CAN BUS question for the Gurus out there

[djwarner]

For those familiar with the J1979 standard.

 

I am transplanting a 2012 Chevy LFX engine into a 2011 Miata. (could find a reasonable Z transplant candidate).

 

Since I have a post 2008 CAN BUS devices, I am wondering if I could connect the ECU CAN BUS signals into the Mazda CAN BUS to drive the instrument cluster?

 

From what I know about CAN BUS the basic performance parameters are polled using a standard prefix and a standard bus protocol. Other manufacturer specific data points would not be polled, but they shouldn't be needed to run the instrument cluster gauges.

 

There would be several advantages in using the Mazda Cluster rather than replacing it with Speed Hut CAN BUS gauges. Besides limited space available in the Miata, there are some 12 indicator lights for non engine functions that would have to be replaced with the Speed Hut Gauge package.

 

The Camaro gauges can't be used because the Body Control Module converts the high speed bus from the ECU into a medium speed bus that feeds the Instrument Clusters. The Miata however, drives the instrument cluster directly from the CAN BUS.

 

How feasible is this?

[Richard Oben]

NOT an expert by any means.  My only thought is if the voltages match up then you are fine with making the connection but I doubt they will be.  It would probably take the factory service manual from both cars with complete, I mean very complete wiring diagrams to see if it is even feasible.  JMHO,  The guys at LS1Tech may be off more help.  Richard. 

[djwarner]

The only physical connections required are a CAN BUS High, CAN BUS Low, CAN BUS Ground. The voltages on the CAN BUS are all standardized.

[winstonusmc]

Its feasible if you use something to translate the CANBus. For example, I have an Arduino translating the fan output signal from Megasquirt into a Nissan Intelligent Power Distribution Module (IPDM) that runs the fan from under the hood. It just receives the CAN word from the Megasquirt and re broadcasts it out on the correct word for the IPDM. The only thing is you will have to decode the CAN word the has the gauge cluster info for both the Miata and the ECU, which would need to be done in a running setup. I "Sniffed" my CAN in my G35 to find out what went where. Just Google "CAN Bus Sniffing". 

[TimZ]

For those familiar with the J1979 standard.

 

I am transplanting a 2012 Chevy LFX engine into a 2011 Miata. (could find a reasonable Z transplant candidate).

 

Since I have a post 2008 CAN BUS devices, I am wondering if I could connect the ECU CAN BUS signals into the Mazda CAN BUS to drive the instrument cluster?

 

From what I know about CAN BUS the basic performance parameters are polled using a standard prefix and a standard bus protocol. Other manufacturer specific data points would not be polled, but they shouldn't be needed to run the instrument cluster gauges.

 

There would be several advantages in using the Mazda Cluster rather than replacing it with Speed Hut CAN BUS gauges. Besides limited space available in the Miata, there are some 12 indicator lights for non engine functions that would have to be replaced with the Speed Hut Gauge package.

 

The Camaro gauges can't be used because the Body Control Module converts the high speed bus from the ECU into a medium speed bus that feeds the Instrument Clusters. The Miata however, drives the instrument cluster directly from the CAN BUS.

 

How feasible is this?

If the two busses are the same data rate ("high" speed can still be either 500k or 1Mbaud) AND both only need messages in the standard OBD-II message set, then this might work.  The problem that I would look out for would be if both modules are normally on their respective vehicle's main high speed bus, then there are almost certainly other proprietary messages being used by both, and if any of them happen to be on the same message ID it will likely crash the bus.

Edited April 10, 2016 by TimZ

[djwarner]

Fitting for as simple a vehicle as a Miata, the CAN BUS is a fairly simple single high speed bus. Since my transplant vehicle does not have Dynamic Stability Control or Advanced Key Locks, The only control modules are: the Engine Control, Transmission Control, Instrument Cluster, ABS Brake Control  and Hard Top Control.

 

The Instrument Cluster receives Vehicle Speed, RPM, Engine Coolant Temp, Odometer, Fuel Injection Amount from the ECU.

It Receives Transmssion Gear Selection info from the TCU.

 

It also receives indicator status for MIL, Generator Warning, Cruise Control Status, Brake System Warning, ABS Warning, Power Retractable Hard Top Warning, AT Malfunction Warning,

 

It outputs Fuel Level to the ECU. It exchanges Immobilizer signals with the ECU.