You can calculate the fuel consumption of a particular car without taking any measurements. Fuel consumption calculation methods based on measuring fuel consumed per 100 km often give conflicting readings. However, fuel consumption is a strictly defined value and is calculated based on knowledge of the laws of physics.
It is necessary
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Instructions
Step 1
When the internal combustion engine is operating, the combustion of the air-fuel mixture with the release of heat occurs. Thermal energy is converted into mechanical energy and makes the car move. The optimal composition of the air-fuel mixture for gasoline engines: 14.7 grams of air per 1 gram of gasoline. In other words, 14.7 grams of air contains the necessary and sufficient amount of oxygen to burn 1 gram of fuel.
Step 2
The engine will not be able to operate normally on either too rich or too lean and will eventually stall. For normal engine operation, an optimal (close to ideal) fuel mixture is required. Carburetor engines operate on a mixture enriched by 3-5%, injection engines at 3-8% lean mixtures. Either way, the engine operates in a very narrow range of fuel mixtures, and will stall if given 10% more or less fuel.
Step 3
Fuel consumption is the amount of fuel burned in the air-fuel mixture. It is not difficult to calculate the amount of fuel consumed by the engine. The cylinder volume of the engine is taken as a basis - this is the amount of the fuel mixture that will burn in the engine in one cycle (2 revolutions). Dividing the engine displacement in half gives the same value per revolution. For example, a BMW 320 with a 2000 cc engine burns 1 liter of the mixture in one revolution.
Step 4
To calculate the amount of fuel contained in 1 liter of the mixture, the weight of air (1.2928 kg per cubic meter under normal conditions) and the optimal mixture ratio (14.7: 1) are used.
1.2928 / 14.7 = 0.088 Consequently, one liter of the optimal air-fuel mixture contains 0.088 grams of fuel. Next, you should multiply the amount of the combustible mixture per revolution by the fuel content in this mixture. In our example, this will be 1 * 0.088 = 0.088 grams. This value is the fuel consumption of the engine per revolution.
Step 5
Fuel consumption is calculated by multiplying by the number of revolutions. For our example, at idle speed (700 rpm), the BMW engine will burn 0.088 * 700 = 61.6 grams of fuel. On the highway, when the engine is running at 2000 rpm, the fuel consumption will be 0.088 * 2000 = 176 grams per minute or 176 * 60 = 10560 grams per hour. During this time, this car will travel about 60 km.
Step 6
From all this it is clear that the fuel consumption of the engine is directly proportional to its volume. The on-board computer installed on the car will more accurately calculate and show the fuel consumption.
Step 7
However, the air-fuel mixture is not optimal in all operating modes. It is depleted when braking by the engine, briefly enriched with a sharp set of revolutions and when the engine is running under load. The engine warms up at high speeds and with a rich mixture. Fuel consumption in these modes will differ from the calculated one.
