VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => TDI Engine -General Info => Topic started by: Toby on April 12, 2014, 03:43:58 am
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Has anyone come up with a simple electronic VNT controller? I remember some discussions somewhere about how simple it would be to do. I think I want to put a VNT on my AAZ in the near future. Is ROR still playing with one or did he get a new GF and fall off the end of the world?
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vanbcguy is making one. It starts with the audrino and then you have to build the rest of it with other stuff. See his build thread in this TDI section.
ROR went manual, and I am sure he never got a new GF but did fall off of here.
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This is what I've used as my inspiration / base code:
http://dmn.kuulalaakeri.org/vnt-lda/
I've changed a few things - I added an input for my EGT probe and I've modified the code so the LDA is basically operating as it would on a regular mechanical engine, but the controller can reduce or completely cut boost to the LDA if EGTs get high. This of course in turn reduces fueling, reducing EGTs. Built in safety system. :)
He's actually got a full ECM that can run an AHU/ALH electronic pump using an arduino too. That's an awfully tempting way to go - the flexibility of electronic controls in terms of being able to modify maps and things without the proprietary limitations in the VW ECM. Actually I should look at how he's done timing - I do have a needle lift sensor that's not doing anything otherwise... Would be cool if I can use it! Being able to measure dynamic timing would be pretty rad.
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Are you at the level of "inspiration" or functional prototype?
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Functional prototype. It is operable but has only been bench tested thus far since my car wasn't ready yet.
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What are you using for inputs besides rpm and TPS? MAP? How are you doing the RPM input? W wire of something fancy?
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For RPM I'm using the factory crank position sensor on my AHU block. I just discovered yesterday that it needs a little conversion circuit to be able to talk to the Arduino - I have the bits coming for that.
Other inputs:
- EGT - I'm feeding my EGT probe to the Arduino so it displays EGTs on the same LCD as everything else. High EGTs cause the backlight of the LCD to change from green under normal conditions to orange and then finally blood red as you approach the limits. The system also starts reducing boost seen by the LDA under high EGT conditions, but otherwise it lets the LDA operate normally
- Intake Manifold Pressure - Not 'absolute' pressure like a true automotive MAP sensor (they are adjusting for changes in altitude and barometric pressure as well as turbo boost pressure) but yes, we need a boost signal to control the turbo
- Exhaust Manifold Pressure - I'm reading in EMP and displaying it on the LCD, however I'm not doing anything programatically with this data. I intend to use it more for tuning the VNT than anything, but EMP gauges are generally unreliable due to all the contaminants in exhaust. So since I expect it to break at some point I am displaying it and have the ability to log it but I'm not taking any action based on it.
- Intake Air Temperature - I have an IAT sensor, I am displaying IATs next to EGTs purely for informational purposes. Again I am not doing anything with the data other than displaying it and potentially logging it.
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No TPS input? How does it know if you are at WOT or cruise?
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Yes, TPS too. You asked what I had besides TPS and RPM. ;-)
I'm using an injection pump from a Land Rover Discovery 300TDI that would have had EGR. The pumps for those applications have a built in TPS that would talk to the EGR system.
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I see you're using a integrated VNT on your AAZ; here's how I did it on my 1.6 IDI:
I bought approx $75 worth of stuff from McMaster and $15 for two throttle arms from Speedway Motors
and then built a mechanical linkage based on Libbydiesel designs.
Picture 1 is the adjustable length rod + VNT actuator can with flipped internals to work on boost pressure instead
of vacuum, and it has a custom spring from Libbydiesel that was selected to work with a maximum boost of 20psi.
Picture 2 shows the linkage that takes the motion of the pump throttle and arm in picture 1 and directs it 90
degrees to the vane actuator on the turbo housing. (I'm in Seattle as well)
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picture 1 was missing...
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How are you planning on supporting all of that stuff. If it is not very well triangulated and pretty stout, it will shake itself to bits in short order.