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Doubts over air-management kit fuel-saving figures
Page 26
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I DON-1 doubt the scrupulousness with which Kevin Upson and his colleagues at Mercedes-Benz carried out their air-management assessment tests, nor the improvements in fuel efficiency they recorded (CM 12 April).
I assume, however, that to maintain a constant 90krn/h for 350km, the vehicle must have been run around a test track, rather than on motorways where unimpeded forward progress at the legal maximum speed for any length of time is impossible.
Under real-life conditions, as road speed is forced down by traffic density. streamlining has progressively less effect on fuel economy.The consumption figures quoted for the Axor after it had returned to fleet service are so stunning for a 44-tonner -10.2mpg even without the air deflector kit that it cannot have been up to its plated gross weight for much of the time.
The 14% consumption improvement Mr Upson says the operator recorded under those fleet conditions, with the aerodynamic fitments in place, is also stunning-and hard to explain. It suggests numerous 'rogue' variables between the 'with' and 'without' Axor rigs, particularly in average actual gross weight.
In short I remain unconvinced -not of the benefits of a welldesigned air-management package, but of their effect under UK operating conditions.
Alan Bunting by e-mail