[oldbeaver]

Dear TheTestPilot,

Clever idea of yours! I think this should work. Sure will need some electronics to convert pressure properly to a variable that represents volume injected.

Thinking loud on the same idea, we can count the injection pulses per minute, just counting the rpm pulses, right? Injection pulses per cylinder should be rpm/2 in a 4 stroke engine. As my engine has 6 cylinders, number of total strokes are 3 per revolution of the engine.

Based on the injection pump data, I can know an approximate figure of injection volume per stroke either. Further on, I can make a family of convex curves that represent the volume injected per stroke as a function of rpm. This function is a parabola (quadratic) function.

So total volume is K*rpm^3 (approximately).

What I don't know is how does throttle position determine to the amount of fuel injected on each stroke. There are models for that.

But this is just an approximation to the real injected volume.

Your approach, allow us to have a measure of real volume injected, whatever the surrounding conditions. I like it very much.

We need a pressure sensor that gives a continuous measure of pressure, so we can generate a continuous flow value as well. Definition of minimum and maximum pressure (this has a name I cannot recall now) to determine pulse duration is crucial too. Having pulse duration and pulse flow (stroke duration and stroke flow) will get a very good approximation to real volume. Then comes callibration.

Maybe we can make:

Volume per stroke = Stroke duration x mean pressure

Volume per stroke = Stroke duration x (Max pressure - Min pressure)/2

Futher we must count the number of stroke per unit of time, to get:

Volume/hour = volume per stroke x number of strokes/hour

I don´t know what kind of signal is MPGuino expecting, but this kind of signal should suit.

My problem is to build an extra circuit to make all the necessary processing previous to input the signal to MPGuino.

Therefore, in your approach the pressure sensor is key.

This is my comment. Looking forward to yours.

Oldbeaver