DI and Diesel injector circuits (for DI use only)

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jharvey
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DI and Diesel injector circuits (for DI use only)

Post by jharvey »

Oh, my. Fred forgets the diesel folks that have stopped by. viewtopic.php?f=42&t=872&start=0&hilit=common+rail

I know several folks that have taken a diesel off the shelf truck, changed the injectors, changed the pistons, found a turbo mounted under the wing of a 747 and bing bang boom, they got 1000hp. Direct injection is starting to take the modified market.

As for direct injection look for the TLE6270 it's hard to obtain if not ordered in qty. The TLE chip should help give a bunch of details what the typical direct injection circuit want's to include. Your specs appear close to me, this chip has an 80V capable drive and lowZ drive, plus a bunch of other nice features. The precise timing is the key issue that most ECU's/EMS's will have trouble with.
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Re: DI and Diesel injector circuits (for DI use only)

Post by Fred »

Actually, Jared, you've forgotten that this EMS is not designed for diesel use as it has completely different and incompatible requirements, so that is out of scope. DI stuff is (possibly) in scope, but certainly wasn't on topic in the ravage thread. Your post was too useful to just delete, so here it is. Please refrain from such behaviour in future though, it's a LOT easier to delete than to move/split. If I'm more short on time, the latter becomes more attractive.
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Re: DI and Diesel injector circuits (for DI use only)

Post by jonr »

Data I have seen shows that direct gas injection has significant HP gains - so it will see increasing use by racing/performance people. Production guys are interested in fuel economy and emissions and it also does well in those categories. IMO, diesel ECU requirements are largely similar and compatible with gas. And the two will start to blend with HCCI and CNG injection (diesel makes a good ignitor). Then there is my personal interest - direct injection of water (for impressive cooling).
Last edited by jonr on Tue Sep 27, 2011 3:03 am, edited 1 time in total.
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Re: DI and Diesel injector circuits (for DI use only)

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I guess I don't see the significant difference between diesel/DI and gas/MI. While I understand your code is currently developed for manifold injection, I see many parts as usable for both types of systems. You have kept quite a bit of flexibility under the hood after all.

In terms of physical hardware, one would need to make a card for the TA card stack or spin a board perhaps a modification of DFH, Puma, or Ravage. It would require removal of the injector and ignition circuits, then most every thing else can stay, RPM, MAP, ect. The removed circuits would have to be replaced by a DI capable circuit.

In terms of software I think to make DI work it would mostly be the addition of a fuel/ignition scheduler section of code. Based on a quick view, I believe the XGate allows the accuracy and resources required, MTX allows loading and logging data such that fuel tables and such can be loaded, and many of the math calcs wold be very similar to what they are now. I think the obstacle to overcome to make it DI capable are small compared to what it's overcome so far.

jonr, if your interested in pursuing DI on FreeEMS, I'd be interested in chatting. I wonder what would be required for the software side of things.
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Re: DI and Diesel injector circuits (for DI use only)

Post by jonr »

I might have to get a new vehicle, but tempting. Have you seen any electric pumps capable of 2000 psi? I might test on a stationary engine. Here is some good info:

http://www.aicit.org/ijei/ppl/09-IJEI8-082002JE.pdf

Others are direct injecting a mix of gasoline and air and getting better atomization and localized lean burn.
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Re: DI and Diesel injector circuits (for DI use only)

Post by Fred »

Jared, diesel requires multiple shots of small duration per cycle in a short time frame, kinda like (good) CDI ignition does. That is more demanding that it appears for a variety of reasons. You're right that a lot could be done with the majority of the existing code. I've got to ask, though, where are you going to get bigger injectors for your DI gasoline engine?
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Re: DI and Diesel injector circuits (for DI use only)

Post by jharvey »

I'm playing with small engines. So if it's possible, the question is, what automotive injector am I using on my small engine. That I don't know yet, as it's not in the realm of possibility for me. If there were software to back it, I'd be interested in giving it a try. GDI would fit in well with the crack pot experiments I want to try.
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Re: DI and Diesel injector circuits (for DI use only)

Post by Fred »

That's all well and good, but the real world use case is a typical automotive engine wanting more power, and that use case requires more injector flow. I don't see aftermarkets selling those things, they're probably not even standardised between manufacturers at all. If someone has a link to aftermarket upgraded DI injectors, post it here! :-)
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Re: DI and Diesel injector circuits (for DI use only)

Post by jharvey »

jonr, That's a good DI read about a modified motorcycle DI. Here are some of my thoughts.

They used a .1ohm sense resistor. That itself creates some really interesting LRC characteristics. For example, the injector being supplied with a 70V supply could very likely see more than 300V at the injector. This fairly small resistor creates a tank circuit, such that you'll see oscillations at the injector, that can resonate and amplify the voltage there, while you won't see it at all at the control circuit. See this post for an article that might be of interest. viewtopic.php?f=35&t=1132

Also they note the measured Ton time of the injector is about .000331 seconds. They made an apparently early design spec decision that they need a bandwidth of about 200kHz, so they couldn't use the low insertion resistance of a hall current sensors because of bandwidth. The Allegro ACS710 goes up to 120kHz +/-12.5A, and the ACS714 does 80kHz +/-5A. So I see the ACS710 being good for around .000008 seconds, which is orders of magnitude better than the Ton time of the injector.

I think the initial design specs could be changed from 200kHz to 120kHz now that there has been some experimentation that indicates that extra 80kHz isn't really required. So the sense resistor could go away, which would lessen the impact of the measurement devices on how the actual device works.

Also they used three discrete PWM signals to control the different currents. As far as I can tell, the 5A pulse, is to limit the overshoot when letting the pintle fall. If one knew the dynamics of the injector a bit better, they could do a much better job controlling the pintle in a PWM PID fashion. I'd like to see a uH measure of the injector as it runs a pulse. That would likely show us an approximate position of the actual pintle, with out actually measuring the physical location of the pintle. For example, when the pintle hits the open physical stop, it stops moving, and there is a blip in the energy absorbed by the injector.

Also also, they appear to have used normal MOSFET's not OVP MOSFET's. They noted the internal freewheel diodes. Those snubber devices expand the error brackets when your letting the field collapse. OVP's are much more linear in the decay, and are much more accurate, not to mention they have a bit faster decay as well. You don't really want a fast MOSFET switching time, you want a fast decay time. I think they chose the normal MOSFET because of the faster switching time, but the snubber device they choose to use creates an ultimately longer response time.

Also also also, the TLE notes the high voltage is only needed for the first pulse. They appear to have used the 70V supply all the time. They would likely get some variations if they only used the 70V for the first pulse.
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Re: DI and Diesel injector circuits (for DI use only)

Post by jonr »

Without going to look, I'd say that the first option to increase max fuel flow in a DI car is to increase fuel pressure. Second is to switch to injectors from the same manufacturer but designed for a larger engine. Both need ECU changes (or replacement :-)).

Let's say that diesel can use multiple pulses for noise control.

No chips yet that handle all the current/voltage control requirements of DI?
Last edited by jonr on Sat Sep 03, 2011 3:04 pm, edited 2 times in total.
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