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Reverse Engineering a Daihatsu Mira ECU

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Helloween

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Hi,

I am in the process of designing an instantaneous fuel economy meter for my car. It will also have several other functions. I've figured out that I need the following signals:
-throttle position sensor (TPS)
-tachometer (RPM)
-injector (INJ)
-vehicle speed sensor (VSS)

Those are the main ones, although I might also like to be able to get coolant temperature or fuel guage.

I am detailing my progress on another forum here, but I figured this might be a better place to try and get some help.

Anyway, so far I have the VSS. The signal is like so:
**broken link removed**

The step goes to 4V. I will need to count this, because it steps every so many meters. I will need to count this via a microcontroller in order to get speed and distance.

And according to the pin labels on the ECU, this is IG, I assume "IGnition". It seems to correspond to the RPM. Here is what the signal looks like:
**broken link removed**
Note the 12 V part is 30ms at idle and the 0V part is 10ms at idle. Which is what, 25Hz? (It's a 3 cylinder engine.)

When the engine revs higher, the frequency of the pulses gets higher, and they all seem to cram together, however. But especially the 12V part, it becomes roughly equal to the 0V part.

Now, I know it's probably a stupid question, but what exactly would I be measuring? The most I've monkeyed around with cars is to change the oil, really. I figure that there is the information for RPM there. Is there anything else there of any note?

Thanks in advance.
 
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