Cummins' air attack
Page 14
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• The new 347kW (465hp) Super E465 diesel is the first model in Cummins' 14-litre range to feature air-to-air charge-cooling. Until now, the long-established charge-cooled in-line sixes, built in the US and at Cummins' Shotts plant in Scotland, have used enginejacket water to cool induction air leaving the turbocharger before it enters the engine.
The air-to-air charge-cooling system, a relative novelty for Cummins, was developed on this side of the Atlantic, mainly at the company's Darlington technical centre. The new NTAA-465, is not Cummins' most powerful 14-litre model ever — but it does produce the greatest output from a single turbocharger: in this case the latest BHT3B unit from Cummins' Huddersfieldbased Holset subsidiary. Injection pressures of up to L190 bar (17,500psi) are generated by a revised injector cam profile; a product of Cummins' "Big Cam" philosophy first expounded over a decade ago with the introduction of the original E290 engine. The new cam profile combines with a revised injector rocker arm ratio (reduced from 1.76 to 1.4) to speed up injection: fuel is now injected in only 350 of crank angle, compared with about 40° minimum on the E400.
These improvements to combustion efficiency have helped boost power output by 16%, but the 348kW (465bhp) is developed at 2,100rpm, against the E400's 1,900rpm. This, and a 15:1 compression ratio, compared with the E400's 14:1, raise engine stress levels.
To overcome any harmful effects of this increase, Cummins relies on its "step timing control" (SIC) system which amounts to a hydraulic tappet arrangement in each injector push-rod. Engine oil is used to extend the pushrod by about 5mm when the engine is working hard, retardating the injector opening to hold maximum cylinder pressures down to 133bar (1,950psi). This also aids cold starting.
To match the increase in power the E465 develops 1,770Nni (1,3051bft) of torque at 1,050rpm and 1,152Nm (850Ibft) at only 800rpm, compared with 868Nm (64011)10 from the E400, implying unproved hill-starting ability. Maximum torque is 1,938Nm (1,429Ibft) at 1,250rpm.
New components in the E465 include pistons, injectors, camshaft, cylinder heads (2), injector and valve push-rods, turbocharger, rocker levers and rocker cover. They will be shipped in from the US for engine assembly at Shotts.
ERF is expected to be the first chassis maker to offer Cummins' new air-to-air intercooled unit, which is also available in derated 306kW (410bhp) form.
Also officially announced by Cummins after its sneak preview by ERF at last October's NEC Motor Show is the NIA365 engine which shares the 465's revised cam injector and other top-end components. However, it does not feature STC and retains water-air charge-cooling. Rated at 272kW (365hp) (ISO) at 1,900rpm, it will eventually replace the established NTA-350 unit, with a claimed 2-3% improvement in fuel economy and enhanced torque.
Minimum specific fuel consumption of 194g/kW/hr at 1,500rpm is the best yet from a 14-litre Cummins. The company says the new 272kW engine is intended to provide a competitive match for trucks like MAN's 17.362, Leyland Daf s 95.350/350, MercedesBenz's 1735 and Scania's latest 113 — and it will be no more expensive in relation to its output than other current units.
Cummins' director of technical operations, Colin Brown, says the popular 10-litre range could be developed up to 261kW (350bhp), which is 19kW (25bhp) above the current air-to-air charge-cooled maximum. The L10 could be bored and stroked to about 1L3 litres, implying an eventual output capability close to 298kW (400bhp).
Cummins has not neglected its six-litre B and 8.3-litre Cseries truck diesels: their injection (conventional jerk pump) and turbocharger/charge -cooler systems have come in for attention. Air-air charge-cooling is now used for the first time in the B-series, in a new variant designated the 5.9-210 — the final figures indicate its ISO hp rating.
It sets a new claimed automotive diesel record for specific output, at 35.'7hp/litre, edging ahead of Mercedes' similarly-sized 0M366LA. Compared with the water-air charge-cooled B-series, best known in ERF's E6 17-tonner, output is up 16%, from 134 to 157kW (180 to 210hp). An inline Bosch MW replaces a rotary fuel-injection pump and is matched with revised injectors.