What's the OBC (On Board Computer) do? (the thing in some tachs)
 

Hi,

I'm getting the OBC (On Board Computer) to work in my 914 with a 1991 964 engine. Problem is, I've never actually used one or seen it work.

More install info here:
http://p-car.com/diy/obc/
(thanks Keith Burrell - this has been very helpful)

From what I can tell, it looks like it has 4 "actions" (on the stalk?):

- go to next function
- go to prev function
- reset current function
- setup (show all functions at once, one blinks) (or something?)

Is this right? Could someone walk me through how you use the OBC in a normal installation (I pull forward to do this)? What's the weird "setup" setting I found?

Next [harder] question: Does anyone know if the "Central indicator" is required for the fuel function to work (i.e. does it do any processing), or could I just connect the fuel level signal directly to the tach/OBC?

Thanks!
Steve

Really? Nobody knows... How rare of option was the OBC? I thought it came on all Turbos and Tiptronic cars, and then was an option for others... ?

-Steve

1) Distance to empty
2) Average miles per gallon
3) Average speed
4) Outside temperature
5) Tripmeter

I can't think of anymore that I've seen scroll by...

Thanks for the response...

So what are the four "actions" you can do?

#1 & #2: Scroll through the options (prev and next)

#3: reset

#4: ?

Thanks,
Steve

I don't believe there are four functions.

I only see the three you've outlined:

1) Scroll up
2) Scroll down
3) Reset

Ah ok, that answers my question! Thanks!

I guess whatever it is that my tach does (when I ground this mystery 4th wire it looks like it goes into setup mode or something) isn't needed. I'll actually probably only set it up with forward and reset (will be using the 914's limited switches).

Thanks again,
Steve

DON'T CUT THE WIRE!!!
 

I just went out to the car and actually CHECKED.

THERE IS A FOURTH FUNCTION!!!

If you push the stalk forward , the display changes so that the units of measure (distance to empty/average mpg/average mph/tripmeter miles/actual mph) are ALL SIMULTANEOUSLY illuminated along the bottom of the display.

By flipping the stalk up or down, you "scroll" through the various icons which FLASH when the associated numeric value is selected.

Notice in the features listed above that I neglected to tell you of the instantaneous (actual) mph feature in my prior post.

Sorry! Should've gone out to the car and checked it rather than relying on memory!