Hello there,
Very nice project you have there! I have a special interest in this project because... I've been working a similar project with a friend in the past few months. This thread already very long and I don't have the time now to go thoroughly all of the posts, but would like to make some comments and show what I have.
I would like to start by doing 2 comments:
1) The power feeding on your circuit should have some protection against voltage transients, and at least a fuse. Voltage transients are quite common in cars and may end-up killing, instantly or by a slow degrade then death, your arduino. Sometimes, it's enough to turn off the air conditioned to cause a good transient.
2) The amount of fuel that goes into the cylinder is not proportional only to injector opening time. At least in some fuel injected cars (I don't have the knowledge to speak for all), the fuel pressure on the "injector rail" depends on the trottle position; there's a regulating valve which will regulate the pressure depending on the pressure at the air input (controlled by the trottle). In our project we're planning to take both things into consideration.
The stage I'm currently at is that I've built the core of the prototype hardware (based on a ATmega88) and I'm coding the basic software to read the sensors. Since I was going to pull some wires on the car anyways, I decided to bring more signals into the device, and add it more features, like displaying 2 air temperature sensors, a clock (the LCD will replace the current car clock), lambda sensor, extra kms (miles) counters, speed warnings and other things I'm still thinking about. It will be able to connect to a PC through a serial port and log data. Below you can see the schematics and a pic of the current prototype (still just a board, but it's heart already beats
). It's not the most updated schematics but that's the one I currently have on imageshack, I'll try to load a new one later.
Keep up with the good work, I hope we can exchange some knowledge.
Cheers!
