Steyr goes hush-hush
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• Steyr Trucks has introduced a low-noise 231kW (310hp) six-cylinder diesel, completing a range of low noise engines to meet proposed Austrian motorway restrictions.
Concerned by noise pollution on its three major motorway routes, the Austrian government has proposed a night time noise limit of 78dB(A) for trucks under 152kW (204hp), and 80dB(A) for trucks above that figure.
Steyr has already built lownoise versions of its medium range (102-157kW) vehicles. Last year it produced low-noise versions of its 180kW (240hp) and 209kW (280hp) tractor engines, and now it will offer a partially-encapsulated version of the largest six-cylinder engine with a maximum noise level of 80dB(A).
The existing vee-eight engines produced by Steyr, but not offered in the UK, will not be offered in low-noise versions. They are considered too heavy for the current truck market, and Steyr hopes to supersede them with longer stroke versions of its sixcylinder engine within two years.
It already has stroked versions of the six-cylinder engines producing over 328kW (440hp) with four valves per cylinder and injection pressures of up to 1,300bar. Equipped with similar partial encapsula tion to the latest 231kW (310hp) low-noise diesels, the four-valve-per-cylinder models will meet the forthcoming Austrian rules.
To get the required noise reduction Steyr has had to use special shielding round part of the engine, especially at the sides. Combustion has been quietened with softer injection characteristics using new fuel pump cams, and a reduction to 800bar injection pressures.
The air tanks have been fitted with blow-off valve silencers; the exhaust is a twosilencer system, and the exhaust brake also has a silencer.
The noise reduction package adds some 4-5% to the cost of a truck, and 50% of Austrian Steyr orders are now for the reduced noise trucks.
Driving the Steyr 19S31 fitted with the low-noise engine proved that decreasing the outside noise does not necessarily increase its in-cab levels. We found the truck was uncannily quiet, even when trying hard fully-laden up 6% inclines.
On the descent the exhaust brake proved to be well silenced.