Fuel meter

A fuel meter, also known as a propane meter is used to inject a predetermined amout of fuel gas (usually propane) into the chamber of a combustion or hybrid. It typically consists of an adjustable pressure regulator and pressure gauge, connected to two ball valves with a length of pipe in between. The volume of this pipe and the pressure of the gas determines the amount of gas injected. The second ball valve is connected to the chamber of the gun. A fuel meter is operated as follows:

• The regulator is set to a predetermined pressure for the particular meter and chamber size
• The ball valve closest to the regulator is opened, filling the pipe up until the second ball valve with gas at the regulated pressure
• The first ball valve is closed again, closing off the section of pipe between the two valves
• The second ball valve is opened, the pressurized gas inside the meter expands and enters the main chamber
• The second ball valve is closed, and the cannon is ready to fire

The regulator usually only needs to be set the first time, and further fueling can be done simply by opening and closing the two ball valves. A fuel meter provides fast and very consistent fueling, and is the easiest way to use bottled gas for fuel.

Constructing a fuel meter and determining the correct pressure to use requires a few calculations. The Fuel Tool (found on Burnt Latke's performance calculators page) automates the fuel meter calculations.