Will OBC still work with stand-alone engine management?

[Giddyup58]

Hi all. I have just purchased an Australian E30 325is (which I haven't actually seen yet...oh dear...) and to my horror, I have discovered that it was never optioned with a very desirable, and I would have thought, necessary, option - an OBC.
I have read the Wiki on retrofitting an OBC and it all seems to make sense.
My question is, How does it work?
From where does it pull the raw data for fuel consumption, distance to empty etc? Is it totally independent of the engine management system, as I intend fitting a stand alone computer to run fuel and spark.
Also, the "econometer" that lives under/in the tacho, and the Service Indicators - same story? Will they still function if I fit stand alone engine management? Many thanks...

[staley_turbo]

I have stand-alone fitted, My econometer doesn't work anymore as that takes the signal from the original ecu. The OBC then takes the data from the clocks so the mpg on the obc also will not work. I am looking at ways to wire this up though. Everything else should stay the same. I had complete engine loom made, and rewired into the original plug. So all my gauges work.

As far as i can tell the econometer only takes a few signals, like rpm, speed, tps etc so this may be quite easy to reinstate.

[Giddyup58]

If you ever figure it out, please keep me in the loop. I'm quite keen to have all the instruments functional.
I don't have a choice with the stand alone, as the factory computer can't run my engine - 2.7 stroker, 323 head, 325 valves and intake manif, headers, schrick 288, 3.5 TB etc....

Would keeping the factory computer aboard but disconnecting it from the fuel injection and ignition circuits work? I'm thinking it could then collect and process the raw data, thus enabling the OBC and econometer, but not interfere with the actual running of the engine.

Could it be that simple? Would it be it simple to do?

[staley_turbo]

I will. Im not sure how far the standard ecu can go in regards to n/a tuning but I know its not much use with f/I like in my case.
Keeping it in there will only work if your using a piggy back type aftermarket ecu, not stand alone as you can only take one signal per sensor.

[Giddyup58]

Drat! I'm actually an electrical fool. I had no idea about one signal per sensor. I would imagine it'd be quite difficult to set up duplicate sensors. TPS jumps to mind - can't think how to do it....
Can't go piggy-back, as already have the motor tuned to the stand alone, at hideous cost.
But I really want the OBC...

[staley_turbo]

What management are you using? Yes, im also quickly racking up a huge mapping bill.
You can still install and use the OBC. You just wont have the mpg. This is what im doing for now.

[Giddyup58]

Hi. I'm in Australia, and the engine has a MoTeC computer. Don't know if you've heard of it over there, but here, all the pro racing guys use MoTeC. It's supposed to be a big deal, with data logging, boost control and a dozen other things I have no use for. The actual tune wasn't too bad, it was the cost of making a custom engine loom and adapting the old school BMW to carry enough of the correct sensors to operate the computer properly. Mine has crank angle sensor but still has a distributor. No cap or leads, but it's there with a sensor of some sort, (for what purpose I can not even guess) and that alone cost a packet to fabricate. But they tell me it is a lot better than a Mega Squirt, so I got it.
I can't think of anything, but what can the OBC do without mpg, apart from give outside temp?

[staley_turbo]

I haven't heard of it but it sounds good and will look into it. Im using Omex 710 that sounds about the same as what your using. Worlds apart from MS. Sounds like its the other way round for me though, custom loom and fitting was half the price of the mapping!
The OBC doesn't do much tbh, it is 25 years old now though! Im hoping to use the temp sensor to read air intake temp in my plenum ( after the intercooler )
But other than that its just a nice factory option that i wouldn't mind in my car.

[daimlerman]

OBC functions that I use in the order of usefullness;

Time/date
Average fuel consumption
Outside temp
Remaining fuel range

As I understand the OBC/service indicator/consumption swingometer,they all work together,gathering information from the various sensors connected to the engine ECU,so changing the ECU for a different unit will compromise the data collection,rendering the service indicator/swingometer redundant and limiting the OBC to a digital clock with an outside temp facility.

If you are clever enough,the swingometer and the sevice indicator could always be adapted to serve a more useful function,often thought that oil pressure temp would be of more use than fuel consumption!

[staley_turbo]

As far as I understood it, the service indicator has nothing to do with the ECU or OBC. The ONLY thing you will lose is mpg, but you lose the swingometer anyway when installing stand alone.

[cecotto479]

I'm not even sure that you'll lose mpg.

Is the mpg not calculated using injector timing data and distance travelled?

If it has the correct coding plug - I think it should work.

[staley_turbo]

If it does use that info, injector timing is missing. Mine does still move from time to time when it stalls or misses, meaning engine rpm is used.

[Brianmoooore]

SI indicator uses road speed data from the speedo (distance travelled), engine speed data (revs) from the ECU, and water temperature data, probably from the 'blue' sensor.
Econometer uses data from the fuel rate signal from the ECU, road speed data from the speedo, and throttle position from the TPS.
If the econometer works properly, then so should an OBC.

[staley_turbo]

Thanks for clearing that up, I new it didn't have many inputs. This shouldn't be to hard to wire up.

[Giddyup58]

Just to complicate the issue, here's another question.

No OBC's available in Australia. It's a numbers game.
No complete OBC's available in the UK (atm);
Several complete OBC's available in the USA.

Australian capacity works in metric (liters), UK in imperial (gallons etc), and the Americans don't use either - (US Gallons! WTF!).
I can think in imperial gallons and MPG, but not US gallons.

The question:

Can a US obc be reset to work in either imperial gallons or liters?

I have great faith that someone here will be able to solve the aftermarket engine management/OBC compatibility problem.

[daimlerman]

UK market OBC's talk three languages.

Euro(litres)
English(m/g)
American(mpg)

I cannot imagine that USA spec cars use a different unit from Euro spec cars.

[Brianmoooore]

OBC has three different settings got the three different markets, which are toggled through by pressing a couple of buttons on the front.
The only difference that there might be is the writing on the front panel.

[Giddyup58]

Thanks for that.

[e21Jason]

You can buy an off the shelf kit to drive the OBC with standalone. some thing like seattle digitial is the compnay name

Jason

[Giddyup58]

Thanks for that Jason.
I've just spent quite some time trying to find Seattle Digital or something similar that plays with BMW electronics, but I've come up empty.
Has anyone else ever heard of this crowd, and if so, who and where are they?

[staley_turbo]

I had a quick look yesterday and found nothing.

[e21Jason]

try here

http://www.seattlecircuit.com/

[Giddyup58]

Thanks again Jason. Sent him a message - I'll let you all know if he can help.