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Difficulty: EasyFuel and Air Intake Systems

In a standard gasoline engine operating under normal cruising conditions, what is the ideal (stoichiometric) ratio of air to fuel by weight?

  1. A
    1 part air to 14.7 parts fuel
  2. 14.7 parts air to 1 part fuelAnswer
  3. C
    1 part air to 1 part fuel
  4. D
    4 parts air to 1 part fuel

Answer

14.7 parts air to 1 part fuel
The ideal or stoichiometric air-fuel ratio for a standard gasoline engine is 14.7:1 by weight, meaning 14.7 pounds of air are metered for every 1 pound of fuel to achieve complete combustion.

Step-by-Step Solution

1
Identify the chemical requirement for complete gasoline combustion.
Gasoline requires approximately 14.7 pounds of air to burn 1 pound of fuel completely.
This exact stoichiometric proportion allows all oxygen and gasoline molecules to react fully without leaving unburned fuel or excess oxygen.
2
Express the relationship in standard air-to-fuel proportion format.
The proportion is written as 14.7:1 (14.7 parts air to 1 part fuel by weight).
Air always constitutes the overwhelming majority of mass entering the intake manifold relative to liquid fuel.

Key Concept

Stoichiometric Air-Fuel Ratio
Estimated Time:45s
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Topics

Fuel and Air Intake Systems

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