openinverter forum

Hi Folks,
I started this project about 3 years ago when I first bought a 2008 Porsche Cayman S Tiptronic with bore scoring. I acquired a standard LDU used from someone that was going to put this into their 996 project but realized it couldn’t fit. He had already purchased an openinverter interface board with connectors setup and a Gen2 Charger with interface card. I also bought the following elements:
- Chevy Volt Gen 1 battery pack
- F1Moto LDU mouting frame/kit.
- Tesla DC-DC converter
- Tesla Model S Gen 2 AC compressor
- Vauxhaul electric power steering pump
- Audi brake vacuum pump/dracarys vacuum switch
- Vero BMS

I’ve heavily relied on Boxster EV’s build thread converting his 986-based Boxster using pretty much the same setup that he used, so I won’t go into too many details. I’d also like to thank many of you that have helped me with debugging or educating me on how to get the above systems to work together at a basic level where I can start the car, drive, stop and charge it.

There’s a more “mechanically” focused build thread I started where I captured pics and process for disassembly here

I've also had other posts on this forum to get help on debugging various issues if you search my username.

My next phase is to connect the AC compressor and control it using CAN control, integrate the HV PTC heater (HV is connected, but through a contactor that I'm trying to figure out how to control), and integrate the LDU CAN BUS to the Porsche Drive CAN BUS. I will try to do a better job of documenting/sharing as I go in the event someone else is trying this and can be helped or can help. I'll also try to include some additional pics of my setup, but again honestly much of it is almost identical to Boxster EV. I even bought my trunk-mounted battery box from an extra one he was selling!

Here's my approach:
1. I've removed the DME from the car. I had to disconnect the cooling water control power connector located at the passenger-side front radiator accessible from the wheel well. This is because if the DME is not connected when the ignition turns on, the radiator cooling fans automatically go to high speed as a fail-safe measure when they don't receive a coolant temperature from the DME.
2. I've created a "VCU" that contains an arduino processor connected to two MCP2515 CAN transceivers, one connected to the Porsche Drive CAN and the other connected to the Tesla LDU CAN wires. So this unit will be able to mimic the engine and transmission inputs from the LDU to the Porsche and potentially vice versa to enable ABS, PSM, PASM and even climate control properly. This unit will sit where the previous DME used to be mounted.
3. I've also created a secondary "VCU" located behind/underneath the HVAC control panel at the front that will control the AC compressor because the one I have you can only do via CAN messaging.

I'm making these assumptions of exactly which signals/messages need to be communicated back and forth:
From Arduino to Porsche:
- TCU hearbeat signal

From LDU to Porsche:
- Gear position indicator (Reverse, Drive, Park) to update the instrument cluster lights.
- Engine RPM (will need to cut in half as the LDU has ~16000rpm vs ~7300rpm for the porsche)
- Coolant temp - will take this from the inverter or stator temp.
- Actual torque - LDU's current draw or torque output

From Porsche to LDU:
- Already wiring the accelerator pedal signal, 5V and ground wires directly to the LDU (not via CAN)
- Brake switch is also wired directly to the LDU
- Already mounted contact sensors to the gear selector to indicate P, R, D wired directly to the LDU
- Torque reduction request from PSM to LDU via CAN. Not sure if this can work on top of the hardwire accelerator pedal inputs, but to be tested.

Hopefully all of this, when connected will address all the warning lights I'm seeing on the dash that I current just ignore. As it sits, the ABS shows an error and does not kick in when stopping quickly. I'm assuming the PASM, PSM also doesn't work and I can confirm the climate control doesn't work. Time to start recording and spoofing!

Here's a pic of my DME replacement "VCU".... with about 6 hrs of 3D printing and ~$20 of parts from Amazon with a whole bunch of Gemini trial and experimentation that will go in the car.....

Thanks for this post. I'm helping a friend with the electronics/software in his 996 conversion and am super interested in anything you can share about talking to the remaining electronics in the car with the DME removed. Will your code be open-source?

Yes that would be the intention. Just to note, there's a few minor differences I'm told between the 996/986 vs 997/987 platforms including the amount of controls and information that was done through CAN vs directly. Most of what I'm doing is again through Gemini, but I'll certainly be posting the steps and code if it helps.

Yeah, I realize that after I posted. Thank you though, I'm sure you experience will be helpful to me and others.