Wednesday, March 17, 2010

Chem Question in regards to air fuel ratios ...interesting read below.?

An automobile engine requires a carburater or fuel injector to mix fuel with air. The fuel and the air must bemixed in a particular ratio to acheive maximum efficiency in the combustion of fuel . What might happen if the fuel and air mixture is too rich ( if there is too much fuel ?) please and thank you :]
Chem Question in regards to air fuel ratios ...interesting read below.?
The ideal mixture of air and fuel is known as the stoichiometric ratio.





When this ratio is achieved, there is a exactly the right amount of fuel and air to ensure complete combustion and full utilization of the available oxygen.





If there is more fuel than air (ie: the mixture is rich) then incomplete combustion occurs and that generally results in an increase in carbon generation.





Over time, this carbon can build up on the inside of the engine's combustion chamber, piston and valves -- causing problems.





It also means you won't get the best MPG that your car is capable of.





Of course exactly how much fuel is required to create a stoichiometric mixture depends on many factors such as the density of the air (which changes with altitude and barometric pressure). With a carburetor, an engine tuned to run correctly at sea-level will run rich at altitude because there's less air available to burn the fuel in.





Modern cars have computer controlled fuel injection which addresses this problem by constantly monitoring how much air is going into the engine and whether there's any unburnt fuel or oxygen in the exhaust. By monitoring this, the amount of fuel injected can be finely tuned to ensure maximum power or efficiency (depending on where your foot is on the gas pedal).


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