We have to start with the turbocharger. The turbine is driven by the exhaust gas of the engine. The temperature of the exhaust gas plus the speed of tens of thousands of revolutions of the turbine make the temperature of the turbine work extremely high.
On the one hand, the air pressurized by the turbocharger is heated by the heat conduction of the turbocharger itself, and on the other hand, it is heated by the compression of the air, and the temperature of the air finally reaching the combustion chamber becomes very high.
The lower the air temperature, the greater the air density, the higher the oxygen content in the same volume of air, and vice versa.
However, after being heated by the turbocharger, the air density is greatly reduced, the charging efficiency is low, and the oxygen content is low, which ultimately leads to a decrease in engine power.
Seeing that the power enhancement method that has been worked out so hard is offset by the excessively high intake air temperature, which is really not cost-effective. Therefore, engineers came up with a solution, which is to reduce the temperature of the intake air, and the intercooler was born.