Originally Posted by
cmulder
would that pump surfive pumping fuel ? then you would have a much more direct flow controll compaired to compressing a gas.
power it trough a small brushed esc for example.
Won't work... the difference in volumetric efficiency is WAY too large.
Years ago, I experimented with direct volumetric metering. I used an old window-washer pump (one with a rubber impeller, pretty much leak-free and fairly precise) and I used an old servomechanics as drive. That ittybitty tiny pump had to turn so unvelievably slow, it was a total PITA to control the fuel flow. It was unstable as heck, since a leaning out of the engine would cause a rise in RPM, which would in turn increase the air intake volume, but the fuel flow remained the same. Resulting in further leaning out.
There is no stability in such a system, it has to be actively stabilized. Which means control-loops with Proportional, integral and derivative action...
Here I was still controlling by hand: