Pressure Chamber
WARNING: This page does not describe the selected car, but rather 151 other vehicles, including the 2006 BMW X5, 2006 BMW M3, 2006 BMW 330Ci, 2006 BMW 325Ci, and 2005 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
The propellant charge in the chamber is a mixture of approximately 13.5% Hydrogen and 86.5% Oxygen under pressure.