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Connecting to CANBUS instruments


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Hi all

I'm new here so please accept my apologies if I am doing something wrong or in the wrong place, I have tried the search method but cannot find anything.....

I have a project underway, I have a Storm G4+ (still in the box at this stage!) which will run a BMW M70 V12. The physical engine installation is well under way so I am starting to consider wiring,  instruments etc.

 If I provide a digital speed input to the ECU, will I be able to configure the ECU to drive a CANBUS dash from something like a VW Golf? (I am looking primarily for speedo and tacho function) And if so, whilst the dash donor car would have had 5 cylinders, as the CANBUS drives the tacho presumably it will read the digital engine speed data which would not have reference to number of cylinders?

Or am I being naive and it is not that simple?



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It should be doable.  We have pre-configured CAN streams in the ecu for VW golf and Audi TT so one of those options seems to work with most VAG dashes.  If you used a dash from some other car that we didn’t have the stream preconfigured for then you would need information about the CAN message ID and format to be able to make it work.

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The tacho and speedo signal is that simple - the ECU simply sends something like "tacho = 3500rpm, speed = 40kph" and this gets displayed on the dash so cylinder count etc is not an issue.

There is a huge additional thing you need to figure out first though.... while the canbus protocol is standard, what each manufacturer sends on it is not standardised. eg some of them will multiply tacho/speedo/other values by 100 before sending them out to allow more granularity in the numbers sent (cant directly do decimal points). You will need to somehow map out what signals the dash is expecting to see - it will expect certain signals to come from certain other devices on the canbus network - you need to know the ID of these devices so you can emulate it, and you need to understand what the values are so you can make the ECU put the right numbers in the right format in the right location within each data packet. Usually you would do this by sniffing the canbus from the live vehicle before you pull out the dash.

Is this dash original in your car? if so, some of the signals may be coming from other devices - eg speed is commonly from the ABS ECU, not the engine ECU. In this case you would likely have the engine ECU receiving it via canbus as well rather than transmitting it.

The VW canbus specs may be availilble for some vehicles and if you can find this and a dash for the same car you would save yourself a lot of work. [edit] from Adam's post at the same time, it seems a lot of the VW canbus specs are are already avilable in the link ecu's so 90% of the work is already done.


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Thank you Adamw and cj for your very informative and helpful reply. The dash is not original to the vehicle (it is a milk float...) but it seems that it can probably be made to work. When I get a bit further down the line I will let you know how I get on.

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