Swirl valves are small throttle valves located in the intake manifold of modern diesel and gasoline engines, they are designed to help regulate the fuel/air ratio, improve emissions and help generate better torque at low engine speeds . Under light engine load, the flaps close, causing air to swirl into the combustion chamber. Swirl aids combustion and helps improve emissions and generate more torque. After 2000 rpm the flaps are normally activated to the fully open position and have very little effect on engine performance and emissions.
The EGR is located before the swirl flaps and is one of the main reasons for their damage, the accumulated soot together with the oil vapors from the ventilation system reduces the size of the intake manifold and covers the flaps. This hinders their free movement and they get blocked. Damage to the swirl flaps can have bad consequences for the engine as debris falls into the valve openings and blocks them causing collision with the pistons. Debris often enter the cylinder itself, causing damage to the pistons, valves and cilinder head.
Removal is done by programming the ECU and modifying the software. In some cases the flaps are physically removed, in other cases where the mechanical condition of the flaps is good and the failure is due to an electronic actuator the actuator function can be disabled and the flaps remain in place.
The removal has no negative consequences with the software modification, their work is compensated and the car runs with its full power.