Three Range Rover diesel hybrid prototypes have completed what was arguably the toughest engineering sign-off test yet, crossing 13 countries in 53 days from Solihull in England to Mumbai in India, on the world's first hybrid expedition along the historic Silk Road.
Hostile conditions along the way included tar roads riddled with potholes deep enough to swallow a motorcycle, dusty desert trails in 43-degree heat and many kilometres of mud and gravel tracks and cattle trails - as well as river crossings, passes clinging to the edges of mountains partly blocked by rock falls, the thin air of extremely high altitudes and the dense and erratic traffic of Chinese and Indian roads.
The Silk Trail 2013 expedition was the final validation test for the Range Rover hybrid before it was signed-off for production. From Land Rover's home in Solihull it took the three pre-production prototypes - loaded with luggage, camping gear, food, medical equipment, and aerodynamically-unfriendly roofracks carrying spare wheels, tyres and jerry cans of fuel - through France, Belgium, Germany, Poland, the Ukraine, Russia, Kazakhstan, Uzbekistan, Kyrgyzstan, China (including Tibet), Nepal and India.
2500 YEARS OF MERCHANTS, MISSIONARIES AND MERCENARIES
For much of this distance the expedition followed the legendary Silk Road trading routes that first connected Asia with Europe more than 2500 years ago. Overnight halts were made in hotels, hostels and tents at many of the same staging posts visited all those years ago by Silk Road merchants, missionaries and mercenaries.
Where the north and south Silk Roads split, near the remote city of Kashgar in north-western China, the expedition pioneered a mountainous route never previously completed by a foreign vehicle and never previously seen by any westerner - the Xinjiang-Tibet highway, which took it to more than 5300 metres above sea level.
WHERE INTERNAL-COMBUSTION POWER VANISHES INTO THIN AIR
The expedition spent a whole week at altitudes above 3350 metres, where the oxygen content in the air is reduced from the 21 percent found at sea level to as little as 10 percent, making movement more difficult for humans and internal combustion engines.
The hybrid Range Rovers' 35kW electric motors, however, were unaffected, delivering maximum torque at zero revs to help get the TDV6 three-litre turbodiesels going when the going got really tough. Although altitude, mud and rocky roads played havoc with the expedition's average fuel consumption, on the less challenging sections the hybrids typically used about eight litres per 100km.
STATISTICS REFLECT JUST HOW TOUGH THE GOING WAS
Over nearly eight weeks on the road data loggers fitted to each car sent back more than 300 gigabytes of detailed technical records to the engineering team at Gaydon in the UK - not to test the reliability of the mechanical components, which are already well proven, but to fine-tune the calibration of engine and transmission software for seamless performance in all terrains, extreme temperatures and altitudes.
Their statistic, however, reflect just how tough the going was. The expedition's three Range Rover hybrids and four support vehicles between them suffered 15 punctures, four rims damaged by monster potholes, and four windscreens cracked by stones thrown up on loose surfaces.