Hardiwiring Power for C125

[FoxSTI]

okay.. so question:

based on the diagram below:

http://www.motec.com/aboutpowerdistribu ... noverview/

I can take my car, leave the ECU in place and just remove all the wiring and harnessing, then throw in a PDM and connect motors and switches as needed?

Lights, wipers, windows, etc?

Is the PDM full of transistors and relays?

[the_bluester]

Fitting a PDM is not quite as simple as that but that is the gist of it.

Rather than transistors and relays, it is transistorised switching, monitored and controlled by what amounts to a small computer.

[FoxSTI]

I'd love to put one of those switch panels in my car.

[the_bluester]

Yeah. I tossed up the idea for a long time and went the whole hog, new dash, PDM and 15 switch panel. ECU next year.

The switch panel and CAN interface allows a lot of smarts in the PDM to be used that would otherwise be wasted. The dash is a pretty powerful item but the real brains of the outfit in my case is the PDM.

[FoxSTI]

I know you said the diagram oversimplifies the connection, but let me ask you this.
You said you don't have an ECU yet. Is the car running the factory ECU?

I would like to understand what it entails to out a PDM in a car.

[the_bluester]

I don't have a Motec ECu yet. The Haltech box in my pics is the cars current ECU. It is aftermarket as well obviously, but is getting old and I am up against several inherent limitations of that ECU. It spits out enough data as CAN messages for me to get by for now for dash logger purposes and to play some tricks in the PDM. With a Motec ECU fitted I would be able to do a lot more integration and make better use of information that I can generate in the ECU, dash and PDM than I can at the moment.

To compare to the diagram, as that is shown the ECU is simply powered by the PDM, in my setup (Now and later with a Motec ECU) the ECU is also on the CAN bus, so instead of using a simple input to the PDM taken direct from the ECU such as a thermo fan demand switch, I can have the PDM monitor engine temperature AND speed by the messages the ECU is sending on the CAN bus and disable the fan when road speed is high enough that the electric fan would be of no benefit. That is using the same CAN data that the dashboard would be using to display and or log.

Likewise, I can use the engine RPM message on the CAN bus from the ECU to either do something simple like prevent me from crashing the starter motor by trying to crank it while the engine is already running (By programming a PDM function to detect if the engine is running) or with more complexity, program a momentary button press to then crank the engine until it starts, or with some conditions for safety, to automatically restart the engine in the case of stalling on the start line (My car is track driven only)

Similarly, a gear oil or diff oil temperature sent over the CAN bus by whatever device is monotoring it (My Dash in this case) could be used to have the PDM automatically run oil pumps to circulate oil through coolers when required without the driver being able to forget to do it.

Basically a PDM install can go from being as simple as using it as an electronic fuse and relay replacement with a number of physical switches, up to advanced automatic control of a huge amount of stuff in the car.

[FoxSTI]

Wow, awesome.
I wonder if it could work with a stock ecu.

[Stephen Dean]

You can use them with a stock ECU, however the usability maybe limited due to a lack of information from the ECU, such as engine speed, coolant temp, etc. if you are able to read the CAN Bus data out of the stock ECU, then you could write a custom CAN data set that allows for the data to be used in the PDM.

[FoxSTI]

Sean, I can read some other parameters with my C125 via OBD2, so I am guessing that comes from the CAN.

It makes me wonder why factory cars are just so complicated - why just put a PDM in it from the factory and call it a day.

So I have a Subaru with a C125 and factory ECU. Where do I begin if I want to get a PDM?

[the_bluester]

I suppose this would be more a question for the Motec guys than an answer.

If you are pulling data out of the OBD2 port for the dash, maybe it would be feasible to retransmit that data (Using the Motec template for the video capture system for instance) on the other CAN port of the dash and connect a PDM and maybe keypad to what would amount to a Motec specific CAN bus in an otherwise factory car?

Regards manufacturers fitting PDM type devices, that is actually getting pretty common. My Navara ute has a power control module but it only goes half way as It has fuses in it (Which are not documented in the owners manual) so it is basically amounts to transistorised switching to replace relays.