Part of Lesson Plan: **Ingredient 1: Fuel (updated) by Thomas Dougherty

Activity Overview / Details

At the beginning of the class I wander through the tables asking the students what they have in front of them.  Many of them can identify a carburetor, but when asked how it works, few of them can answer.  I ask them if it is physics or magic.  All of them can identify the water bottles and tubing but none of them recognize it as a carburetor. 

I fill one of the bottles with water, insert the tube and explain to them that I have just built a carburetor.  I explain that it has a fuel reservoir, an emulsion tube and a jet.  We then identify those parts on the different carburetors on their handouts as well as the idle circuit, main circuit and metering screws. 

When the pressure at the end of the tube is lowered, atmospheric pressure will push the fuel into the airstream. I explain that on an actual engine the pressure drop is caused by the vacuum created by the piston travelling down with the intake valve open (the intake stroke).  I then allow them to fill water bottles, insert tubes and blow compressed air across the end of the tube with a blowgun.  Students witness the water being sucked from the bottle and atomized in the air stream.  By varying the diameter of the tubing and the amount of air being blown across, it they will simulate jetting and fuel flow.