Port fuel injection, where the injector is located at the port, greatly reduces the problems of manifold design, relating to fuel distribution, separating, heat soak, and speed of the mixture traveling through the runners.
Because there is no fuel trying to go through the main portion of the manifold, the mixture is less dense, and will travel at a greater velocity. This higher velocity means more air should enter the cylinder. If greater amounts of air can fill the cylinder, combined with the proper amount of fuel, the engine should produce more power and better economy.
Care should be taken in the design of the system components with factors of R.P.M., C.F.M., and horsepower being main considerations.
The cubic feet per minute that an engine can consume will determine the size of the throttle valve, and the manifold style and design.
R.P.M. and horsepower levels play a big part in the sizing of the injectors. Obviously too small an injector will starve an engine, if not do serious and irreparable harm.
It should be remembered that maximum fuel consumption occurs at peak torque. However the injector capacity needs to be bigger as the R.P.M. increases because there is less time available to inject the fuel.