How does an LPG fuel system work in a car?

by | May 12, 2009 08:00 AM ET

You Asked:

How does an LPG fuel system work in a car? --- Brian, Penrith, Australia

Marshall Answered:

LPG, or Liquefied Petroleum Gas, is basically propane (C3H8) and butane (C4H10). Gasoline has longer chains (like C8H18), so it is a liquid rather than a gas at room temperature, but you can see that both LPG and gasoline are nothing but carbon and hydrogen formed into chains.

To use LPG to fuel a car, you simply have to deal with the fact that LPG is a liquefied gas rather than a liquid like gasoline. The "gas tank" is going to be different (the tank in an LPG car needs to be able to handle a pressurized liquid without leaking), as are the fuel lines. You need a regulator/vaporizer that converts the LPG liquid to a gas. Many cars that burn LPG are bi-fuel cars that can burn both gasoline and LPG in case LPG is not available. There needs to be valves and switches to handle the change from one fuel to the other.

Natural gas vehicles have the same characteristics but use yet another fuel, which is primarily methane (CH4) and always a gas. For more info see: How Natural-gas Vehicles Work

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