Canbus?

[BamaRider]

Along with maturity comes the knowledge the only dumb quesiton is the one not asked, so in that vein, here I go.

 

Exactly what does the Canbus do, and what makes it better than previous applications? I know it has something to do with electrics, but not much else.

[steve.foote]

Actually, it has to do with electronics more than electrics.

 

The canbus system is essentially a power and communication system (for the bike) in one. Using two wires, it can communicate instructions and transmit power between a number of devices and controllers. Advantages are that it is electronically fused and weighs less than traditional wiring systems. And, because the "smart" devices are essentially computer controlled, they can be programmed.

 

Though the point is argueable, the electronic nature of it is supposed to make it more reliable.

 

On our bikes, though, the CANbus is all but invisible. it forms the core of the electrical/electronic system. Most of the wires you see going to lights and such are traditional wiring controlled by CANbus devices and are not actually CANbus devices themselves. This is why you can tap headlamp circuits and accessory wiring to trigger relays and power some devices without causing faults in the system.

[Zeiser]

The CAN (Controller Area Network) bus is the way found by car manufacturer and supplier to reduce the number of wires.

Designed at the beginning by Bosch, it is a 'serial communication link' to exchange information between several ECU.

Example : where comes the speed information displayed in the speedometer ?

. previously : a mechanical or electrical sensor is located in the front wheel and connected to the speedometer.

. CAN system and RT : as there is already a sensor in the front wheel (for ABS features), to be the most cost effective, the speedometer will use this sensor. How? -> the ABS ECU will send on the CAN bus the 'speed' information. Therefore, all others ECU connected to the CAN bus can use this information, without additional cost : The speedometer will use it, but also the radio (automatic volume adjustment depending of speed).

 

So, the manufacturer will be able to :

. reduce cost (less sensors, less wires (i.e less copper and weight))

. additional features for free (if the information is available on the CAN, the only thing to do is the right software). It will not add any product cost, but the manufacturer can raise the price (more features !)

Example : the on board computer (for the RT) is additional software in the instrument cluster and one additional button 'BC'. All the information displayed on the LCD is available on the CAN bus (even if you havaen't this option).If you have a look on the option price, you can imagine the margin made by BMW !!.

 

BUT ....

. additional features means .... additional softare which means... additional bugs ! The main problem for every manufacturer is now on this point : as the developement schedule is shorter and shorter, the software can not be tested completely.

Sometimes, the vehicle is on the market before being completely tested. It means customer insatisfaction. To give you an idea, Mercedes has decided to reduce features in the new class S car (to reduce bugs and customer claims !!).

 

 

Michel

[Mainuh]

This pretty much echoes what's already been said, but this is an excerpt from BMW's UK press release on the RT earlier this year for the UK:

 

"On-board network – CAN-bus technology

With fewer cables than ever, the new on-board network ensures a high standard of reliability plus an even wider range of functions. The single-wire system transmits all relevant data via one single wire to the respective control units.

 

Physically, it is a double-wire system with CAN-bus (Controller Area Network) technology consistently interconnecting all control units and the central vehicle electronics (CVE) to form a permanent data network – the various units exchanging data with each other. Apart from simplifying the main wiring harness it also allows efficient, comprehensive diagnosis of all vehicle functions.

A further advantage is that the system no longer requires conventional fuses. CAN-bus technology automatically switches off the suspect component – where possible – and checks whether the function is still defective when the rider again starts the motorcycle.

 

The network also serves to feed all data to the cockpit display on the info-flatscreen.To easily adapt and integrate electronic accessories into the on-board network, there is a plug for special equipment. The lightweight alternator supplying the power required by the motorcycle has an output of 720W at 60 amps. The 19 ampere-hour battery is maintenance-free. Electronic immobiliser fitted as standard BMW Motorrad’s electronic immobiliser is an integral part of the modern on-board network. Making life very difficult for the potential thief, this security system offers the best technology currently available to prevent unauthorised use of the machine. The authorised rider benefits from a high standard of convenience – all that is required is to pull the key out of the ignition; the immobiliser intervenes in the engine management software and deactivates fuel-injection and ignition.

When the rider next wishes to start the engine, a chip in the key compares its data with engine management data to determine compliance. Once the proper match has been established, the engine control unit switches on the ignition and the rider can start the engine."

 

I pick up my new 05 RT Saturday. I think every trip to the dealer now will involve plugging into their computer and reading the onboard computer on the bike (for a fee of course) to see how things are going. It also means you must be VERY CAREFUL when hooking up any electrics like driving lights etc. The dealer told me that the BMW accessory plug onboard is limited in how much wattage it will provide before shutting down. Some electric vests (I think they mentioned Gerbings) will be took much for it. The way around this is going direct to the battery. They did say I could hook up my motolights to the battery. I think a mini bus bar off the battery will probably be in order as I also want to electrify my tankbag and will run my vest or charge my cell phone off that rather than the onboard socket.

[Jim VonBaden]

...

I pick up my new 05 RT Saturday. I think every trip to the dealer now will involve plugging into their computer and reading the onboard computer on the bike (for a fee of course) to see how things are going. It also means you must be VERY CAREFUL when hooking up any electrics like driving lights etc. The dealer told me that the BMW accessory plug onboard is limited in how much wattage it will provide before shutting down. Some electric vests (I think they mentioned Gerbings) will be took much for it. The way around this is going direct to the battery. They did say I could hook up my motolights to the battery. I think a mini bus bar off the battery will probably be in order as I also want to electrify my tankbag and will run my vest or charge my cell phone off that rather than the onboard socket.

 

It is easy to install accessories, just do what I did.

 

The R1200GS Canbus system is somewhat reluctant to be messed with. OK, that is an understatement. It wont tolerate being messed with.

 

So, if you want to add accessories, you need to either wire them directly to the battery, or create a fuse box. Of course for the fuse box to work right, and to prevent your accessories from killing the fairly small battery on the 12GS, you need to hook the fuse box up to a relay.

 

Here is the wiring diagram I made up, and used. Note that I have the GPS wired directly to the battery still, since I want power at all times. If you have a unit with a battery, you can use the fuse box.

 

 

Lots of wires can be messy, but BMW was thinking about us when they elected to furnish a tool kit with no tools in it (for all intents and purposes), so I put the fuse box in the spote where the tools used to be. It is the perfect location.

 

I used a Blue Seas fuse box because it is a quality unit, and marine rated for protection, so I figured it would work on a bike. I got it for $20 on E-bay new.

 

 

The relays are under the fuse box, and it is held in place by the tool strap. This makes it easy to lift up if you want to add more accessories, or change a fuse.

 

 

The big picture. Pretty clean considering I did it in 25 degree temps, outside, at night. When I add more lights I will make the wires a little neater, but it works.

 

 

I took the signal power for the main 30amp relay, purchased at Pep Boys for $3.99, from the testing plug at the back of the fuse box. I used the green wire with blue stripes because it is ignition on only, so the fuse block is only powered when the key is on. The power needed is so low that the Canbus ignores it.

 

When I wired up the fuse box, I also installed some new Motolights that I got for a steal at just $250. They work well, though I may add more light, as you can never have too much.

 

 

The big picture.

 

 

The wires coming up the brake lines are nearly unnoticable.

 

 

I put the switch on the inside of the left brush guard, which lets me turn them on and off with my index finger, bit is out of the way.

 

 

Anyhow, it works great. I did 200 miles today and no problems. After dark the Motolights definitely improved on the already good stock lighting.

 

I also routed the power for my electrics to the fuse box, and have set it up to add my new FIAM horn as soon as I find a 5amp relay.

 

Next...

 

Jim

[Mainuh]

Hi Jim,

 

Thanks for the photos and the excellent info. I think I had seen another post of yours (or someones) earlier. I had already ordered 2 fuse blocks earlier this week (my best friend is also picking up a new RT with me tomorrow when I pick up mine!!!). So we'll have some fun accessorizing during the long Maine winter! Thanks again for the info!

[Survived-til-now]

Don,

 

A good reason for that trip to the dealer for a hook-up is that the computer on the R1200RT needs software updates from time to time. I had a flat battery problem one frosty night and learnt from this site that the CANBUS computer (black box to me) was susceptible to leaving itself on if you weren't careful. Later software issues have solved that or made it more difficult for the computer to be accidentally turned on/left on....

 

Also the fix I got this week sorted "a range of problems" but my friendly dealer didn't specify. But one of them was a fuelling improvement at lower revs - very nice.

 

Resign yourself to regular servicing and software updates!

 

regards

 

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