The New BMW R1200GS
Everything you ever wanted to know about the BMW R 1200 GS
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Modified cylinder heads and lighter valve drive.
Maintaining their basic design and configuration, the cylinder heads have also been modified. From outside they are recognisable by their different contours with striking cornered valve covers.
The principle of chain-driven camshafts below the valve plane and the operation of valves by means of tappets and rocker arms has been maintained. The reason, quite simply, is that this design concept has proven its qualities countless times – and although it is not necessarily designed and laid out for high speeds, the concept has confirmed its qualities and reliable function even under tough racing conditions in the BMW Motorrad BoxerCup. The big advantages of arranging the camshafts in this way are the economic use of space available (width of the cylinder head) and the ease of maintenance so important both in everyday use and on long journeys (adjustment of valve clearance).
Valve diameter is up by 2 mm or 0.79´´ (intake 36.35 mm/1.43´´ versus the former 34 mm/1.34´´, outlet 31 mm/1.22´´ versus 29 mm/1.14´´). To ensure better and more efficient dissipation of heat, the outlet valves are filled with sodium. Valve duct design has been modified to match the larger valve diameters and the duct contours have been improved in their dynamic flow conditions. In conjunction with the increase in engine capacity, these modifications contribute to the 18 per cent increase in engine output 101 hp and torque85 lb-ft. As the final result of this design improvement using the most advanced, computer-aided methods, weight of the cylinder heads has been reduced by 15 per cent.
Internal oil cooling of the cylinder heads already featured on the former engine has been adjusted to the higher level of output and torque by improving flow conditions and avoiding any kind of throttle effect. Oil cooling improves the dissipation of heat from the valve rim and ensures a more consistent distribution of temperature within the cylinder head. All this contributes to the engine’s robust thermal stability and helps to ensure the high standard of reliability so typical of a BMW. And these are definitely the criteria that count when travelling full of luggage to all four corners of the globe under the most difficult conditions.
New engine management now featuring two oxygen sensors, modified dual ignition and knock control.
The new R 1200 GS further improves the leading position BMW Motorrad has had for years in the area of electronic engine management. The Digital Motor Electronics code-named BMS-K (BMW Engine Management System) is an in-house development tailored specifically to the requirements of a motorcycle. Fully sequential fuel injection, integrated knock control, faster processing of complex sensor signals by means of the most advanced microelectronics, compact layout and low weight are the most important features worth mentioning in this context.
The principle of indirect air volume monitoring and control by means of the throttle butterfly angle and engine speed (alpha-n control) carried over from BMW’s existing motorcycles has been further enhanced on the R 1200 GS, creating a concept referred to as torque-based engine management.
The basic parameters determining the optimum engine operation point remain engine speed and the throttle butterfly angle monitored by a separate potentiometer on each cylinder. Applying additional engine and ambient parameters (such as engine temperature, air temperature, and air pressure), engine management, together with control maps and correction functions contained within the system, tailors the injection volume and ignition timing exactly to the engine’s and rider’s current requirements. Taking so many factors into account, the system is able to control torque with supreme accuracy, adjusting engine running conditions perfectly to all relevant parameters.
Fuel is injected into the intake duct exactly as required and exactly on time for the intake cycle of the respective cylinder (fully sequential fuel injection). With one oxygen sensor being allocated to each cylinder, fuel/air composition is controlled individually in each cylinder according to current requirements. Both oxygen sensors are arranged close to the engine in the respective exhaust manifold, thus ensuring individual and even more precise emission management. Whenever necessary, the fuel/air mixture may be adjusted much faster than before, naturally with individual control and adjustment of each cylinder.
The positive results of this process are exemplary emission management, greater fuel economy, improved riding conditions, and an even finer response to the rider’s commands. Or, to put it in a nutshell, even greater environmental compatibility together with enhanced sheer riding pleasure.
BMS-K also incorporates all the functions of automatic idle speed control as well as cold start enrichment with warm-up control. An appropriate increase in idle speed while warming up is ensured automatically and exactly on demand by so-called “idle speed steppers” (controlled bypass ducts for additional air) integrated in the throttle butterfly manifolds, together with a corresponding adjustment of the fuel injected.
Featured in all BMW Boxers (with the exception of the 850-cc power units) since 2003, dual ignition has been further modified and improved in the R 1200 GS. The auxiliary spark plug is now arranged at the outer edge of the cylinder, the ignition timing of both plugs being freely programmable and possibly varying in time as a function of load and engine speed in order to further optimise running smoothness, emission management, and fuel economy. Referred to as phase shift, this adjustment process is maintained consistently all the way from part load to full load.
In practice this means different ignition timing points on both spark plugs in defined control map areas: When approaching full load where dual ignition no longer provides any benefits, the phase shift effect is so large that the spark crosses over on the auxiliary plug in the expansion cycle (60° aTDC). For all practical purposes this corresponds to single ignition on the central spark plug under full load.
The BMW R 1200 GS introduces a new system of knock control never seen before with these features in a motorcycle engine. Knock combustion is recognised by a solid body sound sensor matched specifically to the cylinders. Receiving the appropriate signals, the electronic engine management will take back the ignition angle (i.e., it retards the angle) and protect the engine from possible damage. Engine temperatures are also taken into account in evaluating the signals, helping to supplement the safety function.
Benefitting from knock control, the geometric combustion ratio on the engine has been increased to 11.0:1, certainly a remarkable figure for an air/oil-cooled engine with cylinders of this size. Specific fuel consumption benefits accordingly, the R 1200 GS being almost 8 per cent more fuel-efficient than its predecessor in the EU2 test cycle.
Designed for unleaded premium fuel (RON 95), the engine, thanks to knock control, is able to run also on regular fuel (RON 91) or other fuel qualities sometimes to be found in various countries, without requiring any kind of manual intervention or adjustment. Within the limits available, knock control adjusts the ignition angle automatically to the fuel on which the engine is running.
Interacting with a wide range of sensors, knock control adjusts to even the most extreme conditions and requirements, for example with the engine having to withstand extremely high temperatures and thermal exposure in desert areas. To provide this reliability, the electronic engine management adjusts engine running parameters and thus ensures supreme reliability under all conceivable operating conditions.
Intake manifold – larger volume for an optimum cylinder charge.
Numerous calculations and examinations of the entire cylinder charge process, taking the intake manifold into account, were required in order to achieve an optimum charge cycle throughout a wide range of engine speed. Increasing the capacity of the airbox to almost 9 litres, BMW’s engineers have made the very best out of the geometric conditions dictated by the machine and the specific position of the manifold, naturally taking all ergonomic requirements into account.
To filter the intake air, the R 1200 GS uses the paper filter system already very effective in the R 1150 GS. In designing and configuring the shape of the intake funnel, the responsible engineers have succeeded in creating perfect harmony of flow conditions, on the one hand, and acoustic requirements (level of intake noise), on the other.
Exhaust system – efficient sound engineering for low noise with a throaty chortle.
The exhaust system is made up of two manifolds, a pre-silencer with catalytic converter, and a tailpipe muffler. The entire system all the way to the pre-silencer fitted beneath the gearbox is a twin-chamber configuration made consistently of stainless steel. Weighing exactly 10.7 kg or 23.6 lb overall, the emission system is approximately 33 per cent lighter than on the former model.
Flowing through the two single manifolds, exhaust gas merges in a Y-shaped unit combining the two flow processes and continuing straight into the pre-silencer housing the central catalytic converter. An interference tube close to the engine between the two manifolds provides the appropriate balance of pressure and helps to boost engine torque at low and medium speeds. With cell density of 200 cell units/square inch, the metal-based catalytic converter comes with a rhodium/palladium coating combining high temperature resistance with a long service life.
Introducing an all-new tailpipe muffler, BMW Motorrad has succeeded in creating an ideal match of smooth torque, low noise and a pleasant sound pattern. The interior structure of the muffler is based on the reflection principle, an inner sleeve with absorption material serving additionally to dampen high frequencies.
The muffler is oval in shape not only for optical reasons, but also to minimise the transmission of noise for even smoother and more pleasant riding conditions. A further special feature is the pressure-controlled valve integrated in the muffler and controlling exhaust gas counter-pressure for an additional reduction of noise under the engine’s primary running conditions, that is at medium to low engine speeds, thus keeping engine noise at a low level both objectively and subjectively, while at the same time giving the rider that “throaty” chortle he – or she – appreciates so much.
Both alternator and starter lighter than before.
Apart from the mechanical components in the engine, the electrical ancillary units also help to reduce weight to a minimum. To begin with, the R 1200 GS features a newly developed lightweight alternator with maximum power of 600 W. The layshaft starter has also been optimised for lower weight, and just like the battery it is absolutely free of maintenance requirements. In all, the total weight saving on the electronic components is 2.2 kg or 4.9 lb, that is 17 per cent lighter than before.
New six-speed manual gearbox with helical gears.
The R 1200 GS retains the proven principle of separating the gearbox from the engine – and at the same time the six-speed manual gearbox is an all-new development with features significantly improved once again over the previous version. Weight has been reduced to approximately 13 kg or 28.7 lb and for the first time BMW is using high-strength helical gears with smoother and more gentle gear mesh ensuring low noise and a high standard of refinement.
All gear increments are designed for active riding behaviour, meaning that sixth gear is not an overdrive or economy gear, but rather has an appropriately “short” transmission ratio.
The gear shafts run in anti-friction ball bearings, the gears themselves in low-friction needle bearings. The ball bearings come in clean bearing mounts sealed at the surface to keep out even the finest particles. This allows even longer maintenance intervals and reduces the cost of service, with only one oil change required in the gearbox every 40,000 km or 25,000 miles.
The gears themselves are shifted by means of a shift roller, shift forks and shift sleeves (as opposed to shift gears used in the past) to ensure smooth positive engagement of the gears. Made of aluminium, the hollow shift roller runs on ball bearings. Detailed improvements to optimise friction on the shift box, the shift shaft and forks improves gearshift operation once again and guarantees accurate, safe mesh on all gears.
Lightweight driveshaft and Paralever swinging arm – an innovative rendition of a traditional principle.
An absolutely indispensable feature of the new R 1200 GS like on all BMW Boxers is the traditional, maintenance-free driveshaft extending to the rear wheel. Having proven its merits for more than 80 years, this is the only logical drive concept with the crankshaft in longitudinal arrangement. And in practice this concept means supreme customer benefits, considering that chain drive, despite many improvements over the years, is not quite appropriate, given the need to regularly tighten the chain and the short lubrication intervals, for a large-capacity, high-power touring enduro.
Over the years BMW has consistently improved the driveshaft principle, meeting new requirements and demands in the process. The biggest innovation came in 1988 with the introduction of the Paralever swinging arm on the most powerful enduro at the time, the BMW R 100 GS: Using an additional pivot between the final drive and the swinging arm, BMW’s engineers were able to disconnect the unavoidable reaction of the driveshaft from the swinging arm, thus eliminating the often-criticised “elevator effect” with the rear end moving up and down when accelerating and applying the brakes.
A further advantage provided by the Paralever is that the springs do not harden when accelerating all-out, providing a significant improvement of traction as an important feature when driving up steep gradients on very rough terrain.
Considering these significant benefits, the higher weight and the increase in unsprung masses with a driveshaft versus chain drive are insignificant.
Still, in the process of developing the R 1200 GS BMW’s engineers did not stop until even this feature of the system more noticeable with an enduro used offroad than on the road, had ultimately been properly improved. Accordingly, the entire drivetrain of the new R 1200 GS has been redesigned all the way to the rear wheel and all features have been optimised. The result is a drivetrain which, together with the much stiffer Paralever swinging arm, reduces weight by approximately 10 per cent. Unsprung masses are down accordingly, ensuring an even more sensitive response than before on the rear wheel suspension already acknowledged for it superior qualities.
The main components of this new system are the axle drive and the swinging arm itself. Made of an ultra-strong cast aluminium alloy, the Paralever swinging arm, through its design and specific dimensions tailored to load conditions, is even lighter than before but also stiffer and stronger.
The geometric configuration of the entire swinging arm has likewise been modified, dive compensation is now almost 100 per cent. With forces acting on the final drive housing now being supported above the swinging arm, ground clearance at this point is greater than before, efficiently protecting the swinging arm even on very rough terrain against damage caused by rocks or similar objects.
The swinging arm itself is a two-piece forged aluminium unit. Another new feature is the re-configuration of the swinging arm mount moved from the final drive to the rear frame again in the interest of extra strength and robustness under the most extreme offroad conditions.
The pivot point of the axle drive unit resting in the swinging arm has been moved down to provide a more favourable geometric arrangement with greater stiffness. The bearing point, in turn, has been reinforced to match the higher load and forces from the more powerful engine.
With its improved kinematics, the driveshaft no longer changes in length as a result of geometric conditions. This also helps to save weight, since the length adjustment unit formerly fitted is no longer required. The shaft itself now comes as one single piece and – like before – runs without oil in the shaft sleeve.
The final drive housing is matched in its size and dimensions precisely to the inner contours of the angle transmission, avoiding even the slightest waste of space.
The crown wheel has been re-calculated and is also lighter than before, the wheel flange now being made of aluminium in order to save weight. With its larger diameter, the flange offers the wheel better support, with additional weight-saving potentials for the rear wheel around the hub.
The outer sign of distinction and a visual highlight of this extremely compact and elegant lightweight structure is the 50-mm hole drilled through the axle pipe of the final drive housing. The final drive itself comes with a lifetime oil filling, meaning that there is no need to change the final drive fluid throughout the entire running life of the motorcycle.
In re-configuring the design principles of the entire machine, assembly of the final drive has been simplified and further refinements introduced: The hollow axle sleeve helps to dissipate heat from the final drive through its large surface and efficient flow effects. Signals for the ABS brake system and the speedometer are read by a sensor directly in front of segment pieces on the crown wheel, making the outer emitter wheel used on the former model superfluous on the new machine.
Increasing the diameter of the drill holes on the wheel flange, BMW’s engineers are able to use five light wheel bolts measuring 10 mm in diameter and with longer expansion length instead of the former relatively heavy wheel bolts with a cone. This means even greater safety once again in bolting on the wheels and allows use of a smaller wheel bolt wrench (which means less weight in the toolkit).
New running gear – stiff, high-strength steel tube frame.
The R 1200 GS retains the basic configuration of all Boxer suspension concepts with the engine/transmission unit serving as a load-bearing element and the wheel guidance components being bolted on to the frame. The Telelever longitudinal arm, in turn, pivots on the engine housing, as before. The actual frame of the R 1200 GS is made up of the front subframe supporting the Telelever at the top and the rear frame with its integrated swinging arm mount.
The engine/gearbox unit is bolted on to the rear frame at five and on to the front frame at four points. Together, this composite structure incorporating the drive unit forms the motorcycle’s load-bearing framework.
The two frame elements of the R 1200 GS are lightweight structures in what is called truss design: The front frame is a triangular structure made up of high-strength steel tubes welded to one another. It offers the great advantage of highly robust support on offroad terrain plus package benefits over the former cast aluminium front frame as well as greater stiffness with weight remaining unchanged.
The rear subframe is also made up of straight steel tubes welded to one another. Precise calculation of all tubes serves to optimise both tube diameter and wall strength to exactly the right requirements, creating an overall configuration of maximum stiffness and strength on low weight. New features are the special mounts for the side-stand and main stand as well as the driver’s footrests connected directly to the rear subframe. The side-stand, incidentally, folds in easily and conveniently even when the rider is already sitting on his machine.
Refined Telelever ensuring even greater stiffness.
To this day, no other system of front wheel guidance and support is able to match the first-class functions and qualities of the BMW Telelever introduced in 1993 on the four-valve Boxers. The revolutionary principle of the Telelever using a wishbone to relieve the telescopic arm of longitudinal and lateral forces ensures unprecedented, highly sensitive front-wheel response on all road surfaces, together with tracking stability never seen before. The big advantages of this design concept are therefore supreme riding precision and accurate response combined with equally supreme suspension comfort and anti-dive control.
Refinement and modification of the front wheel geometry now further improves the qualities of the Telelever on the R 1200 GS over the former model. The longitudinal arm is an all-new, extra-strong and light forged aluminium component. In the interest of superior handling, front wheel camber has been reduced by 5 mm or 0.20´´ to 110 mm (4.33´´), the steering head angle remaining at 62.9° in standard position. A change in front wheel kinematics eliminates brake dive to an insignificant residual effect actually desired to give the rider the right feeling. The superior stiffness of the Telelever, in turn, has been further enhanced by once again increasing the diameter of the support tube from 35 mm (1.38´´) to 41 mm (1.61´´), thus making a further contribution to the crisp and clear riding behaviour of the R 1200 GS.
An important detail is the holes drilled into the lower fork bridge efficiently distributing brake pressure to the steel flex brake hoses for the right and left brake callipers without requiring an additional distributor unit.
Featuring fully encapsulated ball joints with permanent lubrication and with a lifetime oil filling in the telescope, the entire Telelever is absolutely maintenance-free.
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