4L 890 Inline Diesel Engine: The Latest Technology for FCS

• Small Size - High Power up to 550 hp (410 kW)
• Commonality with Vee engines
• State of the Art Technologies
• Technical Data: Comparison 4L and 6V 890

Ft. Lauderdale - The 4L 890 diesel engine was presented for the first time at the AUSA Exhibition in Ft. Lauderdale. The engine is not derived from a commercial application diesel, but is being developed within the 890 family of engines especially for military applications. The Detroit based Detroit Diesel Corporation and mtu, located in Germany, have jointly proposed this new High Power Density Series of engines for the FCS manned Ground Vehicle. Both are companies of the DaimlerChrysler group and experienced in producing and selling military engines to military customers around the world.

High Power Density up to 550 hp (410 kW)

The 4L 890 engine has two power output versions, 350 kW and 410 kW, and can be front or sponson mounted in military vehicles. The 4-inline cylinder engine is only 17.9 inches (455 mm) wide and can fit into very confined and narrow engine compartments.

It is by far the lightest diesel of that power and meets the FCS programs engine weight threshold. In addition, overall propulsion system weight reduction potential is achievable by using the 4L 890 engine. The engine was designed to accept a directly mounted compact electric flywheel generator with a weight of only 135 kg.

The 4L 890 runs at maximum 4250 rpm, double the speed of truck engines. The mean effective pressure, with many diesel engines no higher than 20 bar, reaches 26 bar for the Series 890. All of the specific diesel engine criteria, i.e. mean effective pressure, average piston speed, charge air pressure ratio, specific load on bearings and others are in the same range or lower than realized in the 880 AAAV engines. Producing 410 kW with the 4L 890 leads exactly to an engine load for which the engine series was designed and compares to a 6V 890 engine operated at 550 kW.

Synergies with Vee engines

The new 4L 890 has a high commonality of parts with the existing 6V 890, which is a result of the family concept of these engines. Those parts, which are different, depend on the number of cylinders. All other components are primarily identical. This makes the logistical support for the engines very easy when different versions of the engine family are used for different vehicles. The number of spare parts and tools can thus be reduced as well as the time necessary for training.

State of the Art Technologies

Like the existing 6V 890 engine, the 4L is a new design. Many parts which are usually mounted on the outside of the engine - pumps, filters and oil system - are now integrated into the crankcase. This makes the engine smaller, lighter and more rigid. The technologies employed are a third generation common rail injection system, a high pressure turbocharger system with variable nozzle geometry and a state-of-the art electronic engine management system. In contrast to truck-derived diesels, which are usually low speed, the engines speed of 4250 rpm facilitates the integration into a hybrid drive system package. The valve gear train is hydraulically adjusted and therefore needs no maintenance. The cooling system is split into a low and a high temperature circuit. The high-temperature circuit provides cooling to the core engine i.e. liners, cylinder heads, etc., and the first stage of the charge-air cooler. The low-temperature circuit cools the starter-generator power electronics, the second stage of the charge-air cooler in addition to the engine's oil. This concept reduces radiator size and allows coolant temperatures of up to 130 degrees C (266 degrees F) downstream of the engine.

The Common Rail injection system of the Series 890 has very successfully been employed on mtu's Series 880 tank engines as well as on the company's commercial engine series 4000 and 8000. Up to now, DaimlerChrysler Off-Highway has sold more than 7000 engines with this system. The Common Rail injection employed on the Series 890 engines builds up pressures of 1800 bar, a prerequisite for efficient combustion resulting in low fuel consumption and low emissions.

The electronic engine management CDS (Control and Diagnostics System) has been developed and manufactured by mtu as an integral part of the engine. CDS contains the controlling, governing and monitoring functions for the engine. A diagnostic function of the electronics explains when, why and how a failure occurred, an optional prognostic function provides information about the expected future status of the engine and its components.

The turbochargers of the Series 890 - like those of many other mtu engine series, have been specially developed and are manufactured by mtu. With flexible turbine geometry, the torque is raised at low engine speeds improving fuel consumption. At part load, the fins inside the inlet part of the turbine partially close and push more pressurized air into the combustion system.

Technical Data: Comparison 4L and 6V 890

	4L 890	6V 890
Number of Cylinders	4 inline	6 / 90 degree Vee
Bore	4.52 inches	4.29 inches
Stroke	4.21 inches	4.21 inches
Displacement per cylinder	1.11 liter	1 liter
Power at rated speed, maximum	560 hp at 4250 rpm	750 hp at 4250 rpm
Torque, maximum	922 Nm at 4250 rpm	1235 Nm at 4250 rpm
Injection system	Common Rail	Common Rail
Max. Injection pressure	1800 bar /26.125 psi	1800 bar /26.125 psi
Oil system	Dry sump	Dry sump
Dimensions (height x width x length)	790 x 455 x 1255 mm	590 x 700 x 760 mm