Steyr's Monoblock Engines Making Waves in US Marine Market by PMarsh
The Austrian engine builder
Steyr Motors set up a North American subsidiary in 2006 to market its line of lightweight, high performance diesel
engines with a power range from 55 kW/75 hp to 184 kW/250 hp. Steyr was formerly part of the Steyr-Daimler-Puch group and became independent after its 1990 break-up. (Other spin-offs buildSteyr small arms and Steyr tractors.) The name comes from the town of Steyr in Austria, which is a major engineering and manufacturing center.
Engine production at the new Steyr Motorentechnik GmbH is based on the four-stroke "monoblock" diesel design that the company had pioneered in the early 1920s, coupled with modern electronically-controlled fuel injection. The range is based on inline four-cylinder and six-cylinder cores with two valves per cylinder and displacements of 2.13 L and 3.2 L. The displacement
per cylinder is 533 cc with a bore of 85 mm, stroke of 94 mm, and compression
ration of 18:1. Turbo-charging and charge-air cooling
Steyr did not invent the monoblock, but was the pioneer in applying it to diesels. The concept
was first applied to high-performance gas engines for aircraft and automobiles as early as 1909, when the French Delage was fitted with a 1.4 L version. One of the first "mass-produced" automobiles to use a monoblock gas engine was the V-8 Oldsmobile Viking 1929-30, followed by the Ford V-8 monoblock in 1932. However, the extra cost was not justified for mass-production of cars at a time when gas was cheap
and there was no incentive to remove weight from a vehicle.
Steyr has successfully refined its version of the monoblock into a package that delivers power-to-weight ratios close to those of gasoline engines, while maintaining the diesel's reliability
and torque. Essentially, the monoblock is an iron-alloy one-piece casting containing the entire overhead valve train, combustion chamber and cylinder in one compact unit with removable crankshaft bearing supports. By eliminating the head
bolts and head gasket
, the monoblock can be cast with larger and more functional coolant
passages, improving heat distribution and greatly reducing deformation and stress in the cylinder head.
This superior coolant
path and double-circuit cooling
allows the engine to handle maximum speeds of up to 4500 rpm
and be rated for continuous duty at 2800 rpm
. To handle this level of performance, all elements of the combustion system are high quality: the dynamically-balanced crankshaft is forged chrome-molybdenum steel
and the pistons are high-silicone aluminum
pan is a separate aluminum
two-piece casting that is clamped to the lower half of the monoblock by through-bolts at both ends. The pan carries all the attachments and is insulated from the monoblock by a heavy gasket
and flexible seals
around the crankshaft bearings. This significantly reduces noise
The engine's patented fuel-injection system is also notable: a lift
pump delivers fuel to a port on the end of the block, where it flows internally to the unit injectors. These are mechanically driven by the overhead camshaft and pressurize the fuel to 2000 bar/28,000 psi. The timing is controlled by a mechanical rack inside the valve cover that is computer /electronically controlled to produce a two-stage injection. This hybrid system features automatic bleed capability and as much as 80% of the fuel is returned to the pump. It allows the engine to meet EPA Tier 2 and can be by-passed in the event of an electronic failure, permitting the use of the default mechanical setting.
Building on the experience gained with the 170 kW/230 hp Steyr 236, the company's engineers initiated a re-design to increase power output. The engine management, injection timing, camshaft-housing and cover as well as piston & piston rings were all upgraded. With a Holset waste-gate turbo-charger, the new model was designated the Steyr 256-developing 184 kW/250 hp. This engine weighs 708 lbs, has a horsepower to weight ratio of 2.73:1. It has the same footprint as a GM small block V-8 and the makers claim it is "the lightest, most compact and most dynamic alternative to gasoline engines."
Optional on all models is Steyr's integrated flywheel generator
, which extends the length of the bell housing by 30 mm. The three-phase brushless design uses a permanent magnet with 80% efficiency. The voltage options are 14V or 28V. The system is virtually maintenance
free and features a programmable electronic controller and CAN communicaton with engine management.
The Steyr's reliability
, fuel economy and high power-density have made it popular with military-vehicle builders throughout Europe/NATO for small tanks
, jeeps and personnel carriers. (A standard S 2000 Peacekeeper was listed in the Guinness Book of Records as the world's fastest tank at an average speed of 82.23 kph / 51.10 mph. It is powered by a Steyr 2133 that revs to 5,000 RPM and produces 200 BHP and up to 480 Nm Torque.) Steyr engines are used in commercial
vehicles built by Russian and Asian companies.
Steyr has also paid particular attention to the engineering of the marine
version, which is in worldwide use on fast rescue
boats, small patrol craft and sport-fishing boats, The company offers a unique package approach: it will modify the basic engine in the factory so that is ready to bolt straight on to whatever outdrive or waterjets the customer specifies. For sailing yachts, 75-85 hp Steyr engines can be packaged with the SD 10 Saildrive
from ZF Marine-which also has plant in Steyr. This creates a competitive marine diesel power package as an alternative to gasoline engines. Owners report the fuel consumption
is excellent at 3 gph per engine and represent a realistic alternative to the typical V-8 big block gas engines.
For 2008, the engine remains the same, but the heat exchangers and piping on top of the block have been re-designed for greater efficiency and given a more integrated contemporary look. The engineers have also capitalized on their experience with the flywheel generator
system by adding an entirely new hybrid power option. The hybrid transmission
contains an internal electric
motor/generator that will allow the engine to efficiently direct-charge a battery
bank and then run directly off electric
power at 600 amp/hours giving quiet low-speed cruising for a weekend.