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Last of the few

19th June 1982, Page 55
19th June 1982
Page 55
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Page 55, 19th June 1982 — Last of the few
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This man 16.280 with turbocharged engine is uncannily quiet, reports Tim Blakemore, and its thirteen-speed Fuller gearbox is a delight to use.

11-1IS ROAD TEST of the MAN 16.280 is the last in CM's current ;eries of six tests of tractive inits at 38 tonnes gcw with a tilt ;emi-trailer.

If Parliament ultimately ap)roves the White Paper propo;als on increased maximum veights, then 38 tonnes will be :ome the normal gcw for CM ests around the Scottish route Ind, judging by the operational rial results we have so far obained, that will soon enable us provide even more evidence hat vehicles do indeed operate nore efficiently at the higher veight. Parliament's attention has been turned elsewhere over the past two months, but this issue has certainly not been forgotten. The next stage in the proceedings is for the Government to publish draft amendments to the Construction and Use Regulations, and a vote will then have to be taken on these amendments.

The vote and the debate which is certain to precede it are not expected to take place before the• end of this month.

Considerable doubt still exists in many quarters whether the Government will receive the support it needs.

The results of this operational trial show how the MAN 16.280 'compares with five of its main rivals on the British market when operated at 38 tonnes gross. It is clear from the test results summary table that in a number of performance areas the 16.280 closely matched IVECO's 170.30.

On each of the four timed hill sections, for example, there was never more than 15 seconds difference in the recorded times. There is only 89kg difference in the two tractive units' kerb weights, measured at MIRA with the vehicles in ready-for-the

road condition, and the two vehicles' overall average speeds around CM's 1,184km (736 miles) Scottish test route were within 0.47km/h (0.29mph) of each other.

Both of these tractive units also were fitted with the same type of gearbox — Eaton's Fuller Roadranger RTO 9513, overdrive, twin countershaft model. However the overall gearing of the MAN (on 12-22.5 tyres) is very different from the IVECO (on 11-22.5 tyres) — 49.2km/h (30.58mph) per 1,000 revs in top gear for the MAN as .against 55.59km/h (34.55mph) per 1,000rpm in top for the IVECO.

It is this gearing that lets the big Fiat engine work at a low, economical speed (around 1,750rpm) at a road speed of 97km/h (60mph) whereas at motorway sped the relatively small (11.4-litre) MAN engine is spinning much faster, taking the rev counter needle out of the green "economy" zone to around 1,950rpm. This accounts in part at least, for the MAN's relatively poor fuel consumption results.

The MAN's overall average fuel consumption was the worst of the six vehicles tested in this series and it was the only one unable to better 7.0mpg over any of the motorway sections. But to put the results into perspective, it is worth pointing out that there was less than six per cent difference in fuel economy between the best (Volvo) and the worst (MAN) in the group.

The 27 6hp, turbocharged D2566 MTF is the odd engine out in this group test; it is not a despeeded high-torque variant. Its modest peak torque of 1,075Nm (7 9 3lbft) is developed at 1,500rpm and maximum power is developed at 2,200rpm, though the engine will run up to 2,300rpm before the maximum speed governor cuts in.

This engine is the blown version of the 240hp naturally aspirated unit fitted to the 16.240 FTN (CM road test July 4 '81). In that road test report I commented that the first thing any driver new to the vehicle is likely to notice is the quietness of the cab interior and soft tone of the engine. The turbocharged version is even more muted and the result is an uncanny hush in the cab, no matter how hard the engine is working.

As with the 16.240, the low noise levels are due almost entirely to the engine's combustion chamber design and not to any special cab insulation. MAN engines with the M type (mittelkugel) combustion chambers in the past have been described as "whisper engines". That might be taking poetic licence a little too far but if they do not actually whisper, they certainly speak very softly.

The maximum noise level I recorded in this 16.280 cab, and that at full throttle, pulling hard up Shop was 76dB(A). At a steady 60mph in top gear the noise meter was readin 74.5dB(A), at 50mph it read 7: 73dB(A) and at a steady 40mp the reading was 7 3.5dB(A These noise levels are so lo that when using overdriv on the top four gear ratios, th most prominent noise in the ca was the whine of the overdriNd gears.

This MAN engine then clearly one which cannot be di yen "by ear" and it is essential I take heed of the rev counter I obtain the best fuel econom. The instrument is commendab clearly marked and now that th instrument panel's angle to th vertical is greater than it used I be on earlier models, all the dia

are easy to read.

The tachometer's green eci nomy zone extends frol 1,300rpm to 1,900rpm and, whi the engine's peak torque is d veloped at 1,500rpm, I four that the engine pulled mo strongly at 1,600-1,700rpm. U less it was quite obvious that ti 280 was going to make it to top of an incline in one ge without a down change, the was nothing to be gained fro letting the engine speed fall 1,500rpm and below.

Provided the revs are kept u the 16.280 at 38 tonnes gross is a very different proposition, so far as journey times are concerned, from the 16.240 at 32.5 tonnes gross.

That vehicle was capable of reasonably respectable average speeds over the easiest sections of CM's route, but began to lag behind as the going got tougher. The 16.280 was never noticeably sluggish and its overall average speed at 38 tonnes gcw was some 2mph faster than the 16.240 at 32.5 tonnes gcw.

Seldom in CM's road test reports are major criticisms made of Fuller nine and 13-speed gearboxes, and this test is no exception. The RTO 9513's ratios are well suited to 38-tonne opera tion in this country and it matters little whether the engine driving the constant-mesh box is a low-speed Cummins or RollsRoyce, or a relatively high revving MAN unit.

On motorways, this 13-speed Fuller was a delight to use, beca use the engagement and disengagement of overdrive was so smooth and reliable and a change down to 12th gear (direct) was all that was needed for so many motorway gradients. In the 16.280, unless a driver is listening hard for a change in the tone of the gearbox whine, the only indication that a shift from 13th to 12th has been accomplished is that the rev counter needle holds steady or begins to climb, whereas previously it was falling.

Like the 16.240 tested last year, this MAN's suspension was the standard multi-leaf type but its ride quality was noticeably superior to that daycabbed model. This is not caused by any difference in wheelbase — MAN's sleeper and day-cabbed tractive units share the same wheelbase of 3.1m — but could well be because of the better weight distribution between the axles on the vehicle hauling 38 tonnes. MANVW took special care in fitting the fifth-wheel in the optimum position on the 16.280.

There was a marked similarity between this 16.280's park brake performance and a number of MAN tractive units previously tested by CM. They have all been poor. It would seem that British operators of MANs are expected to have to live with the fact that new vehicles only barely satisfy the requirements of Construction and Use Regulations.

In complete contrast, the service brake performance of the 16.280 was first class, with good peak deceleration, reasonably short braking distances and no hint of overbraking on the drive axle — a disturbing feature of a number of recently tested tractive units.

Summary Any operators who carefully examine the specification of the 16.280 are bound to be impressed by the amount of equipment which usually comes under the "optional extras" heading but which is fitted as standard by MAN. The list includes Kysor radiator shutter, SAB automatic slack adjusters, XZA tyres including spare wheel, tyre and carrier, radio!cassette player, exhaust brake and an unusually comprehensive kit of good quality tools.

Furthermore, the current retail chassis price of the 16.280 is unchanged since last October and MAN-VW at Swindon is not aware of any imminent price increase. Perhaps the intention is to hold the price until the introduction to Britain later this year of the 281 model.

This and the 321 model have been a long time in making their debut in this country. If their introduction coincides with confirmation that maximum weights are to be increased, operator interest in the new models is sure to be even greater.

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