Hi,

I'm after some advice on dashboard instruments/gauges. I'm fitting a 2.8 BMW engine to my Viento and I've just started to do the wiring. I have the original BMW wiring harness and ECU and I assume that I need to tap into it somewhere to run the gauges.

I'm guessing that unless I want to use the BMW dash (which I don't), I will not be picking up the signals generated by the ECU, so this will be something like

i) speedo - pick up from prop shaft, therefore nothing to do with BMW wiring

ii) Revs - I have heard that this can be picked up from the HV coil. BMW's have individual coil packs on each plug, so not sure how to do it in this case

iii) oil/water. Do I just tap into the existing wiring loom somewhere between the senors and the BMW ECU?

Also, I cannot find anything in my manual or on line that describes what the voltage range coming from the BMW sensors are, so my other concern is whether the standard gauges will have the right signal range.

As usual, wise words from the members of this forum would be a great help, including pointing me at a good supplier.

regards
Steve

Personally I would have all the guages stand alone and not through the ECU.

As you say the speedo from a pick up on the prop.

I would have a separate water temperature sensor inserted into a sensor adaptor (see ebay) in the water pipe from the back of the head.

The tachometer can sometimes be from the ecu but you can also do the below with a diode connected to each of the 4 coils you have -so it would be 4 into one so to speak.




[img]
tachometer diodes [/img]

[Edited on 23/10/11 by big-vee-twin]

Steve,

On my Ford the setup was:

Tacho - an existing output from the ECU, just tapped in.
Speed - sensor off the front wheel hub (couldn't get the prop to work).
Oil - No oil temp or pressure on the Granny just low oil pressure switch which was fed from the sensor back to the dash warning light (i.e. not through the ECU which uses water temp as the guide to engine temp) - I replaced this single sensor with an offtake that allowed me to fit low oil pressure (to warning light on dash), oil pressure sensor and oil temp sensor (oil temp sensor is near the block, two pressure sensors slightly remote)
Water - Fitted a new water temp sensor nearer the rad in the top hose (i.e. doesn't read the block temp until the thermostat opens which I guess gives me comfort that it is!)

Some pictures in archive showing this - nearside front of block at bottom...

HTH, N.

If you are using a BMW diff there should be a speed sensor fitted into the back of it already.

Dan