Fuel Injector Voltage Questions

pysical

Sergeant
Jun 16, 2017
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2009 335xi E90
Can anyone give me some information on these injectors. I am looking into building something (hopefully) that can match up PI injectors with the direct injectors.

From my reading the injectors are a Piezo type which uses 100+ volts to charge up plates to make the fuel flow. Does that mean the 100+ volts are going through the wire harness to the injector? Is it a constant 100v+ or does it pulse that when it needs to open?

Trying to find a way to gather the pulses and convert them into a lower voltage to power the PI injectors. I have been looking into using a Arduino to do this since I have programming experience this should be fun. Just looking for information if anyone has anything. Or some ideas on how to implement this a easier way.
 

NoQuarter

Major
Nov 24, 2017
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Considering how fast the injector on cycle is what do you consider pulsing?

Pulsing during the ms time the injector is on?
 

pysical

Sergeant
Jun 16, 2017
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2009 335xi E90
By pulse I mean on/off/on/off/etc. I want to be able to capture the pulse of the injectors and convert to a low impedance style injector (pi).
 

LamboLover

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Apr 6, 2017
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Can anyone give me some information on these injectors. I am looking into building something (hopefully) that can match up PI injectors with the direct injectors.

From my reading the injectors are a Piezo type which uses 100+ volts to charge up plates to make the fuel flow. Does that mean the 100+ volts are going through the wire harness to the injector? Is it a constant 100v+ or does it pulse that when it needs to open?

Trying to find a way to gather the pulses and convert them into a lower voltage to power the PI injectors. I have been looking into using a Arduino to do this since I have programming experience this should be fun. Just looking for information if anyone has anything. Or some ideas on how to implement this a easier way.

https://www.picoauto.com/library/automotive-guided-tests/piezo-current/

The waveforms, multiple injections, short pulse widths, current control along with the phasing difference between PI and DI will give you headaches.

I am thinking of something for N55/S55 but using CAN bus and crank pulse trigger from the DME on the back of another project that already has hardware on the CAN bus, some spare I/O and a way of getting variables out the DME with low latency, but I still have the problem of needing to know the DI pulse length before it happens to control PI correctly.

I don't like Arduino - maybe you have a way around the limitations, but the IDE and debugging, lack of multiple source files and unnecessarily different terminology to try to simplify things didn't work for me - back to Notepad++ and GCC on the command line for me - compiles faster, code is smaller, no weird stuff behind my back to try to make it simple.

For a project like this you would end up writing or modifying libraries as you will find all sorts of issues with ones that people are using for less demanding applications.

For reading waveforms and outputting pulses you will want to use the chip's hardware directly, not abstracted and inefficient software tasks designed around an 8 bit AVR.

I've already had to rewrite pulse acquisition, CAN and Websockets libraries and tweak FreeRTOS settings to get low latency on my project. I didn't hope for all that complication, and neither will you I expect?
 
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bahn

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Nov 5, 2016
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I'm doing some scope work tonight on the ignition side, if I have time I'll put the Rigol on the injectors for you. I'm assuming you're talking about making your own PI controller? You'll need a crank trigger signal for timing as the SOI and EOI event timings are different for DI vs PI.
 

jyamona

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Nov 7, 2016
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Would you all feel more comfortable if spark cut was linked to DI cut on a per cyl basis? This wouldn't be too difficult to do, just bitwise OR of the two inhibit masks. This would make current AIC boxes safer, along with simplifying the design work required to make a "safe" sequential injection controller if one wished.
 

bahn

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Would you all feel more comfortable if spark cut was linked to DI cut on a per cyl basis? This wouldn't be too difficult to do, just bitwise OR of the two inhibit masks. This would make current AIC boxes safer, along with simplifying the design work required to make a "safe" sequential injection controller if one wished.
This is honestly the best solution towards making the AIC's safer. You're the man Jake.
 
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bahn

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Nov 5, 2016
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Cheers, if you need more testing let me know and I'd be more than happy to test as well. For the sake of answering the original question in this post I'll still try to get my scope on it tonight.
 

pysical

Sergeant
Jun 16, 2017
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2009 335xi E90
Well I am glad others are looking into this as well. I have some programming knowledge so I can help in that if anyone needs help. Until then I am going to continue to do some research. It does seem like a lot to handle so jyamona brought up a good point. Hopefully we can get something out of that.
 

bahn

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Nov 5, 2016
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Looks like right around 150V. Channel 2 (blue) is a direct back-probe of the injector terminal with a 10:1 attenuation (configured on the scope). Channel 3 (purple/pink) is from a inductive capacitance probe for verification (attenuated and not configured on the scope). Would have added my current clamp into it but I left it on by accident and the 9V battery is dead :(
NewFile7.png
 

V8bait

Sergeant
Nov 2, 2016
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Texas
Some scope pics of factory injectors courtesy of Robert if you're interested

Yellow is CPS notice missing tooth, blue is injector (positive open, negative close), Green/Purple are cams

None of the measurements are calibrated this was purely for visualization if it helps anybody.

22237147_10212500915951461_308569997_n.png
22264491_10212500924351671_1234136785_n.png
22290117_10212500930391822_1732071508_n.png
 
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