Good question. Engine speed and load will have an impact on how much fuel in consumed at any throttle opening.
What basically happens is that the pressure differential above and below the throttle plates changes (engine vacuum). The differential in pressure with additional load simply pulls more fuel from the main boosters. This is the magic of the venture principal, and why carburetors work so well as metering devices.
Changing the throttle angle has the same effect at the same engine load. The quadrajet in particular has a very sensitive booster area due to the design of the center booster and outer rings. It has always been a very efficient carburetor, being very sensitive to engine load/speed changes.
The booster design and multiple areas provided by the rings and venture also do an excellent job of atomizing the incoming air/fuel mixture. Unlike Holley's, AFB's and other carburetors with a relative large primary bore area and small boosters, the Q-jet is much more efficient for light engine loads, which is where most applications spend most of their time.
The q-jet also makes an excellent Marine unit, with the jets on the bottom of the bowl, center hung float, and centrally located fuel bowl, they do well with "rough" conditions and relative steep angles.
Hope this helps some......Cliff
