a prototype car but the automotive world did not implemented it for production.This ultra sonic system was the best fuel atomization at the time. But today's high pressure fuel injectors are much better.