I am a little confused (again). Fuel delivery and MAP are not directly proportional. The ECU takes many other parameters into account before deciding on injector timing etc, not the least of which is ambient air temperature and the charge temperature.
It does, my car is supercharged and I had it tuned with a speed density tune which uses manifold pressure from map to configure the tune. So the amount of fuel the injectors supply is dependent on pressure, rpm, temp. Etc. Instead of using a maf sensor. So your right about that.
However, this isn't what I was referring to earlier and I can see why your confused.
To create a more simpler overall picture I'll just explain the purpose.
My car is pretty heavily modified at this point, I use a large external fuel pump to supply fuel, however, running this pump at 100% all the time especially when your just cruising causes the pump to get really hot from recirculating the same fuel over and over. It also gets very loud as it gets hot.
To solve this I used a nano which sends a input to a motor driver that controls the speed of the fuel pump. The nano uses the map as a reference to control the speed. The map pressure changes based on throttle position. So at no throttle, just cruising pump runs at 30% at wot pump runs at 100%.
I would imagine there to be some noise/variance that causes the nano map input to sometimes differ from the nano fuel pump speed outlet. I want to make improvements to reduce possible variances and ideally if realistically possible, have a simple way to measure both these outputs from a device with a seperate power supply so the exact differences between the outputs can be taken into consideration.
The only way possible way I could think of doing this based on my noob brain, is taking another arduino board, powering it through my phone with an arduino app open to read serial monitor. Plug the one analog read pins into each output and of course connect the ground together between circuits because a common ground is always needed between circuits. In theory, since the 2nd board is not suffering from the same voltage variances as map and board, it should measure exact variances between the 2. However, I'm a noob and therefore is is a theory by a noob, so yeah. Looking for opinions and advice.