no, I am not trying to reinvent the wheel... the thing still is, once you've got some sort of data that you can feed into your Arduino/Atmega architecture, all you have to do is wire it up and dump about 300, maybe 400 lines (it sounds like a lot but it really isn't when you're in the midst of it) of C code onto the Atmega chip to have a full range of information put out on a display, like MPG, range, remaining fuel, and momentary consumption. Programming it will take a few weeks, but will not be difficult. Something to do over the coming winter.
And I am not the first person to have the idea of implementing something like it in a car; in fact,
this guy here did something very similar to what I am planning, except he salvaged a monochrome LCD display from an old Nokia phone, and I would use a not wildly expensive
high-resolution 1.5'' OLED colour display. I've got in touch with him, and he has offered to help with questions I might have.
His description is well worth a read, as is the C code he supplied at the bottom of it. He looked at injection cycle lengths using a Citroen-specific Testbook-like device, but his way of calculating fuel consumption was more "roundabout" if I understood correctly; he didn't use the signal from the ECU to the injectors directly (PSA Peugeot Citroen engine, but quite similar specs as our MG engines; 1.8-litre, 16V DOHC MPI, "grouped" injectors), but instead he worked out a linear correlation between engine RPM and injection time in milliseconds as measured with his "Citroen Testbook", and then, he used that RPM signal from the transmission (again, very similar sounding to the MGF) to calculate fuel consumption "indirectly".
Again, it's not witchcraft. It's "tap into a consumption signal or generate data correlating with it --> log that data/do calculations with it --> dump it out on a screen --> refresh every 1 to 5 seconds to your liking". Done.
And I've already found the relevant injector specs:
EDIT:
I've dug my way through the electrical library, and this is what I found:
This is where I'll get the data to feed my trip computer
![Thumbs Up :thumbsu:](./images/smilies/afro.gif)
. And because I will simply have to tap the wires right at the ECU module connector plugs, it means I will only have to run one single four- or five-wire DIY loom (depending on what other data I want to retrieve) from the back of the car to the front, where the control module for the trip computer will be located.
This is going to be a major project and I don't expect presentable results before next spring, but as it stands, I see no major insurmountable obstacles in its feasbilility.
One more question: I am thinking about investing in an entry-level oscilloscope (no more than 80-100 quid) to analyse the signals so I will know how to process them. Are digital USB oscilloscopes worth their money, which can be had from about £50, or should I buy a used stand-alone "hardware" oscilloscope??