Fuel cooling
The fuel (back) cooling is used to inject fuel, which runs cool previously from the injector pump back to the tank. This is particularly useful for vehicles with direct petrol injection when the tank is almost empty in summer, in order to prevent excessive heating and evaporation of the remaining tank contents.
In modern injection systems , the fuel is compressed to up to 2500 bar and warms up considerably. Fuel that does not get into the combustion chamber is returned to the tank via the leak fuel line. To cool it down before refluxing, it runs through a heat exchanger.
Racing
In racing, the extreme cooling of the fuel before it is added to the vehicle tank is a popular method to increase the density and thus the fuel mass in the fuel tank. When the temperature drops from +20 ° C to –20 ° C, the fuel contracts by around 0.044 l / l (γ = 0.0011 [1 / K]). With a tank volume of 100 l, about 4.4 l more can be filled.
Tuning measure
The fuel cooling installed by the manufacturer in the return of the leak fuel line must be distinguished from tuning measures of the same name in the fuel supply . The latter should increase the injected fuel mass through cooler and thus denser fuel and thus increase the power. Modern engines with lambda control then reduce the injected volume accordingly so as not to run out of the lambda window , which prevents the desired effect. The tuning measure is therefore ineffective in modern engines with lambda control.