enginehistory.org

[dstauffer]

I know there are two kinds of carburetors referred to as "pressure carburetors". However, I am talking about the kind on normally aspired engines, not supercharged. These carbs use some source of pressure other than that between the venturi pressure and the float chamber pressure.

How are these pressure carburetors different than throttle body fuel injection?

[jschauer]

They use what is called impact air verses venturi to modulate the internal diaphrams of the carb. Impact air is sensed just ahead of the venturi and is a straight shot to one chamber, the venturi pressure is vented to the opposite side of that diaphram. The difference between the two causes the neeedle valve to modulate the flow of fuel to what I call the fuel spray bar downstream of the venturi. This is a real simple explanation, I'm sure someone can explain it better.

[dstauffer]

But isn't that essentially what the mass airflow sensor (especially the "paddle" type does in EFI?



"They use what is called impact air verses venturi to modulate the internal diaphrams of the carb. Impact air is sensed just ahead of the venturi and is a straight shot to one chamber, the venturi pressure is vented to the opposite side of that diaphram. "

[jschauer]

I'm not too familiar with EFI (I still own carbureted vehicles), but what the pressure carb does mechanically, the EFI (throttle body injection) does with computors.