The task is to measure in real time, diesel fuel consumption in a MB car with a 6 in line diesel engine, 2.8 liters, aspirated, non electronic.
Well, despite the many difficulties, I succeeded in creating a reasonable math model for estimating diesel fuel consumption over time, as a function of rpm. This model was developed based on the tech sheet of the Bosch injection pump in the car.
I adjusted a parabolic curve to data of the fuel consumption at several rpm of the Zexel diesel pump, obtained by Bosch at their lab, considering full load, which I assumed is full throttle.
A second step was to sense throttle position, as a ratio of full capacity, to modulate the consumption curve.
The third step consists in dividing speed in km/ by fuel in lt/min to get performance in km/lt.
I have all these programmed into an Arduino sketch and results are reasonable. At least, if I complete the project, I will have good reletive measuring of the yield of the car, in real time. The need of that is for being able to test several fuel saving devices in real time.
Sensing throttle position was no problem. However, I haven´t succeed in getting speed and rpm signals into Arduino so far. Arduino do not recognize them so far.
As I haven´t a signal generator, I cannot realize where is the problem. If If I had input a secure test signal, I would have gotten quicker results.
The routine program for rpm cannot be tested also, as I do not have a trustable input signal.
This is update Nr 1 to my work.
Thanks to the forum members that has helped me, specially mem but others also.