AT THE HEART OF THE ROAD TRANSPORT INDUSTRY.

Call our Sales Team on 0208 912 2120

Relaxed power, choppy ride

13th March 1982, Page 49
13th March 1982
Page 49
Page 50
Page 51
Page 49, 13th March 1982 — Relaxed power, choppy ride
Close
Noticed an error?
If you've noticed an error in this article please click here to report it so we can fix it.

Which of the following most accurately describes the problem?

We test the same vehicle previously taken over the Scottish route at 32 tons: at this higher weight fuel consumption actually improved

HE LAST in our series of 38)nners is the very same IVECO 70F30T that I tested at a gcw of 2 tons in October, when WE0's new turbocharged range lade its debut in the UK.

The 300hp machine impressed le then with its uncommon bility to climb so many graients in either overdrive top or irect top gear (13th or 12th in le Fuller RTO 9513 box). At 38 )nnes gross, it was much the ame story. And this time the /ECO tractive unit was fitted iith the lower of the two availble axle ratios.

On the first day of this test, ,etween junction 12 on the M6 nd Burton Services, the hardest work I had to do with the gear3ver was flick the overdrive witch into "direct" on the few ills where the beefy 14-litre Fiat ngine could not put enough ractive effort at the rear wheels o pull overdrive. For the considirable climb past Keele Services sven that was unnecessary: vithout a murmur of complaint he IVECO tractive unit went )ver with the overdrive cog enpaged.

Despeeded, high torque enlines for heavyweights have low become the rule rather than the exception; all the vehicles tested here, for example, have engines of that general type. But in my opinion none, not even the NTE 370 Cummins with its massive power and torque, can match this Fiat's willingness to slog away at low engine speed in a high gear.

Paradoxically, this characteristic could be part of the reason for the IVECO's relatively slow average speeds. Knowing that the engine pulls so well low in its rev range, it becomes almost a point of honour for the driver not to change down until absolutely necessary when in fact a slightly earlier change may have resulted in a faster journey time.

Regular readers may wonder why our first fuel check point has been changed from Forton to Burton. Users of the former services, if they have ever had the misfortune to fill up with diesel there, will probably guess. For some time it has been obvious that the diesel pumps at Forton are in dire need of repair or rep! a ce m en t. Two seem constantly to be out of action and the remaining two look decidedly rickety. The film of spilled diesel fuel that always surrounds the pump islands does nothing to make the place more attractive.

We have been prepared to put up with these inconveniences in the interest of operational trial consistency. But what we cannot continue to accept are pumps which have no price display for fuel delivered, blanked off digital counters, no tenth or hundredth of gallon display, and attendants who insist on requesting that we fill up "to the nearest gallon, please guv'nor." We aim to have fuel fill-ups accurate to the nearest hundredth of a gallon.

I am surprised that the Rank organisation, which runs Forton service area, considers this a satisfactory way to supply fuel to its customers. The Granada-run Burton area is currently undergoing reconstruction but nevertheless is much better, with a level, clean forecourt, fast, accurate pumps and helpful staff.

A comparison of the fuel consumption results over this first stage shows haw important it is that the pumps be accurate. Of the three most powerful engines in the group, the thirstiest over this section, the Volvo, used only a thimbleful over a quarter gallon more than the most frugal, the IVECO. Over a 150-mile section which includes 32 miles of fairly hilly A-road that is an unusual parity, and gave some early indication of how close the final results were going to be.

Compare the IVECO's first two mpg figures on this test with those achieved during the same vehicle's 32-ton test and you could come to the startling conclusion that adding weight actually improves specific fuel economy. However, even the most ardent supporter of increased weights would have a job to substantiate that argument, though it is easy to show that higher gross weights will lead to a lower cost per tonne/mile.

There are three main reasons for the apparent anomaly. Firstly, the tilt semi-trailer that we used for these tests has a smaller frontal area than the Crane Fruehauf van that we usually use (and will continue to use) for 32-ton tests. It is only at speeds above 80km/h (50mph) that the effect of air resistance becomes significantly greater than roiling resistance, but it is clear that this difference is bound to have an effect on fuel consumption.

Secondly IVECO (UK) tells us that after the first test, because of the unexpectedly poor fuel consumption over A-road sections, the fuel injection pump was removed and its calibration checked, and it was found to be overfuelling between 700 and 1,200rpm. This time the pump was set correctly.

Thirdly, as I mentioned earlier, for this test the tractive unit was fitted with the lower of the two differential ratios available in the UK — 3.96:1. Our results suggest that for most operations on British roads at 32.5 or 38 tonnes, this ratio is preferable to the 4.26:1 alternative. At no time during this test did the IVECO unit feel overgeared, not even over the notorious A68 stage.

Generally, on the more severe gradients, compared with our 32-ton trip, one slot lower in the gearbox was needed each time. That is not to say that there was ever a hint of the 44-tonner being in difficulty. On the contrary, there were always at least two ratios in hand in the twin countershaft Fuller.

On MIRA's test hills the 170F30T made light work of moving off from rest on a 1 in 4 in crawler gear. A not-too-sensitive throttle pedal and a good positive park brake action with no release delay help enormously in making this manoeuvre.

At the time of this first successful 25 per cent gradient restart our photographer had not arrived and as he particularly wanted a picture of the IVECO on the hill we repeated the test.

This time the restart was not quite so smooth and as the clutch plate gripped and fed 977Ibft of torque suddenly into the transmission there was a disturbing bang. A glance underneath revealed that the propshaft had broken close to the rear axle.

I should make it clear that this kind of exercise on a 1-in-4 hill is certainly not likely to be an everyday occurrence for a vehicle in service. And this was not the first or only vehicle ever to come to grief on the test hills, as you see from this week's Bedford test.

On the other hand, at 38 tonnes gcw the tractor was working well within its design weight limit and so might reasonably be expected to withstand a certain amount of rough treatment. The simple explanation could be that this particular shaft had a flaw in it.

The unfortunate rider to this sad tale, adding insult to IVE CO's injury, is that our photographer never got his picture on the hill.

Lacking the instant driver appeal of the Volvo cab and not being as roomy as the Bedford sleeper, the twin-bunk cabin from Turin nevertheless provides a driver with a welllaid-out working environment. It gives the impression of being designed by people who understand a long-distance driver's important requirements such as being easily able to reach and operate all the controls and read the instrument panel.

Summary

Compared with the longwheel-base Bedford and the Volvo with its more sophisticated suspension package, the ride of the multi-leaf spring IVECO was positively choppy but none of the tested vehicles could better its low interiornoise level.

The soft tone of the Fiat engine's exhaust note, regardless of how hard it is working, adds to the overall impression it gives of always working at a relaxed pace. There is never the bark of the Cummins engine at maximum torque or what has now become the Volvo growl at its new low speed.

A few points of detail could be improved, such as the too-dim tachograph panel light, quarter light pillars that usually obscure the field of vision through the rear mirrors, door locks that seem to be definitely under-engineered and a wobbly exhaust brake button. However, these are only minor criticisms and they should be placed in perspective against this fine tractive unit, obviously capable of high productivity at 38 tonnes.

T.B.

Tags

Organisations: Rank, US Federal Reserve
Locations: Turin

comments powered by Disqus