For the future design of environmentally-friendly spare ignition engines (Si-engines) more detailed knowledge of the fundamental physical phenomena in the temporal course of mixture formation processes is essential. One possible way to obtain the required information is the visualization of the two-phase flow within a real intake manifold of a Si-engine under working conditions coupled with a fundamental flow analysis and numerical modelling. In the present paper two visualization methods are applied:
First, a fiber optic probe is employed inside an intake manifold of a 1.8-litre-engine with a multi-point injection system. Then, for a more detailed analysis, a transparent intake manifold of an identical geometry is used. Combined with a cycle-resolved laser light-sheet technique the crank-angle dependent behavior of the spray and liquid film inside the intake manifold is visualized. Based on the observations, conclusions can be drawn, which effects in the intake manifold are of dominant importance determining the mixture preparation process and which may be negligible.