The function of intercooler in turbocharged engine

Nowadays, many cars have engines with a prominent "T" symbol, which proves that it is a turbocharged engine. We all know that turbocharged engines add a turbocharger device on the basis of the original engine. During operation, the excess energy generated by the turbocharger itself must be reasonably conducted out, which requires a device to "neutralize energy" with it, and this is the intercooler.

The intercooler will increase air resistance, causing a decrease in the pressure of the boost air, resulting in a reduced boost effect and slower engine response. However, compared to the role of the intercooler in increasing engine power, this effect is insignificant.

Air cooling or water cooling?
There are only two methods to cool the air. One is to cool down by the cold air that hits the vehicle head-on while driving, and the other is to use water cooling. The principle of the former is the same as the radiator of our household refrigerators and air conditioners, which allows air to pass through pipes to increase the contact area between the pipes and the surrounding air, and then cools it down through the surrounding air. An air-cooled intercooler placed above the engine.
Water cooling is exactly the opposite of air cooling. It is to place a cooler into the intake duct and allow the pressurized hot air to flow through. And in the cooler, there is continuous flow of cooling water, which takes away the heat from the pressurized air.

The solid line represents the flow of air, and the dashed line represents the flow of cooling water
Firstly, following the previous topic, when air is compressed by a turbocharger, its temperature will increase, which is a fundamental physical principle. How much will the temperature of the gas increase after pressurization? This depends on the working condition of the turbocharger. The higher the speed, the greater the boost pressure, and the greater the temperature rise. Generally speaking, it can rise by about 40-60 degrees. Coupled with the original temperature of the air, the boosted gas is already very hot.

The impact of high-temperature gases on engines mainly lies in two aspects: firstly, the volume of air increases, which means that the amount of air inhaled by the engine decreases; The second point is even more important, as high-temperature air is particularly detrimental to engine combustion, reducing power and worsening emissions. Under the same combustion conditions, for every 10 ℃ increase in the temperature of the charge air, the engine power will decrease by approximately 3% to 5%. This problem is very serious, as the increased power that has been worked on will be offset by the high air temperature. To solve these problems, we need to cool the boosted air again before sending it into the engine. And the component that bears this heavy responsibility is the intercooler. The intercooler sounds cool, but its principle and structure are not much different from the radiators of our household refrigerators and air conditioners.
Side effects: engine response speed slows down, turbo lag becomes severe. Why do we need an intercooler.

Generally speaking, the larger the intercooler, the smaller the airflow loss inside and the higher the cooling efficiency. The longer the airflow stays inside the intercooler, the better the cooling effect. However, the intercooler is like increasing the volume of the intake duct, and the compressed air generated by the turbocharger must first fill this volume before it can produce a boost effect. If used in turbocharging, the direct manifestation effect is that turbo lag becomes severe; Even machines with mechanical supercharging can cause a slower engine response.
On the other hand, due to the need for pressurized air to flow through various pipelines, the resistance increases, and its boost pressure will definitely be partially weakened. However, this weakening only occurs for a short period of time after stepping on the accelerator, because after the pressure of the boost air is weakened, sufficient pressure will be re established in the sealed space from the intercooler to the intake valve until the pressure relief valve opens. Therefore, the performance will still be slower engine response, and the lag phenomenon of turbocharging will become more severe.

The intercooler will make the turbo lag more pronounced, but it cannot be ignored, so how to balance cooling efficiency and pressure maintenance is a headache for engineers. The fundamental method is to reduce the volume of the entire intake pipe, decrease pipe resistance, and shorten the intake pipe. Therefore, the intercoolers we see are often closely attached to the engine, rather than being as far away from the engine as the radiator. High turbocharged and large displacement engines often require a large and medium-sized cooler due to their large intake volume and high temperature. The most common way to see a large intercooler is to place it on top of the engine compartment, which can be cooled by opening an air inlet on the engine hood and using the cold air that hits from the front. This method can be seen in many cars, such as the Wing Leopard STI and MINICOOPERS. The advantage of placing it above the engine is its compact structure and short pipes, making it very suitable for small and modified cars. But this arrangement is too close to the engine and will be affected by engine heat.
MINICOOPERS and YIBAO STI both have openings in the engine hood for intercooler cooling.

Another arrangement is to place the intercooler under the front of the car grille. This method fully utilizes the incoming cold air for heat dissipation, but the pipeline is too long and the layout is more complex. Due to being closer to the ground, there is a greater likelihood of damage from ground sand and gravel.
For both cooling methods, they belong to external air cooling and are suitable for large intercoolers. The current trend is towards low boost engines that do not require large intercoolers. In order to make the engine more compact, many engines currently use water cooling by placing a cooler in the intake duct, which cools the air as it passes through. The structure is very compact.
The intercooler used by Volkswagen 1.4TSI

The intercooler is a very important component in turbocharged engines, which can effectively reduce air temperature and increase engine power. In addition to lowering the temperature of the air, we also need to cool down the turbocharger and control the boost pressure.

The familiar Volkswagen 1.4T turbocharged engine uses this method, while Audi's mechanical turbocharging also uses this form of cooling, with a relatively compact structure. Due to the fact that this type of intercooler is completely installed internally, it is less susceptible to damage from dust and sand.