```
Fuel consumption (kg/hr) = (Air/Fuel ratio * Air flow rate (kg/hr)) / 3600
```
To calculate the air flow rate, you need to know the engine's displacement (in liters), the RPM, and the volumetric efficiency. The volumetric efficiency is a measure of how much air the engine can actually take in compared to its theoretical maximum. A typical volumetric efficiency for a gasoline engine is around 80%.
Once you have these values, you can calculate the air flow rate using the following formula:
```
Air flow rate (kg/hr) = (Engine displacement (L) * RPM * Volumetric efficiency) / 120
```
Now that you have the air flow rate, you can plug it into the first formula to calculate the fuel consumption per hour.
Example:
An engine has a displacement of 2.0 liters, an RPM of 3000, and a volumetric efficiency of 80%. The air/fuel ratio is 14.7:1.
```
Air flow rate (kg/hr) = (2.0 L * 3000 RPM * 0.80) / 120 = 40 kg/hr
```
```
Fuel consumption (kg/hr) = (14.7 * 40 kg/hr) / 3600 = 0.163 kg/hr
```
Therefore, the fuel consumption of this engine is 0.163 kg/hr.
