I've got a question for the tech heads amongst us!

[Lt Ketch]

My question relates to the dash display on my JSII, I don’t have any other real experience to other Opel based cars so don’t know how relevant this will be to others!

I want to try and measure what is being transmitted from the Simtec ECU to the MID. From what I can tell searching for the limited information on the internet(and I could be very wrong), there is a single wire that transmits the instant fuel usage to the MID, from there the extrapolations for average fuel etc are calculated at the MID using this input and other inputs that do not come from the ECU, eg speed, fuel tank level.

Can anyone suggest how I could tap into this data/wire without destroying the ECU?

[InsaneAsylum]

do you know which wire it is?

if so you can partially strip the wire and connect the red terminal of a multimeter to the wire and the black terminal to the car body or a negative somewhere. that should work.

a few years ago, I built a harness to intercept the signal of my air flow meter. it basically had a few male and femal spades joined by wires. on intercepted the positive signal and the other did the negative. i set my multimeter to V and i coule see at idle i was getting 0.8V... as the load increased so did the voltage. it got up to 4.6V when it hit the limiter. it didn't damaget he ecu in any way.

[Lt Ketch]

ok will give that a go! it will be interesting to see what i get!

[InsaneAsylum]

just a disclaimer though, i'm not resposible if you fry your ecu. :)

has to be said :)

[Clint]

not sure if that will work in this case, i think the signal is in pulses, not 100% sure on that, but i can tell you a signal is sent to the MID which says when and how long the injectors are open for, by the time they are open it can calculate the amount of fuel going through per time period, from that working out the instant consumption. but this is only an approximation, as you can see by the formula, it isnt acurate, it works it out my the time the injectors are open, and from that calculates an approximate amount of fuel going through, it doesnt actually get a signal of the amount of fuel.

funny when you completely disconnect the fuel line and pump injector cleaner directly into the injectors it still says the same instant comsumption when it should be reading 0 cause there is no fuel going through!

if you want i can give you the exact wire you need, a while back i did a lot of research on the MID for the vectra/astra/barina, im working on getting my own text to write on the radio line of the screen

[Clint]

oh yea and may i ask what your intentions are... i am very interested :) and may be able to help

[Lt Ketch]

Thanks to both of you for the input it is very much appreciated! Where my thoughts are headed with this Clint you can blame on InsaneAsylum and a comment/thought that was put at the end of an answer that was given to a question I had asked not to long ago! It got me thinking “but what if….”

From what you say Clint, the data would seem to be duty cycle based! I have an automotive multimeter that has the ability to show duty cycle, I might try and tap into this connection and see what results I get! I have found at least one website where duty cycle (I believe tapped directly from the injector pulse) has been used to calculate instant fuel used then display it on an Astra display in place of the radio station or date.

See http://www.eelkevisser.nl/rado.html

If a stripped down version of this (or some other electronic gizmo) can be created to transmit the fuel data only in a form the MID likes, then the full functionality of the trip computer should then have no direct reliance on the ECU!

Then (and this is where it becomes what if and I wish based on my opening statement above) you could start to think about the possiblilty of using other ECU’s yet have all the fancy bits work properly, the buttons and trip computer are something I like about my car! There is nothing more I would like to do than take to Mr Simtec with an axe! :) As we all know performance parts for our cars aren’t exactly thick on the ground here in Oz! Let alone whole turbo engines of a suitable age that would still let my JSII remain ADR compliant……ie Legal! Yet it doesn’t take much effort to see that some importers of performance motors from a certain northern pacific country are around with abundant supplies at quite reasonable prices! I then have to ask WHAT IF inside the car everything works as it always has BUT when I put my foot down I get a shove in the back from a Turbocharged Japanese Demon????? Oh and if anyone needs to know NO I do not want or intend to sell what I have and buy a Japanese car that already has these parts, what would the originality be in that!

These only thoughts at the moment but I find them happy thoughts!

[Clint]

seems that is one of the only sites on the net with info about this haha, i have also come across that one and got some useful information from it.

yes i believe it is duty cycle based

[Lt Ketch]

seems that is one of the only sites on the net with info about this haha, i have also come across that one and got some useful information from it.

At least in english anyway, I have a suspicion that on some of the german forums similiar topics may have been discussed but seeing as I cannot read German (some would say I have trouble with English as well :) ) it makes it a little hard to do searches!

[Clint]

yea there was a few topics on forums in german, not much help to me lol

[Lt Ketch]

Today I made a patch into what I think is the Fuel Signal wire coming from the ECU to the MID.

654

Connected my multimeter ....AND...well nothing really happened... on the voltage setting I got some strange pulsing and that was it! Not a total loss though I can say that the fuel signal is more than a simple duty cycle as that setting on my multimeter did not recognise anything, but I expected that anyway!

So now that I have this wire coming fom my ECU does anyone have a suggestion on how I can start to explore what form the data being transmitted is? Is their any way I can connect my computer up to this thing to record it?