Sheddick's MAN goes quietly
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by Colin Sowman I MAN trucks have been available on the Continent with silencing packages for four years, but the first right-handdrive versions have only just gone into service.
It was not a wish to keep the valleys of Wales quiet that enticed Sheddick Transport to fork out the thick end of g1,000 for a 'silence' package on each of its nine new MAN17.422FLT EC0.420s.
While the noise reduction will doubtless please residents round Sheddick's base, the kits were bought to comply with noise regs in Austria.
Trucks are not allowed into Austria after 22:00hrs unless they are certificated to emit less than 78dB(A).
From the start of next year the stakes get even higher when the Austrians introduce the ECO Points system. Operators transiting Austria will be allocated ECO points and given one stamp for each point.
Each time a vehicle goes into Austria 16 stamps will have to be "paid" even if it's running empty. But vehicles which meet low noise and exhaust emission requirements will pay less in these stamps and could be entitled to twice the number of crossings.
Sound deadening on the MANs starts with the engine block being reinforced to dampen vibration, and "noiseoptimising the combustion". MAN also encapsulates the engine and the lower half of the
gearbox with a steel guard extending from the bottom of the chassis rail under the engine and gearbox. The guard is lined with sound deadening felt; a small removable panel facilitates oil changes.
A vertical stack exhaust system is fitted with a modified silencer. All this, and low-noise tyres, enables the MAN to scrape under the 78dB(A) limit. The 309kW (420hp) engine is from MAN's ECO range and meets the Euro-1 emissions limit.
At tickover bystanders will be subjected to 67.2dB(A) of noise: towing a loaded tri-axle semi trailer with no noise suppressing measures boosts drive-by noise to 82.5dB(A) Sheddick's vehicles have a 3.4m wheelbase and pull 13.6m trailers through a kingpin set at 1,600mm. This brings the trailer very close to the back of the cab, further deadening the note from the exhaust stack. Externally the only obvious sign of the MAN's green credentials is the large green L-plate specified by the Austrian authorities; closer inspection reveals "silent" badges on the doors.
The inside of the cab is identical to a standard model and although the engine does sound quieter than usual at 58.9dB(A), what really impressed us was the exceptionally low noise level out on the road. Freighted to almost 36 tonnes and putting hard up a motorway hill at 96kmili (60mph) in top gear the noise meter registered 70.5dB(A) in the cab.
On paper this represents a ldB(A) reduction (the decibel scale is logarithmic, a 3dB rise equates to a doubling in noise level), but that belies the scale of MAN's achievement. Engine noise is reduced to a muffled growl allowing the turbo whistle
— no noisier than in other M90s
— to take over as the most noticeable sound, particularly when the engine's working for its living.
The sound deadening package is designed to reduce lowfrequency noise, perhaps it isn't surprising that the highfrequency turbo whistle penetrates through to the cab.
Early lownoise MANs suffered a slight power loss but not any more: the silent 17.422 churns out its full quota of 309kW (414hp). With all those horses under your right foot the splits in the lower half of the 16-speed ZF box are rarely needed. Getting underway on the level is easily achieved in 3L, and once rolling the bottom half of the box need not be visited at all.
In the past we have commented on the quality of MAN's driving environment. Not only does the "Silent" vehicle take this one step further: it improves the environment for other road users and nearby residents, too.