Wondering if anyone can help me understand these concepts to do with carburettor operation.
1/ How is it that float type carburettors meter fuel by volume and not mass.
Here is my understanding I'm wondering if I'm on the right track. The float type carburettor meters fuel at a certain rate depending on the static pressure differential between the float chamber and the venturi. Therefore the faster the flow through the venturi the greater the drop in static pressure = greater differential = greater fuel flow. This is unaffected by altitude as the reduction in density has the same effect on the static pressure in the venturi and in the float chamber thus the same static pressure differential is maintained.
2/ Why is it that increasing volumetric efficiency reduces Brake Specific Fuel Consumption.
I can't see how less fuel/air mixture being drawn into the cylinders effects fuel consumption as that fuel that is not used is still there to be used on the next intake stroke. The only thing that I can think is that the engine has to pull harder against a closed throttle meaning extra work has to be done ie. more fuel required for the same power output. I'm really struggling with this concept so any help is appreciated
Cheers
J