Can bus cable lengths?

[Funkyflynz]

Hey guys, have a g4+ with the plug in can connection, im currently running a Link AIM Dash (mxs) from this connection using a 1.5m cable from NZEFI.  
 

Im now wanting to install the link Lambda kit which runs over the can bus.  NZEFI have a duel device cable with one short tail amd one long tail, but im told you cant plug an extension into the short tail as this will mess up comms.   
 

This is a problem as my dash is a good 1m+ from the link ecu and the lambda sensor will also be 1.5m+ from the ecu. 
 

anyone had experience with can cable lengths to multiple devices?   
 

another option could be to buy or make an extension cable for the lambda sensor to the lambda can module, the sensor link uses is a bosh LSU 4.9 unit with An approx 300mm tail I believe.  
 

thoughts?

 

thanks

[Adamw]

The CAN bus itself can actually be very long, but the length restriction comes from the "stub length" or "spur length", which is quoted in many standards to be 300mm max. 

In your case you now have the ECU at one end of the bus and the dash at the other end so effectively if you connect the Lambda in between it will be considered a stub.  Something like below

However as a general comment the Link stuff seems to be fairly error tolerant and I think most of those standards are very conservative, I have never had any drama with longer stubs so Im pretty sure you would get away with the "double adapter" and a 1.0 or 1.5m stub as you planned.  I just cant guarantee it as I usually try to follow the rules so dont have enough experience at breaking the rules...  Having said that, many competing ECU brands now sell the "CAN hubs" which break most of the CAN rules but still seem to work.

What ECU do you have, does it have a 2nd CAN port?  Do you have any ability to do some basic custom wiring (like crimp tools to crimp a plug onto some wires) or have any contacts that can?  Where abouts are you in NZ?  I will make a suggestion on some other options based on the answers to these questions.

 

[Funkyflynz]

15 hours ago, Adamw said:

The CAN bus itself can actually be very long, but the length restriction comes from the "stub length" or "spur length", which is quoted in many standards to be 300mm max. 

In your case you now have the ECU at one end of the bus and the dash at the other end so effectively if you connect the Lambda in between it will be considered a stub.  Something like below

However as a general comment the Link stuff seems to be fairly error tolerant and I think most of those standards are very conservative, I have never had any drama with longer stubs so Im pretty sure you would get away with the "double adapter" and a 1.0 or 1.5m stub as you planned.  I just cant guarantee it as I usually try to follow the rules so dont have enough experience at breaking the rules...  Having said that, many competing ECU brands now sell the "CAN hubs" which break most of the CAN rules but still seem to work.

What ECU do you have, does it have a 2nd CAN port?  Do you have any ability to do some basic custom wiring (like crimp tools to crimp a plug onto some wires) or have any contacts that can?  Where abouts are you in NZ?  I will make a suggestion on some other options based on the answers to these questions.

 

Thanks mate.

What ECU do you have, does it have a 2nd CAN port? G4+ Extreme, only has a single external CAN port.

Do you have any ability to do some basic custom wiring (like crimp tools to crimp a plug onto some wires) or have any contacts that can? Yes no problem on this front.

Where abouts are you in NZ? Im based in New Plymouth.

 

Thanks

[Monsterbishi]

16 hours ago, Adamw said:

However as a general comment the Link stuff seems to be fairly error tolerant and I think most of those standards are very conservative, I have never had any drama with longer stubs so Im pretty sure you would get away with the "double adapter" and a 1.0 or 1.5m stub as you planned.  I just cant guarantee it as I usually try to follow the rules so dont have enough experience at breaking the rules... 

Canbus stubs can be quite a bit longer, most modern cars are a veritable spiders web of the things! 

[Adamw]

2 hours ago, Funkyflynz said:

G4+ Extreme, only has a single external CAN port.

Is it an old Red xtreme?  The Black Xtremes have two CAN ports, one is the round plug, CAN 2 is on the B connector.  

But if you want to keep it all on the same bus then my suggestion would be as follows...

Turn off the termination resitor in the dash software.   Splice 2 new CAN wires in to the connection at the dash, then run these to your CAN Lambda, it can be as long as you like since the Lambda is now the bus end rather than the dash.  You will need to add a termination resistor somewhere near the CAN lambda.  So effectively it will end up looking like this:

 

[Funkyflynz]

Hi Adam, its the old Red Xtreme model.

In the interests of keeping things neat and tidy i brought the NZEFI duel device cable.  Problem is whatever i plug into the short tail (Link AIM Dash or CAN Lambda) doesn't seem to want to talk to the ECU.  When either device is plugged into the long tail it seems to work.  Strange. 

[Adamw]

Beep it out with a multimeter, check CAN H is the same pin on all plugs and CAN L is the same pin on all.  There was someone on this forum a little while ago that got one of those that nzefi cables with one plug mis-pinned.

[Funkyflynz]

22 hours ago, Adamw said:

Beep it out with a multimeter, check CAN H is the same pin on all plugs and CAN L is the same pin on all.  There was someone on this forum a little while ago that got one of those that nzefi cables with one plug mis-pinned.

Nice one Adam, that's exactly what the issue was, the CAN Hi and Lo were terminated incorrectly on the short tail.  Called NZEFI and they said either send it back or switch the pins, I decided to switch the pins.  Now I have both the Lambda and Dash working, brilliant.  Now on to the next question..... LOL  Thanks Again for the reply on a Sunday night mate.