Detroit four-stroke
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by Tun Blakemore
PRE-PRODUCTION prototypes of Detroit Diesel-Allis o n 's new four stroke engines, the 60-Series, are expected to begin on-road trials M Europe in September.
Full production of the 11.1litre and 12.7-litre in-line sixcylinder engines is scheduled to begin in the USA, probably at either the Redford or Romulus, Michigan plant, in October, 1986.
Prototypes of the 11.1-litre engine are currently undergoing field trials in Texas, fitted to Freightliner tractive units.
The General Motors sub-. sidiary, which claims to be the largest diesel engine manufacturer in the USA, is already confident that its new engines will significantly boost its market share among truck manufacturers on both sides of the Atlantic.
The two-stroke V6 and eight cylinder 71 and 92Series engines for which Detroit Diesel is probably best known have only ever sold in very small numbers in Europe, largely because of poor fuel consumption.
Reliability problems have also dogged the 92-Series in the USA. Detroit Diesel-Allison's major goals with the 60-series engine are to set new standards of fuel economy and reliability.
The maximum power ratings of the 11.1 litre 60-series engines (bore/stroke, 130/139mm) range from 179 to 270kW (240 to 350hp), those of the 12.7 litre engine (bore/stroke 130/16 Omm) from 261 to 298kW (350 to 400hp).
Both engines are turbocharged and air-to-air chargecooled and have overhead camshafts and four valves per cylinder.
A 300hp (gross) 11.1 litre 60-series develops its maximum power at 1,800rpm and its maximum torque of 1,200 [bit at 1,200 rpm.
A particularly advanced feature of all 60-series engines is their electronically controlled fuel injection equipment, with unit injectors.
The GM division is also reckoned to be well advanced with the development of a low heat rejection, turbocompound version of the 12.7 litre 60-Series engine with valve scat inserts, valve guides and exhaust manifold made from a ceramic material. This will be rated at up to 500hp.