In this report a presentation is given of experiments and thermo-chemical calculations on a pulse detonation engine, equipped with a pre-detonator. The main results are the following: · The possibility to initiate a detonation in the pre-detonator is only weakly dependent on the equivalence ratio, F, of fuel and oxidator. · The choice of insert used in the main chamber has an impact on the detonability. With one of the tested inserts, detonation was in some cases achieved even without the addition of excess oxygen. The least amount of excess oxygen needed to ensure detonation was found to be 1.9 % (by partial pressure). · Detonation failure and late DDT seems to have a limited impact on the mean thrust and on the specific impulse. Hence, in a multi-pulse engine a few of such "glitches" will probably be tolerable. · Thermo-chemical calculations using the Cheetah-code can be used to predict the detonation velocity and the thrust generating pressure, especially if the engine dimensions are large enough and a complete detonation is achieved. · In an acetylene/air driven PDE, calculations show that the equivalence ratio, F, should not exceed 1.7. The fuel efficiency will increase with decreasing F. However, if F is to small (<1) the impact on thrust and detonation velocity is rather strong. Furthermore, the detonability decreases as F decreases.