AN trumpets 'Silent' runners
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• Two new "Silent" trucks, an unusual mid-engined tractive unit, an air-injection system to reduce exhaust emissions and a clutch-less gearchange system are just some of the examples of new technology which German truck builder MAN will be displaying at next month's Frankfurt show.
Following the recent launch of its "Silent" G90 light middleweight rigid, MAN has extended its programme of downrating and encapsulating specific truck diesel engines to provide low-noise alternatives.
The 17-tonne M90 rigid is now offered with a de-speeded and encapsulated "Silent" version of the normal 6.8-litre sixcylinder D0826 engine. The low-noise, charge-cooled engine's maximum revs have been reduced from 2,600rpm to 2,200rpm with maximum power dropping from the normal 172kW (230hp) to 162kW (217hp).
Similarly, there is also a lownoise F90 tractive unit, based on the 19.362, again with a despeeded, fully-ventilated, encapsulated engine which pushes out 253kW (339hp) at 1,900rpm, as opposed to the 269kW (360hp) developed by the standard 11.9-litre engine at 2,200rpm.
By reducing engine revs, modifying the combustion process, and shrouding the engines with noise-absorbent cladding, MAN has reduced EC drive-by noise levels on its "Silent" G90, M90 and F90 models by up to 8dB(A).
The "Silent" trucks have been developed to meet forthcoming European noise regulations, and in particular to satisfy planned control on night-time truck driving due to be introduced by the Austrian government.
According to MAN, the three encapsulated low-noise engines "will be integrated into the production process in the autumn of 1989", and will cost on average between £1,600 and £2,200 extra.
Further "Silent" engine variants are expected to be developed by the company for sale in the spring of 1990, although, for the moment, MAN-VW, has yet to say whether it will be offering the low-noise engines as an option in the UK.
As part of its continuing programme into reducing exhaust emissions, MAN has been looking at ways of cutting down on particulates without having to rely heavily on cumbersome filter systems. At Frankfurt next month it will exhibit an unusual air-injection system on a turbocharged 6.87-litre underfloor bus engine which significantly reduces particulate emissions during the engine start-up and moving off phase when black smoke is more of a problem.
Under the system, at the beginning of the acceleration phase, compressed air, provided by a storage tank fed by the normal brake compressor, is injected into the inlet manifold aft of the turbocharger.
This sudden burst of air, together with an increased fuel injection rate, leads to considerably higher initial torque and acceleration, along with more efficient combustions thereby improving initial exhaust gas quality. Air injection is controlled electronically in the moving-off range, and is shut off as the engine's turbocharger comes into normal action. MAN intends to fit the airinjection system initially to citybuses, where the control of exhaust emissions is more critical. It says that a charge-cooled engine fitted with the airinjection system is an "up-todate alternative to the naturally-aspirated engine with a particulate filter" (A more complete description of the MAN air-injection system will be featured in a forthcoming Engineers' Notebook) in CM.
Taking pride of place on the MAN stand at Frankfurt, however, is likely to be its UXT concept tractive unit which features a mid-mounted, underfloor engine and air disc brakes on the front axle — MAN says that it is "quite conceivable" that air discs could become available on the front axle of its trucks during 1991.
The 19.362 UXT's engine is fitted with the flywheel at the front with a modified propshaft taking the drive back to the rear axle via a flange drive.
While admitting that the UXT's driveline layout is complicated, MAN maintains that the design offers a number of significant advantages over a conventional tractor — not least in increased vehicle stability, better driver ride comfort and load distribution, plus the potential for easily adapting tf vehicle to four-wheel-drive an the opportunity to produce a tractor with a wheelbase as short as 3,100mm.
Along with its unusual driveline, the UXT tractor wil also be fitted with a newlydeveloped high-roof F90 cab, although MAN says that this will not become available until the start of 1991 at least.
Following on from its use o the semiand fully-automated versions of Eaton's Twin Split ter gearbox, MAN is also developing a clutchless gearshift based on the automatic dry clutch system developed by Fichte! arid Sachs.
An electronic control box automatically disengages and engages the clutch on each gear change made by the driv er: at a recent press preview of its Frankfurt show exhibits MAN demonstrated two 17tonne rigids fitted with the automated dry clutch, or ATE linked to an Eaton Twin Splitter box and ZF Ecosplit synchromesh transmission.
MAN claims that the ATK system not only reduces the amount of work the driver has to do, allowing him to concentrate more on steering and braking, but also it reduces drivetrain wear and the risk oi transmission damage through faulty handling.
MAN has added a number c new rigid models to its range in time for Frankfurt, includir4 the 14.262 with an underfloor, horizontal version of the 10litre five-cylinder engine currently offered in the UK in thc 17.262 tractor.
The 14.262 features a hydrostatically-driven fan with a radiator in the same position as a that in a conventional F9C
Other products out in time for the show include weightsaving composite springs and an aerodynamic wind deflector package for the F90 tractor which includes an adjustable roof spoiler, side deflectors an chassis-mounted fairings. 0 A full description of all the latest technical advances in thc European truck industry will b featured in our Frankfurt Shov report in Commercial Motor 21-27 September.