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Air/Fuel Mixture | Engine Power

Regardless of the fuel type used during the combustion, combustion efficiency depends on having the correct amount of air mixed with the correct amount of fuel. The ideal air/fuel ratio for most operating conditions of a gasoline engine, which most of our engines are today, is approximately 14.7 pounds of air mixed with one pound of gasoline. This provides a ratio of 14.7 to 1.

Because air is so much lighter than gasoline, it takes nearly 10,000 gallons of air mixed with one gallon of gasoline to achieve an air/fuel ratio of 14.7 to 1. This is why proper air delivery is as important as fuel delivery.

When the mixture has more air than the ideal ratio calls for, the mixture is said to be lean. Ratio of 15:1 to 16:1 provides the best fuel economy from gasoline engines. Mixtures that have a ratio below 14:7 to 1 are considered rich mixtures. Rich mixtures (12 to 13:1) provide more power production from the engine but greater fuel consumption.

If the combustion process is complete, all of the gasoline will be completely combined with the available oxygen. The ratio of air to fuel that accomplishes this is referred to a stoichiometric. The stoichiometric quantities for gasoline are 14.7 parts of air per 1 part gasoline. Different fuels have different stoichiometric ratios (diesel, ethanol, methanol).

In order to control the proportion of fuel to air in the air/fuel charge, the fuel system must be able to measure the amount of air entering the engine. Sensors on the engine do just that. Used on cars today is the mass airflow sensor (MAF), the manifold absolute pressure (MAP) sensor and the oxygen sensors (02).The vehicles computer uses the information gathered from these sensor to determine the amount of fuel that is needed to provide the optimum fuel ratio.

If you can cram more air (and therefore fuel) into a cylinder of a given size, you can get more power from the cylinder. Turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder. The power generated by the internal combustion engine is directly related to the amount of air compressed in cylinders. In other words, the greater the compression in the cylinders (within reason), the greater the output of the engine. The two processes of artificially increasing the amount of airflow into the engine are known as turbocharging and supercharging.

Turbochargers do not require a mechanical connection between the engine and the pressurizing pump to compress the intake gases. Instead, they rely on the rapid expansion of hot exhaust gases exiting the cylinders. These gases spin the turbine blades of the pump. Because exhaust gas is a waste product, the energy developed by the turbine is said to be free since it theoretically does not use any engine’s power that it helps to produce.

Superchargers are air pumps directly driven by the engine’s crankshaft by a belt. They improve horsepower and torque by pumping extra air into the engine in direct relationship to crankshaft speed. This positive connection provides for instant power response.

Check out E-Ram electric supercharges. An inexpensive way to put a supercharger on your car.

Air/Fuel Mixture | Engine Power

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