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Just dropping in to say a huge thank you for all of the tuning information, guide, chip info, XDFs, and BINs - I was able to decode what this Max DME III chip was actually doing and I was able to successfully program a PicoRom EEPROM emulator with a custom tune to start dialing in my modified 944 Turbo! This is turning into a really fun, and meaningful, project for this web engineer.
Next steps are getting an analog-to-digital DAQ so that I can start gathering data and telemetry from the car and wideband while tuning it.
For background, I got started down this bit of a rabbit hole because I blew the head gasket on track at Road America last year and thought it might have something to do with the combination of unknown chip, aftermarket mods, and lower octane gas the 2nd day causing knock. After looking at the timing advance and fueling maps in this aftermarket chip, I was getting away with it. Now, I'll be able to really dial in the setup for reliability and power.
PXL_20260303_141629231.jpg (4.51 MiB) Viewed 326 times
PXL_20260306_205711429 (1).jpg (1.82 MiB) Viewed 326 times
pizatski wrote: Fri Mar 06, 2026 1:15 pm
Just dropping in to say a huge thank you for all of the tuning information, guide, chip info, XDFs, and BINs - I was able to decode what this Max DME III chip was actually doing and I was able to successfully program a PicoRom EEPROM emulator with a custom tune to start dialing in my modified 944 Turbo! This is turning into a really fun, and meaningful, project for this web engineer.
Next steps are getting an analog-to-digital DAQ so that I can start gathering data and telemetry from the car and wideband while tuning it.
For background, I got started down this bit of a rabbit hole because I blew the head gasket on track at Road America last year and thought it might have something to do with the combination of unknown chip, aftermarket mods, and lower octane gas the 2nd day causing knock. After looking at the timing advance and fueling maps in this aftermarket chip, I was getting away with it. Now, I'll be able to really dial in the setup for reliability and power.
PXL_20260303_141629231.jpg
PXL_20260306_205711429 (1).jpg
Awesome -- once you have access to the maps like that, you'll never go back to off-the-shelf chips! Does that emulator work with TunerPro RT to allow for real-time map edits?
Awesome -- once you have access to the maps like that, you'll never go back to off-the-shelf chips! Does that emulator work with TunerPro RT to allow for real-time map edits?
Thanks, Tom. I agree completely - I won't be going back.
The emulator doesn't work natively with TunerPro RT, but it does have a fairly simple command line interface. The workflow looks something like this:
1) Install pre-requisites (TunerPro or TunerPro RT) and the picorom CLI
2) Open the appropriate BIN in TunerPro with the appropriate XDF (in my case, the 28 pin configuration)
3) Make changes, save them
4) Use the picorom CLI in the command line tool of your choice (Powershell for me) to upload the BIN you just modified to the picorom in 64kbit mode which is what the DME expects
5) Test on road or dyno, continue modifying tune as needed
6) Commit it to the onboard flash if you want it to persist after the picorom is powered off
Steps 2 - 5 can be done with the car running and the laptop connected to the picorom while installed in the DME. When updated, changes take effect immediately in the car so you can tune on the fly. When committing to flash, the chip is power-cycled and the car shuts down so that's more of a last step after tuning session type thing to live with what you just did until you burn an EEPROM.
I haven't dug into it much, but I'd imagine it wouldn't be too difficult to make a plugin or script with TunerPro which would upload to the picorom upon save immediately.
Meine44 wrote: Wed Jun 24, 2026 10:40 am
These DIY chips are very intriguing. I wonder if this would be the best route to update my Autothority MAF that came on my 1988 951 when I bought it.
What is the best way to read the Autothority chip to get a baseline of the current tune?
Does the TunerPro RT software require a laptop to be plugged in as the car is driven in order to log real-time data?
Autothority moved the map locations around on its normal performance chips, so I'd image they did the same on their MAF chip. As such, the XDF files available here (and elsewhere) won't work for any map that's been moved. It's not impossible to find them, but you'd need to spend time hunting down the maps of interest and building your own XDF file for it. Or ditch the APE MAF and go back to the AFM or MAF that uses more standard chips.
Interesting the mention of the "Autothority MAF " I didn't realise that such a thing existed. I have just posted details of a project I have been working on viewtopic.php?t=5337
Maybe I should have searched to see if such a product already existed. Regardless, it was an interesting project and things like that keep me busy in retirement.
