* Throttle position: More throttle means more air and fuel are needed, but the ratio can shift slightly.
* Engine speed: Higher RPMs generally require a richer (more fuel-rich) mixture.
* Engine load: Heavier loads (like climbing a hill) require a richer mixture.
* Temperature and altitude: Colder temperatures and higher altitudes require adjustments to maintain the optimal ratio.
* Carburetor design and adjustments: Different carburetors have different designs, and adjustments (like needle and jet settings) significantly influence the air-fuel ratio.
Ideal Stoichiometric Ratio:
The ideal, stoichiometric air-fuel ratio for gasoline is approximately 14.7:1 (by weight). This means 14.7 parts air to 1 part fuel. At this ratio, all the fuel is completely burned, resulting in minimal emissions.
Operational Air-Fuel Ratios:
However, carburetors rarely operate *exactly* at 14.7:1. The mixture is often richer (more fuel) during acceleration and at higher loads for better power and to prevent lean misfires. Leaner mixtures (less fuel) might be used during cruising for better fuel economy, but this is often at the expense of some power. Therefore, the operational air-fuel ratio can range from roughly 12:1 to 18:1 throughout the engine's operating range. Staying within this range is crucial for engine performance and longevity.
In summary, there's no single "air and fuel ratio of carburetor". It's a dynamic range dependent on many factors, with the ideal stoichiometric ratio serving as a target, but rarely the constant operational value.
