OE Analogue Temperature Input Sharing

[Motterdude]

Hi all,

I'm new to the forum and will likely be posting frequently from now on since I'll be buying a second-hand M130 GPRP.

I'm reading as much as possible and finding my way around the software but some questions have been popping up. My past experience in the street car world has been with Fueltech and Megasquirt ECUs. I also work for Core Calibration at Stellantis, so there's a decent background with Bosch, Marelli, and in-house control software.

My question now is on sharing input NTC analog temperature sensors.

The way the vehicle sits, I must still share some essentials to keep the car operating as OE. There is no CAN integration with the M130 so far and no plans in the near future due to other priorities.

Given that:

How can I share an analog temperature sensor in the M130 with the OE wiring spliced together? Is selecting the voltage reference to "Absolute" enough or is there another configuration available to turn off the Pull-up resistor? The reason why I ask this is that the OEM ECU still needs access to that data and is spliced together with the current vehicle wiring. I will be sharing both coolant and intake air temperature sensors.

In the Fueltech software, I could check a box and turn off the pull-up resistor. In the MS3X that required me to de-solder a resistor (not something I quite enjoyed doing)

Regarding their transfer curves. I took data using freezing to slowly boiling water using an RTD as a reference temperature measurement and measured the resistance of the sensor.

In the Megasqurit, we use the voltage divider equation and plug-in resistance to get the software read voltage. Fueltech requires a direct voltage calibration with the sensor hooked straight to it. From what I've seen so far I believe that the Motec will require a direct voltage-to-temperature transfer curve (haven't found data anywhere telling me what is the bias resistor's resistance to doing the math with the data I have).Is this a correct mindset or does anyone have information on the internal Bias resistor?

Thank you for the assistance,

[NathanB]

Hi,

The AT inputs on the M1 series of ECU's have a fixed 1k pullup to 5V. If sharing resistive temp sensors with an OE ECU such as in your application, you will need to use AV inputs instead of the AT inputs.

All I/O characteristics are covered in the attached ECU hardware document as found on our website.

We will not be able to provide calibration data for any of the sensors, as we only provide calibrations to suit our hardware setup (1k pullup, as opposed to something like Bosch that uses 3k3)

Selecting the 5V supply rail is so that the sensor reading can have any require ground offsets or voltage compensations applied as required. Absolute just means that the sensor is not getting its supplied voltage from the MoTeC, or in instances where the sensor signal is digital (SENT or CAN)

Our GP packages as setup with a direct voltage to temperature calibration curve. In your instance on shared sensors, as you will need to connect them to AV inputs, the pullup resistor you needs to account for is the one in the factory ECU. Otherwise, all the required information on ECU inputs is in the attached document.

[Motterdude]

Hi Nathan,

That did clear up my doubts.

As my build sits, however, I don't think I'll be able to use analog voltage inputs for that task since I'm already using these out of the 8 avaliable on the M130:

1 Map
2 throttle main
3 throttle track
4 pedal main
5 pedal track
6 oil pressure
7 fuel pressure
8 VR crank position sensor

An E888 module or a C127 dash(I/O Upgrade) may be upgrades I make in the future to get me some additional flexibility with I/O

Seems like, for now, I won't be able to shere these AT inputs with the OE harness then.

Thanks for the document you provided me with.