This is great! A quick search of my car's manual and I've found the pins for VSS and the injectors on the ECU, so it shouldn't be too hard to hook up.
A question, though. Is it possible to customise what data is displayed? I would only need, say, instant L/100km and L/100km-since-reset (per tank, really). Would it be possible to set it up so that only these two figures are displayed on startup? If I could tap into the reset button on the trip meter it would be good, too. Only one button to push, then!
Secondly, is it possible to rig it to adjust the backlight brightness to match the instrument brightness? That way I wouldn't have a bright light in the middle of the dash at night. I could always set it to a decent night time brightness and let it shine on during the day, but it would look more professional if the backlight came on and adjusted with the same control as the rest of the cluster.
Ideally I'd buy a 3 or 4 x 2 character LCD and stick it between the speedo and tacho on my dash, so it looks like Subaru put it there. But I haven't really seen anything other than 16x2 out there.
I'd rather it wasn't taped to the dash with wires running everywhere.
I'm still not 100% on exactly how this works, but I like the idea, and it'll be a good project until I start my EV conversion. (Speaking of which, could this be reworked to provide Wh/km data?)