Hydrogen 7 features a 6.0 L V-12 engine with hydrogen port
fuel injection that is based on BMW’s production 12-cylinder
engine for the BMW 760 sedan. The car employs a variable
air–fuel ratio lean-burn strategy (qualitative control) at low
and medium engine loads and switches to stoichiometric
operation (quantitative control) at high engine loads. This
strategy avoids the NOX critical operating regime with air
fuel ratios 0:5 G G 1 (see Fig. 5) and a catalyst is used to
reduce NOX emissions in stoichiometric operation. Approximately
8 kg of hydrogen (equivalent to 8 gallons of gasoline
in terms of energy content) are stored on-board the vehicle
in a cryogenic tank that is located in the trunk allowing for a
range of 200 km on hydrogen. The vehicle is equipped with a
dual-fuel system allowing for operation on hydrogen or
gasoline with an additional range of 480 km on the
conventional fuel [26]. Emissions tests of a dedicated
mono-fuel version of the Hydrogen 7 vehicles showed the
low emissions potential of hydrogen powered vehicles. With
a dedicated after-treatment design featuring two catalysts
(one for stoichiometric operation and one for reducing
NOX peaks that occur when switching from lean to
stoichiometric operation) the vehicle achieved drive-cycle
NOX emissions that were approximately 0.0008 g/mi,
which is equal to 3.9% of the Super Ultra Low Emissions
Vehicle (SULEV) limit [27].