The AVL 513D Engine Video-Scope from AVL LIST GmbH (www.avl.com) is a fully digitized video system for visual analysis of engines. It allows visual access to almost any part of the cylinder without affecting the engine's operation. A digital camera mounted on endoscopes delivers high-resolution images and is triggered via the crank angle at an accuracy of 0.1°. The recorded images can be analyzed offline using software developed for AVL. A representative combustion cycle can be calculated and simulated. For diesel engines, the temperature distribution of the flame can be represented by thermovision images. The distribution gives insight into the formation of nitrogen oxide and soot concentration during combustion.