Proportional integral derivative (PID) controllers are important and widely used tools of system control. In the practical context of combustion engine simulations, we face the problem of tuning multiple coupled PID controllers, while not being provided with any information about the controlled system. Therefore, we formulate the problem as a black-box optimization problem. We derive a suitable objective function and, based on its properties and practical limitations, we choose an appropriate optimization algorithm: Covariance Matrix Adaptation Evolution Strategy (CMA-ES). The algorithm is calibrated using a simple testing model but its usability is finally verified on models of real-world engines.