Has anyone tried to retro-fit the 13 button 'big' on board computer (OBC) in place of the standard OBC?

 My car's got the standard computer and I'm thinking of upgrading. I've seen details of an installation where there was no computer at all to start off but what's involved to upgrade an existing computer? Is there a different loom for the two computers for instance? Can the computer itself just be simply swapped over?

Is the computer M3 specific or will any one do from an E30 without modification?

An ideas or experience appreciated.

Hiya mate see here http://www.e30zone.co.uk/technobc.asp - http://www.e30zone.co.uk/technobc.asp  for a great installation guide.

Basically you will need the unit, the wiring loom, gong, temp sensor, indicator switch and the control unit.

Fitting it is relatively simple, the wiring loom is plug and play into the exsisting junction box to get power, the control unit mounts on top of the ECU (well it does in a RHD car, not sure about LHD?).

Hardest part of the job was running the wiring through the bulkhead.

Bear in mind also that the wiring loom will be different between a LHD car and RHD car so try and get one from the states or lookout for an M3 breaking. Also all the 13 button units are the same, but for changing between engine sizes there's a coding plug fitted to the back of the unit which you will have to get if the unit is not from a M3, for more accurate (not that their accurate anyway) reading.

Thanks Simon. I'd read that helpful installation guide on the E30 Zone.

I presume from your reply you'd reckon the looms between the standard and 'big' computer would be different.

I must confess I hadn't even thought about the looms being different for LHD so thank you for that.

I'm beginning to think it might be more trouble than its worth.

Yes mate, the looms will be different as there's a remote function on the indicator switch, the 13 button has it's own control unit, where as the 6 button doesn't, the 6 button ony needs power and a wiring for the temp sensor. The 13 button one has a few more functions.

My opinion would be to go and scout you local breakers, get the OBC unit itself, the control unit, (will be mounted above the ECU) the indicator stalk, the gong (mounted in the cover above your knees) and the temp sensor, out of any E30, and buy a new wiring loom from the dealer, this should cost about £30-40. I regulary scout the breakers and remove anything that's of value to sell on e-bay, and a full kit will normally fetch around £120, but is costing me £30 from a breakers and about an hour to remove, would be a lot quicker to remove the above bits without the wiring loom, as this is the hardest part to remove.

I just remembered Ian Godney had an OBC in the M3 he was breaking, (I had the leather interior out of it) could be worth asking if he still has it.