Theoritical intake velocity
 

It is cold outside, even in the South, so I am stuck inside pondering.

A carburetor engine needs intake velocity to achieve the venturi effect and draw in fuel. What about a fuel injected motor where the fuel is sprayed in under pressure, does it need intake velocity and why? Can a gasoline engine run without butterflies like a diesel does, modulating the throttle with the fuel delivery?

Just a few things swirling around in my head. any opinions?

Gas and diesel are two different combustion processes. Gasoline requires a semi stochimetric mix and thus fuel and air need to be metered since it burns from the spark ignition point.

Diesel is combustion 'all at once' since it starts burning as soon as it is injected. Well, close... there is a delay period before the fuel lights and this is what a larger cetane number gives you (more delay).

One could say that diesels and gasoline motors require the direct opposite out of their fuels.

This was a GREAT read:
Internal Combustion Engine in Theory and Practice: Vol. 2 - 2nd Edition, Revised: Combustion, Fuels, Materials, Design [Paperback]
Charles Fayette Taylor (Author)

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Diesel engines are direct injection. They do not need throttles as the mixture controls the power and speed. Modern gasoline direct injection systems can run on similarly widely varying mixtures, provided the temperatures do not get hot enough to cause damage. Direct injection engines could conceivably run like a diesel with no throttle. The BMW Valvetronic engines already do this, using variable intake and exhaust valve timing AND lift to function as the throttle.