From Ducati's press material:
The Multistrada - 1000cc Dual Spark Engine
The essential design goal
Technically, the "1000 DS" is an all-new 90 L-Twin power plant. The design starts with completely new cylinder heads and further innovations that extend to the very heart of the motor, the crankshaft. The design goal was clear. Increase total power, boost mid-range power, simplify mechanicals, lower engine temperatures, raise reliability, lower emissions and lighten weight.
The Ducati air cooled engine
The 90-degree Desmo L-Twin, fuel-injected, two-valve, air-cooled engine is most well-known and widely used power plant in the Ducati family of motorcycles. Although the Desmoquattro and Testastretta L-Twin liquid-cooled engines power all of our Superbike family and selected models within the Monster and Sport Touring families, the air-cooled L-Twin is just as important to our philosophy of motorcycling. An air-cooled engine has significant design and application advantages in many motorcycles. The most obvious is the relative simplicity and lighter weight of an air-cooled motorcycle verses its liquid-cooled counterpart. There are no radiators, water pumps, hoses, venting tubes, reservoirs, or the need to compromise the placement of ancillary components displaced by the liquid cooling system. The straightforward, no-nonsense approach is in itself an attraction for many. Maintenance on an air-cooled engine is also simplified and therefore the long-term cost of ownership is lower. Of course, to many the beauty of an air-cooled engine, with its traditional cooling fins and purposeful look, is as an important factor as any. "It makes my bike look like a 'real' motorcycle," people say.
The 90-degree L-Twin philosophy
With more experience and success with twin-cylinder performance engines than any other manufacturer in the modern era, Ducati has brought the design to a high art form. The Ducati commitment to the L-Twin design is based on our conviction that its configuration is a sound engineering approach to powering a motorcycle. Compact, efficient and powerful, the twin-cylinder motor has endured as the common-sense means to power a motorcycle since the first powered two-wheelers appeared more than 100 years ago. Confirmation of the twin's continuing validity is the ongoing dominance in the World Superbike Championship of motorcycles powered by a twin-cylinder engine, no matter who the manufacturer is - a point of fact not lost on our worthy competitors, as more and more attempt to switch to the twin-cylinder design.
As others try to "catch-up," Ducati continues to lead the way. Desmodromic valve actuation, Testastretta design, fuel injection, computer engine management, CAN line electronics and now the new "1000 DS" engine just keep pushing Ducati farther ahead of the pack.
Starting with the cylinder heads, ignition is now accomplished with two spark plugs per cylinder and the conventional method of supporting the camshafts with ball bearings has been replaced with oil pressurized plain bearings.
The "Dual Spark" design, due to its "double flame front" offers more complete combustion, increased power especially in the mid-range and greater fuel economy. The advantages of the use of plain bearings to the Desmodromic motor are many, including a reduction in the number of moving parts, which increases reliability and reduces weight. In fact, the result is an amazing reduction of more than 1.5 kg/ (3 lbs). per cylinder. Additionally, the new approach reduces heat and improves heat dispersion.
A reduction in valve-angle degrees between the intake and exhaust has created a more "compact" head. The more compact design has many advantages. It allows a more optimal shape to the combustion chamber resulting in more complete fuel combustion, higher compression and more power. The new more efficient combustion chamber allows the use of quite "lean" fuel/air mixture without damaging high temperatures and significantly reduced Hydrocarbon emissions. The new configuration also places the camshafts in a more direct relationship to the valves, lowering friction and stress to valve components and consequently increasing reliability. Although more compact, the new head gives more "room" for the valves. With the combined benefits of the new cylinder heads, Ducati engineers can now be more "radical" in valve size and cam design compared to the previous air-cooled engines. Intake and exhaust valves are now increased to 45 mm vs. 43 mm and 40 mm vs. 38 mm, respectively. The new valves are lighter, due to the smaller 7 mm stems (the same as our Superbike engines), even though the working diameter of the valves has increased.
Further improvements include new valve seats made of beryllium bronze, an advanced material previously used only on racing engines. The new valve seats have improved heat dispersion and low wear characteristics, thus valve clearance is maintained more accurately over time. The bigger valves are matched to new camshafts. Additionally, the cylinder head is now sealed to the cylinder via a special metal gasket. The gasket improves sealing, increases heat transfer, eliminates o-ring seals and simplifies assembly.
Complimenting the new valve layout are larger intake and exhaust ports. Additionally, the exhaust port length has been shortened by an incredible 40%, further aiding in the reduction of engine temperatures by exiting exhaust gases from the cylinder head more quickly.
The manufacturing process of casting the cylinder head is also new. It is now "gravity chilled" with the combustion chamber facing down. As a result, the first aluminium poured forms the combustion chamber and cools first, and quickly, ensuring better molecular structure (smaller aluminium grains) of the combustion chamber.
Another design criteria was to have the engine make power over a wider range. In addition to the new cylinder head, contributing significantly to power output is not just a bigger bore, but also longer piston stroke. To ensure broad mid-range power, the crankshaft, cylinder bore and piston have been modified to achieve a 94 mm bore with a 71.5 mm piston stroke, vs. the former 92 mm x 68 mm of the 900 cc engine. The pistons now feature nitrided steel rings with a high sealing ability that essentially eliminates oil consumption.
The cylinder barrel is now thicker making it more rigid and more resistant to deformities while tightening down the cylinder resulting in improved piston and ring-to-cylinder sealing. Two extensions (fins) have been added to the lower cylinder to support the piston better at BDC (bottom dead center).
Lower engine temperatures and reliability have been enhanced with a new shape, placement and a greater number of cooling fins. The new shape, essentially an exaggerated pyramid, has a greater mass (greater heat sink qualities) at the source of heat (combustion chamber and cylinder liner) to conduct heat away from source more quickly. The fins then grow gradually thinner (lighter) as they extend away from the heat source while maintaining the same surface area (the ability to transfer heat to the atmosphere).
Crankshaft and Connecting rods
The new 94 mm pistons are linked to the crankshaft with new connecting rods, made from a new material composition, 30NiCrMo4, which has exceptional flow characteristics during forging. This allows Ducati engineers to design a more optimal shape to the connecting rod cross-section because of the consistent and flaw-free characteristics of the new material during the forging process. In cross-section, the new rod is thinner side-to-side, but wider fore-to-aft; a more advanced I-beam, which is stronger and lighter for increased reliability and performance. Additionally the rods have been mechanically and chemically surface stress relieved resulting in a smoother and imperfection free surface for higher reliability and strength.
A new forged crankshaft was also called for. Its of a new shape, with its mass more centralized, and oil delivery ports are positioned in a new way, through less structurally critical areas. The result is a crankshaft that is more rigid and has less flex, lowering vibration and increasing reliability.
The timing belt gears now have 20 teeth verses the former 18 teeth, which improves routing and reduces stress to the belt. Crankshaft and camshaft timing gear mounting has also been improved and simplified, ensuring rapid and accurate assembly.
The lubrication system has also been updated. The 1000 DS runs significantly higher oil pressure and volume, achieved with the use of a new oil pump and oil channels. The higher oil pressure is required by the plain bearing camshaft, but also aids significantly in engine cooling and reliability.
The clutch basket, drive plates and driven plates have been improved and updated. Both the basket and plates are now made of special aluminium. The service life of the new lighter clutch is much greater, due to the more balanced wear factor of aluminium alloy to the friction plates. The clutch is also quieter due to improved tolerances and the lower resonance of aluminium vs. steel.
The transmission output shaft (layshaft or countershaft) has been improved with the use of a double row bearing on the chain sprocket side for improved durability and strength. Furthermore, the countershaft sprocket is now mounted on the splined counter shaft via a single large nut, verses the former two screws for improved reliabilty.
New top to bottom, the fuel-injected Dual Spark Desmo 1000 L-Twin engine achieves new power, efficiency and reliability - and is the perfect match for the lightweight and aggressive Ducati Multistrada 1000 DS.