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Graham IVlontgomerie tests the new Cummins-powered Seddon Atkinson and returns
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not only excellent economy but also the . . . .
Shortest ever round trip time
IN BRIEF
Price as tested: £20,620 Weight: 32.5 tonnes 132 tons) gcw Payload: 20.9 tonnes (20.6 tons) Overall fuel consumption: 36.214/100km (7.8mpg) Overall average speed: 73.2km/h (45.5mph) Power to weight ratio: 6.3kW /tonne (8.5bhp/ton)
THE FIRST CM test of a vehicle powered by the new Formula E290 Cummins engine was aimed to coincide with the power unit's official release on February 3. However, as regular readers will remember, the weather put an effective stop to that, with heavy snow affecting the whole of the northern part of the route. We have now repeated the test under more normal weather conditions so the results can be compared with those of other vehicles with no "ifs" or "buts".
The final test was a resounding success for both Seddon Atkinson and Cummins. Not only did the 400 Series record the shortest ever round-trip journey time, but it came within a whisker of achieving the best-ever fuel consumption! In fact it missed the latter by less than one gallon over the 700-odd miles of the CM Scottish route. It was, in fact, a test of "firsts" —the first time a 32-tonner has averaged more than 45mph for the whole test and the first time that the eight-hour barrier has been broken for the northbound stage.
Overall the 400/E290 recorded a splendid 36.21it/100km (7.8mpg) at an average speed of 73.2km/h (45.5mph).
Mechanical details
Our test vehicle was a sleeper cab version of the familiar Seddon Atkinson 400 series. The new Cummins engine— originally referred to as the "Big Cam"— is based on the familiar 14 litre (854cuin) design complete with its distinctive fuel injection system. The maximum power of 204kW (273bhp) is produced at 1,90Orpm with a recommended change-up point at 1,600rpm.
Although the nine-speed Fuller gearbox was "conventional" Seddon Atkinson, the axle choice was not. As with the Rolls-Royce 2651_, the Cummins needs a axle ratio higher than that available with the Seddon —Group" axle. Thus the test machine was fitted with an Eaton axle with a ratio of 4.56 to 1.
The first stage of the operational trial route from Hemel Hempstead to the Forton service area was covered in the shortest time ever—a hint of what was to come. This was achieved at a fuel consumption of 371it /100km (7.6mpg) which was excellent for this combined motorway/A-road section.
On the wholly motorway section up to Gretna, the long gearing of the Seddon Atkinson really paid off. At 60mph in top, the Cummins was turning at only 1,400rpm, with the result that the fuel consumption nudged the eight mpg mark while averaging 88km/h (54.7mph).
Apart from the superb overall result, the real eye-opener as far as I was concerned was the performance over the switch
back A68 section between Rochester and Neville's Cross. With the high gearing I had suspected that the 400 might prove tricky to drive here, in spite of the "let it lug to 1,000rpm" characteristic of the Cummins. The reason for repeating part of the test. Although the snow cleared gradually on the run south, the road conditions were still treacherous on the original test.
The shortest ever round-trip journey time was recorded. Nothing could have been urther from the truth. The Sedion Atkinson proved itself just 3s much at home on a succes;ion of 1 in 10 gradients as it lad been on the motorway. This vas again reflected in the fuel ;onsumption for this stage of 17.2Iit/ 100km (6.0rnpg). To )ut this in perspective, a result )f worse than four mpg is not mcommon for this part of the est.
On the hills, performance vas excellent, with the 400 resarting from rest on the 1 in 4 est hill at MIRA. The Carter Bar :limb on the Scotland /England )order was disposed of in 4min 37sec a very rapid time vithout going into the low range )f the Fuller box. We had an deal gearing for this particular lin in that fifth gear (or sixth if IOU count crawler as first) was Jsed at 1 ,60Orpm for almost he whole of the climb.
Well matched The Fuller and the Eaton axle were well matched to the torque :haracteristics of the latest from ihotts. As can be seen from the iccompanying gear change diagram, the individual gear ;pacings were well balanced, giving a useful over-the-road )erformance. The only criticism have of the overall gearing :oncerns the top speed.
With the 4.56 axle ratio, the ieddon Atkinson was geared for ibout 116km / h (72mph) in top vhich could make it open to ibuse With this new generation if low engine speed /high axle atio machines the way would ippear to be open for the effec ive use of a road speed goverior (or a tachograph?). Thus the nanufacturers could gear for !conomy without the associated iroblem of overspeeding Weak spots
The Cummins automotive ,ngines have had two weak pots in the past they were hirsty and noisy when :ompared with the majority of heir competitors. As far as the uel economy aspect goes, the esults of this test speak for hemselves. An overall fuel conumption figure of 36.2 lit/ 00km (7.8mph) at such a high verage speed is proof indeed of ow the Cummins engineers ave got their sums right.
Fuel consumption is a matter f facts Noise is very much a -latter of opinion, and on this oint I am not convinced that he Formula E290 is quieter -tan its predecessors. It has a fferent engine note I grant
you, but I did not notice an improvement. This, of course, is one of the problems facing vehicle engineers in this day and age in that what sounds quiet to the ear on a subjective basis may not show up as such on a noise meter. I have only one reservation concerning the engine and that is connected with the driving style. If the engine is driven as Cummins recommended then it is a very economical unit indeed but it is a big 'if'.
It worries me that so much is dependent on the individual driver keeping to the recommended rev range.
As tested the Seddon Atkinson/Formula E290 cost £20,535 El 9,500 basic, £165 for the axle option and £870 for the sleeper cab.