Lightweight diesels on parade

A joint venture between MTU Friedrichshafen and Detroit Diesel has resulted in a new family of diesels intended for military applications, with half the size and weight of existing engines of the same power.

The high-power density 890 series is a completely new range of military engines intended for a new generation of armoured vehicles weighing between 10 and 60 tonnes.

Modular design allows configurations from four cylinders in line, up to a V12 to cover the power range 300-1000kW (400-1500bhp). Four and six-cylinder variants, the 4L and 6V, were shown at this month’s AUSA exhibition at Fort Lauderdale, Florida, and are being developed as candidates to power the US Army’s Future CombatSystems (FCS) manned ground vehicle. A V10 version has been chosen to power the German infantry’s Puma fighting vehicle.

Both the FCS vehicle and the Puma are designed to be light enough to transport by air, while still having a high level of armour protection. They are also designed to be highly mobile, flexible and fast. The FCS will weigh about 20 tonnes and the Puma 30 tonnes.

The four cylinder 4L 890 is only 455mm wide and can be front or rear mounted. It is designed to accept a flywheel generator for diesel-electric hybrid applications.

Running at up to 4,250rpm – twice as fast as a normal truck engine – it produces 410kW and 922N/m of torque. Its power-to- weight ratio is said to be twice that of other modern diesels of similar output and is said to be 30 per cent better than a typical car diesel.

The engines use the latest technology including third generation common rail injection. The new injectors have their own fuel reservoirs or accumulators containing sufficient fuel for one combustion cycle. According to the companies, this avoids interference between the injectors which can occur when a common reservoir is used, as is normal. The system operates at up to 1,800bar, and the electromagnetic injectors permit multiple injections in any one cycle.

The high pressure turbocharger, designed by MTU, operates at up to 4.5bar compared with a more usual 2-3bar and has variable geometry to achieve high boost pressure even at low engine speeds.Pumps, filters and the oil system are integrated within the crankcase instead of being mounted on the outside, helping to make the engine smaller, lighter and more rigid.

Both Detroit Diesel and MTU are part of DaimlerChrysler’s Off Highway business unit. Detroit Diesel is the biggest supplier of diesels to the US Army.

The manned ground vehicle, one of a range of FCS vehicles, is being designed by a consortium led by General Dynamics Land Systems and United Defence Partnership under a contract let by system integrator Boeing/SAIC, and is due to enter service in 2008.

The Puma is being developed by Rheinmetall Landsysteme and Krauss-Maffei Wegmann. It is due to be in service by 2007, and 410 have been ordered by 2012.

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