The NOx reduction technology developed by Wärtsilä. Pressurized water is added to the intake air after the turbocharger to reduce the combustion temperature and thereby the formation of NOx. The water evaporates immediately and enters the cylinders as steam, lowering the combustion temperature. A water mist catcher prevents water in liquid state from entering the cylinders. The NOx reduction is up to 40%, and the water consumption is about two times the fuel oil consumption.