To: CRAN
In a conventionally aspirated engine (with a carburetor) the fuel air mixture passes into the induction system. This mixture must change flow direction in order to pass through the headers leading to the individual cylinders. During this change in direction you get a condition called “Centrifugal slinging” which causes some of the fuel to separate from the airflow. This separated fuel will end up in the cylinder(s) closest to the carburetor and the difference in fuel air charge will cause the closest cylinder(s) to run rich and the furthest cylinders will run lean. This difference will cause a difference in the exhaust note for the various cylinders and possibly result in a harmonic amplification of the noise emitted by the exhaust.
Fuel injection solves this problem by injecting the same amount of fuel directly at the intake valve.
As far as icing is concerned it should not happen even though there is a butterfly valve. Icing is caused by the expansion of the fuel air mixture as it comes out of the jet and passes through the carburetor. Any time you have expansion you have cooling which cools the carburetor body. Flying through moisture laden air at a specified temperature assists in this cooling and the moisture accretes out on the carburetor body, building up to the point of causing engine stoppage.
This should not happen on an injected engine.
Many moons ago the Holly Carburetor company designed a carburetor that would not Ice-up. The US Navy had some problems on the carbs. on R-2800 engines. They installed this carburetor on many R-2800s used on PBMs. They lost several PBM due to engine failure (both engines at the same time) because the Holly anti icing carburetor generated ice faster than an ice machine in a restaurant.
