Fuel temperature estimation system

A fuel temperature estimation system, the fuel temperature estimation system being configured to estimate a fuel temperature variable on a fuel temperature, which is a temperature of fuel, for an engine apparatus including a fuel injection valve and a fuel supply device having a fuel pump that supplies the fuel in a fuel tank to a supply pipe connected to the fuel injection valve, and comprising:

• a storage device configured to store a first mapping that receives, as an input, first input variables including a previously estimated value for the fuel temperature variable, a pump variable on a state of the fuel pump, a first engine variable on a state of an engine, and an outside air temperature variable on an outside air temperature, and outputs the fuel temperature variable;
• and
• an execution device configured to acquire the first input variables and estimate the fuel temperature variable by applying the first input variables to the first mapping, wherein:
• the first mapping includes, as the first input variables, a heat quantity variable on a heat quantity of the fuel, and a heat capacity variable on a heat capacity and heat transfer of the fuel;
• for the heat quantity variable, a fluctuation amount per predetermined time is input;
• and
• for the heat capacity variable, an average value per predetermined time is input.