The engine: series production 12 cylinder specially adapted for hydrogen
The "heart" of the H2R Record Car is based on BMW's
top-of-the-range power unit, the six-liter 12 cylinder. It is able
to run on hydrogen fuel through the adjustment of engine management as well
as the fuel/air mixture formation components.
The most significant differences in terms of the engine's structural
components are the hydrogen injection valve and the choice of materials for
the combustion chambers: Contrary to the production engine with fuel
injected directly into the combustion chambers themselves, the injection
valves in the hydrogen engine are integrated in the intake manifolds. And
for the specific speed record requirements to be fulfilled in this case, the
hydrogen combustion engine was designed and built for single-mode operation
running exclusively on hydrogen.
This allowed the engineers to set up and tune the engine specifically for
hydrogen requirements, for example by using special valve seat rings made of
an appropriate material. The reason for this necessity is that hydrogen does
not have the lubricating effect of a conventional gasoline/air mixture. And
it is worth noting in this context that this need to cope with a lower level
of lubrication already arose in the past when introducing unleaded gasoline,
production engines since then being built with even stronger and more
Hydrogen providing enhanced efficiency
A fundamental consideration is that the combustion properties of hydrogen
are quite different from those of gasoline or diesel: While hydrogen burns
faster than conventional fuels under normal air pressure, the combustion
temperature is slightly lower than in the case of gasoline.
Inside the engine the high combustion speed of the hydrogen/air mixture
generates a higher temperature than in an engine running on gasoline. Engine
management of the BMW H2R Record Car has been modified accordingly, the
hydrogen/air mixture not being ignited until the piston reaches top dead
centre, thus ensuring maximum output. With a gasoline/air mixture burning
relatively slowly, by comparison, the mixture must be ignited at an
increasingly early point as a function of engine speed, the pressure peak
thus being reached just as the piston starts to move down.
A significant advantage of the higher combustion pressure of the
hydrogen/air mixture is that the generation of more power from the same
amount of energy means a higher degree of efficiency.
As desirable as the high standard of ignitability of hydrogen within the
engine may be, it naturally requires a great deal of attention outside of
the combustion chamber. To avoid misfiring, for example, BMW's engineers
have developed a specific gas cycle and injection strategy, with BMW's VANOS
infinite camshaft adjustment masterminding the share of residual gas
according to specific, on-demand requirements:
Before the hydrogen/air mixture is able to flow into the cylinders, the
combustion chambers are cooled by air to ensure that the fuel/air mixture is
not able to ignite in an undesired, uncontrolled process.
VALVETRONIC providing optimum conditions for hydrogen drive
Exclusive to BMW, VALVETRONIC technology serving as a standard feature to
mastermind the valves on the 12 cylinder gives the Company's engine
development specialists an ideal tool for controlling this demanding gas
charge cycle. VALVETRONIC controls not only the duration of valve movement,
but also the actual valve lift. This effect is provided by an intermediate
lever between the camshaft and the two intake valves on each cylinder
infinitely modified in its position relative to the camshaft by an
additional eccentric shaft operated by an electric motor. Depending on the
position of this eccentric shaft, the lever transforms the "hump" on the
cams into a larger or smaller valve movement.
VALVETRONIC is based consistently on BMW's infinite camshaft adjustment
process. Already well-known under its trade name VANOS, this system is an
integral part of the VALVETRONIC concept. Incorporating a hydraulically
controlled adjuster unit in the camshaft drive, VANOS modifies the beginning
and end of the valve opening period, fully variable valve management serving
to adjust the gas charge cycle in the 12 cylinder power unit perfectly to
the requirements and characteristics of hydrogen drive.
Special injection valves for hydrogen power
With hydrogen being injected into the intake manifold as late as possible,
the injection valves have to meet very demanding requirements. Hence, the
valves are a trendsetting new development for BMW. And since gaseous
hydrogen takes up a larger volume per unit of energy than liquid gasoline,
the hydrogen injection valves are larger than conventional injection valve
A further point is that the valves have to cover a far wider range of
different features and requirements, operating under all kinds of system
pressure levels and with injection periods ranging from very short to
relatively long. One of the main objectives in developing the valves was to
inject exactly the right amount of hydrogen required into the intake
manifold within a very short time-frame at very high engine speeds and under
A clean mixture formation process: less fuel consumption under part load,
extra power under full load
Under full load the 12 cylinder power unit runs on a fuel/air mixture of
lambda = 1. This is exactly the same mixture we also find on a
state-of-the-art gasoline engine, the mixture which, in principle, offers
the highest and most efficient power output in a combustion engine. Under
part load - again a significant benefit offered by hydrogen - the engine
runs efficiently in the lean burn mode with surplus air.
Under specific conditions, that is with a specific fuel/air mixture, the
combustion of hydrogen leads to the generation of nitric oxides. This
mixture "slot" starts slightly above lambda = 1 and extends to the range of
lambda > 2.
The simple solution to this problem is to leave out this mixture "window"
altogether, since it is not required for running the engine. Hence, the fast
management system controlling the BMW hydrogen engine skips this operating
range completely, thus avoiding NOx emissions in the process. As a result,
the H2R Record Car is just as powerful as a conventional gasoline-engine
car, while at the same time its emissions are limited, for all practical
purposes, to nothing but steam.
The fuel system featured in the BMW H2R Record Car is based on a proven
series development concept. Fuel is filled into the tank of the H2R
prototype at a mobile hydrogen filling station through a manual tank
coupling. The vacuum-insulated, double-walled tank has a capacity of more
than 11 kilos of liquid hydrogen and is fitted next to the driver's seat. A
total of three valves ensures optimum safety, the operating valve on the
tank opening at a pressure of 4.5 bar.
Two additional safety valves rule out any dangerous consequences of possible
leaks in the jacket around the tank serving to keep the hydrogen at the low
temperature required, opening up as soon as pressure within the tank exceeds
the limit of 5 bar. This double-redundant safety system guarantees optimum
safety at all times, ensuring that the hydrogen tank will not burst as a
result of excess pressure.
Gas pressure builds up in the fuel supply system simply because of the
rising temperature of the cryogenic, liquid hydrogen in the tank and is kept
at an operating pressure of approximately 3 bar by a tank pressure
controller. Then the coolant running within the 12 cylinder power unit warms
up the hydrogen gas in a heat exchanger to ambient temperature.
Additional valves monitor the pressure of gas in the fuel pipes leading to
the engine: Cold low-temperature valves inside the tank control the removal
of hydrogen from the tank itself. Should any of the pre-flow pipes develop a
leak, with supply pressure dropping below 0.4 bar, the fuel supply valves
close automatically, disconnecting and sealing the tank off from its
surroundings. The supply pipe can also be interrupted manually by an
To maintain optimum supply pressure on the injection valves at all times –
especially as this pressure may vary as a function of driving conditions -
engine management reduces pressure in the supply pipe to approximately 1.2
bar by means of a control valve fitted specifically for this purpose.
This comprehensive safety system featured in the H2R Record Car is
supervised additionally by a telemetric system of the same type as in
Formula 1. Four hydrogen sensors fitted at neuralgic points - for example in
the tank itself and around the tank coupling - recognize any leakage
immediately and inform the driver accordingly.
Chassis and suspension
Focusing on the structure and chassis of the BMW H2R Record Car, the
engineers and development specialists at BMW Forschung und Technik GmbH used
series components carried over from a sophisticated, thoroughbred BMW sports
car--the monocoque aluminum spaceframe--as well as the entire chassis and
suspension system. High-strength aluminum structure panels using the
advantages of aluminum as a particularly light material resistant to
corrosion fill in the open spaces between the extra-large extrusion-pressed
profiles giving the car its stable "skeleton".
The result for the driver is an absolutely excellent, direct driving
experience without the slightest vibration or body "tremble".
The front suspension is based on a double-wishbone spring strut front axle
together with rack-and-pinion steering, aluminum track control arms, a
tiebar, and an anti-roll bar. The front axle subframe is formed by a welded
aluminum structure made up of extrusion-pressed profile bars and plates
holding all front axle components and bolted to the body at six points. The
track control arm made of forged aluminum comes complete with two ball
joints in the interest of precise wheel guidance and directional stability.
Wheel guidance and stability at the rear is provided by an integral
four-dimensional axle, a multi-arm principle patented by BMW and rounded off
in this case by an anti-roll bar. Optimum road contact and safety, finally,
is ensured by tires measuring 245/40 x 19.
The bodyshell: outer skin made of carbon fiber
BMW's designers gave the H2R Record Car a truly unique body.
Measuring 5.40 meters in length and 2 meters in width, the body of the car
is designed through and through for optimum streamlining. And to reach
record speeds, the frontal area measures just 1.85 square meters and the
drag coefficient is a mere 0.21. At the rear a 20-centimetre-long diffuser
prevents air swirl behind the car, which might potentially slow it down.
The side profile and sheer length of the H2R prototype also serve to ensure
stable driving characteristics at very high speeds. Like on a
racing car, the outer skin is made of carbon-fiber-reinforced plastic
offering the optimum combination of superior stiffness and low weight:
Overall weight of the H2R with a full tank and the driver at the wheel is
1560 kg or 3440 lb.