I've made my own digital WUR

[prebordao]

I’ve been toying with the idea of making a digital WUR for long, for “fun” mostly, but also because the one in my 911 is staying “rich” for too long as the heating element is kaputt.

I had to keep it simple as my fabricator skills and tools are next to non-existent. The breakthrough happened when I had the idea to combine the upper body of a working WUR (containing the diaphragm controlling the pressure) with a controlling system of my own design.

I went with a -011 WUR bought cheaply on Ebay, that probably belonged to an old Audi. The actuator is a small stepper integrated with a worm drive, making it a precise, self-locking linear actuator. I also used a small switch to detect the end of travel for the worm drive, and a thermistor bolted to the assembly (itself bolted to the engine in the usual place) to measure the temperature.

The electronic controller is a very simple design, using a PICAXE18M2 micro-controller and a stepper driver. A serial port is present to allow easy reprogramming. I built it reasonably quick using perfboard and put it inside a diecast enclosure.

Some pictures below:

Controller


WUR baseplate with stepper


Microswitch for detecting end of travel


The complete setup


The modified WUR in place


The controller near the firewall (still to be bolted)


I took it to the road today for the first time, and it looks promising. Cold start was easy, but warm not so.
I still have to play with PvT curves. The beauty of digital is that it's just a matter of tweaking a few variables.

[Targalid]

I am constantly amazed at how brilliant Porsche Pelicans are. Pretty darn clever is all I can say. It looks like your car is Lime Green inside and out.

[prebordao]

Yep, lime green.

[kodioneill]

Nice job how much to make me one? You could add a gauge to help tweaking.

[Danny_Ocean]

It's obvious you have much more time on your hands than I do...and more brains, too.

Nice work! Please update w/progress.

[GaryR]

Looks great! What software do you use to set it, and do you correlate rich/lean condition manually using a separate system w/O2 sensors?

[prebordao]

For setting it up, I tried to "simulate" what the real WUR would do, that is setting a pressure depending on temp sensed.

I have the pressure gauge that PP sells, and that's what I used to tune it. A built-in gauge would be a good idea, but in this way I used the top side of the WUR without any mods.
The actual controlling software is a small program written in Basic. Tweaking involves changing some constants and uploading it again.

Having a simple ECU on board, opens other options. When finished I want to add cold idle control to get rid of the pesky handthrottle !


As for costs, I don't think it went over 200-250 USD.

[Dr J]

Congrats!! Looks great.

[quattrorunner]

sweet!

[prebordao]

I just realized that I probably have the only K-Jetronic equipped car, worthy of the "tronic" part...