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Discussion Starter · #1 ·
I'm interested in making an MPGuino to help improve fuel economy in my 2008 LX. Could you guys help me locate the VSS lead and fuel injector lead? Also, do you think there would be an easy way to get a connection that is not permanent (e.g., no stripping/cutting)? Thanks so much folks!
 

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Discussion Starter · #3 ·
Do you think there's a way to tap into that without stripping/cutting? Maybe a thin wire inserted into the harness or something?

Any idea on the injector lead? I am not sure because I don't have like the technical manual or anything...is there an online source of these sorts of diagrams for free?
 

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You can just use one of those (T-taps?) You clamp it to the wire and then it allows you to plug in a connector without having to cut or strip. Radio shack would have it.

As for the injector lead, you may want to ask around in the forced induction section. They problably have more knowledge about tinkering with the injectors and such. I don't know what kind of signal the arduino is going to look for to do the calculation. I guess taping into one of the injector wires would be enough because I would think they would all be receiving the same signal for the same amount of fuel so that signal can be deciphered and multiplied by 4.

I just thought of this. There is probably a some kind of injector signal at the obd2 port which is right behind the plastic cover under the steering wheel by your right knee. The Scangauge does all these functions of this MPGuino and more by only plugging into the obd2 port. Maybe you can get a pinout for the obd2 port somewhere.

My other thought would be off of the ecu somewhere. Again, maybe the forced induction guys would know.

Good luck. Looks like a fun project. I might attempt it but I got my scanguage already.
 

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Discussion Starter · #5 ·
Well they were designing that MPGuino to not require OBD-II, but I don't care about that because I have that--my only roadblock to getting a ScanGaugeII is the triple-digit price, to be honest.

You know I have been thinking about this for a while now, and I bet there is a way to make a sort of ScanGauge "lite" using a simple microcontroller setup or maybe something based on arduino to just get instantaneous and trip MPG. VSS is easy to get via OBD-II (it's just Mode $01 PID 0D, given in straight km/h). But there is no spec in OBD-II for fuel usage!

Does anyone know what parameters are used by the ECU to determine how much fuel to inject (these parameters such as engine load, engine rpm, throttle position, etc. are retrievable via OBD-II), in what way? If we could figure out some factor of current fuel economy, it would be easy enough to calibrate (as is needed in ScanGaugeII and MPGuino alike).

You directed me to forced induction for the injector lead question...is there a better place for this? It isn't exactly mechanical....
 
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