DI and Diesel injector circuits (for DI use only)

[jonr]

> I am writing my own ...

I think the first word answers my question.

[jharvey]

if you hit that injector open so hard, wouldn't it wear mechanically?

Welcome along.

I agree, that if you smack a normal injector in a fashion like you do with a DI, you might be pounding a nail into a board instead of bouncing a ball off the ground. However, if you calculate how much energy you use before the pintle opens, you can smack it with less energy than what's required required for the pintle to open. Then pause for a slight period of time, then drive normal. For example, from this page. http://sonic.net/~mikebr/ecm_555/inj_inductance.html

At the top highZ scope plot, and at 4mS the you can see the pintle bounce against it's stop. I'm eyeballing .25 amp passed before 4mS. So it's used energy is about E=.5(32mH)(.25^2)=.001j. So the cap charged to 70v would be about 2(.001)/70^2=40.8pF. If you smack it with that to start, you'll rise rapidly. Then pause slightly, allowing the spring to slow the pintle down before it hits. Then drive it normal once it has opened, to keep it open. The key issue is that the injector might not tolerate 70V. So you might want to use a 40V OVP MOSFET instead, which would change the pF calc, and would slow the response time.

Also the backing math is significantly hard to do in software. That's some really accurate timing requirements. The complications are one reason why I like the DMA memory rake approach. You can simply eye ball it instead of dealing with complicated code, or algorithms.

[Fred]

I think the first word answers my question.

Jon, I started this project on the basis that, if required, I was totally capable of building the firmware, the tuning app and the hardware, alone. I, of course, anticipated, hoped, and even expected, that others would like to get involved and help create something great. There is no "I" in Team, my friend, have a look here for more information: http://team.freeems.org

[jonr]

I've done some more thinking about what would be needed for a generic DI driver and have some thoughts about some mosfets, 75V and 12V supplies and a tiny/cheap cpu to do timing and PWM current control. Probably a separate board that would have just one line per injector as input. Diesels have similar requirements although even higher voltages for piezoelectric injectors.

[Srikanth]

I have to say I am very impressed on what all is being discussed now. DI has come a long way here on the forum than my first post here regarding feasibility of implementing common rail. Would it be better to just take apart an injector driver module and examine the guts of it. It might help in clarifying doubts upon hardware, connectors, accuracy etc..

[jharvey]

I've looked into this more, but haven't posted it to the wiki. I'm still interested in DI so I've been making some progress in terms of hardware. Perhaps one day someone can back it with software.

As for hardware, I'm more than willing to help with the concept and design. It sounds like you have hardware available and a willingness to do some testing. Do you have an oscope, injector(s), multi-meter, ect? Can you measure the inductance and DC resistance of your injectors? I'm looking to generate a table that indicates the typical range of an injector, including DI injectors.

Would you be willing to bread board / proto board a test circuit?

Do you know if dry firing a DI injector causes damage?

Where you interested in diesel, or gas DI?

[XR Pilot]

I've looked into this more, but haven't posted it to the wiki. Seems there's no Fred in team, and DI won't be supported by him, as well he seems to be going out of his way to make it harder for other folks to participate in a DI approach. I feel this lack of software support will cause DI to fail with this approach

With all do respect (especially since I'm a "newbie" around here, even though I have been following the project for a while) but this seems a bit harsh.

How about if I say "DI is not something that I plan to support" which is very different from "DI is something that I plan to not support". I say the former. I will not be doing any work on anything that does not benefit the majority of the forseeable and current user bases until everyone running it or trying to is happy. Once all the core work is done, sure, anything is possible.

To me this seems pretty clear that Fred isn't discouraging DI work, he just isn't making it a priority at the moment. To me this is perfectly acceptable as Free-EMS firmware still has a long way to go to be able to stand on even footing with most aftermarket ems' in feature set at this point in time. Whilst DI is certainly an interesting technology (even from a performance perspective) I think you need to crawl before you can walk.. I'd be particularly careful about going down the road of controlling a common rail diesel, you would want to make sure your timing is pretty damn accurate. Coming from someone who has heard diesel knock before, it's not a pleasant sound

My 2 cents.

[jonr]

Toyota diesels have something called the EDU that sits between the ECU and the injectors. Anyone know more about this? It could be what is needed in terms of drive circuit.

[Srikanth]

@jharvey yes I do have access to a multimeter, oscope etc will try scoping some bosch or delphi common rail injectors as they are mode widely available than denso. I am willing to bread board if I can find the time. Am sorry to say that I can cannot give any firm commitments due to my work schedule.

As for dry firing a DI injector well the fuel is what cools it, and for common rail injectors they will not work without a fluid. You control a secondary hydraulic circuit which in turn controls the primary hydraulic circuit. In other word dry firing will not cause the nozzle needle to lift, it would only actuate the secondary spill pintle.

I happened to be interested in both Gas and common rail as they are the future. Let me try procuring some Gas and common rail injectors.

@jonr The EDU is the driver box for the injectors. Common rail injectors use high amperage draws and boosted voltages which the main ecu is not capable of handling. Thus the main ECU drives the EDU which inturn drives the injectors. The EDU heats up quite a bit and are usually cooled by diesel fuel.

[jharvey]

@jharvey yes I do have access to a multimeter, oscope etc will try scoping some bosch or delphi common rail injectors as they are mode widely available than denso.

Cool keep me posted.

As for dry firing a DI injector well the fuel is what cools it, and for common rail injectors they will not work without a fluid. You control a secondary hydraulic circuit which in turn controls the primary hydraulic circuit.

That sounds similar to what I'm more familiar with in hydraulic and pneumatic land, we call it pilot operated. It makes sense that they do that kind of power amplification.

I happened to be interested in both Gas and common rail as they are the future. Let me try procuring some Gas and common rail injectors.

Let me know if you find some reasonably price stuff. Most of what I've seen is a bit pricey.