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Engine
 One of the most important keys to achieving top performance in a Super Sports motorcycle—and especially one like the Fireblade, intended for use on both street and track—is realising a stronger and more effective power-to-weight ratio. Increasing power alone only affects part of the total performance equation, as excessive vehicle weight can easily cancel out gains made in engine performance. From its first debut in 1992, the CBR900RR and CBR1000RR Fireblade’s engineering teams have rigorously focused on the overall balance of this equation by developing race-winning power in concert with intensive efforts to reduce the inertial weight that keeps a motorcycle from achieving its full potential. With each succeeding generation, the Fireblade’s development teams have found new ways to not only boost power output, but also radically reduce weight, resulting in impressive increases in its critical power-to-weight ratio, and by extension its overall performance. For 2008, the second generation of the CBR1000RR proves to be no exception. A complete redesign of its basic configuration realises not only stronger, more manageable power, but also lighter weight in the components that most affect the engine’s pickup and acceleration.
New Separate Sleeveless Cylinder Block
In order to achieve the stronger, higher-revving power output that the Fireblade’s engineering team was looking for, a larger bore and shorter stroke were called for. In order to keep engine size and weight down, this new configuration required replacement of the current model’s ceramic-composite cylinder sleeves with a highly rugged new JCP (Jet-flow Circulation Plating) cylinder wall surface treatment which permitted the cylinder bores to be increased from 75 to 76mm, reducing cylinder spacing from 6mm to 5mm while maintaining the same cylinder pitch and overall cylinder width as before. Effective cylinder weight was also reduced, making a significant contribution to the new engine’s overall 2.5kg weight loss compared to its predecessor.
New, More Compact Head Configuration
In line with its new sleeveless cylinder block, the Fireblade’s engine also features a newly designed, more compact head that is 15mm shorter and 9.5g lighter in weight than its previous configuration. This was achieved by shortening the lengths of the valves by as much as 3.5mm and relocating the camshafts 4mm lower and 4.5mm closer together. New, lighter-weight thin-wall camshafts also realise a remarkable 500g savings in weight while maintaining the same levels of strength and rigidity. For further weight saving and quicker, higher-revving performance, new titanium intake valves feature high strength to match their lighter weight, as well as lighter weight springs that precisely close the valves with less force and minimised high-rpm float.
Lighter, Larger-Bore Forged Pistons
Featuring a 1mm larger diameter, the Fireblade’s new forged aluminium pistons also remarkably maintain the same weight as the pistons they replace. Carefully redesigned to be both structurally stronger and effectively lighter, these new pistons combine with a 1.5mm shorter stroke to make an important contribution to the engine’s higher revs and faster pick-up and acceleration.
Newly Developed Assist Slipper Clutch
As all expert sportsbike riders and racers know, racing places enormous loads on a motorcycle’s drivetrain, and one of the most extreme is back torque caused by hard engine braking into corners. While engine braking through rapid downshifts is a highly effective way of more quickly reducing speed before entering a corner, under the extremes of racing the back torque or force of the faster spinning rear wheel on the slower engine can cause the engine to overrev or result in wheel hop as the wheel’s back force on the chain loads up the rear suspension and engine compression momentarily overcome the lightened rear wheel’s limits of traction. Either of these results can be unsettling distractions for a rider, robbing one of precious fractions of a second in lap times in the heat of competition.
In racing circles, one common solution to this problem has been the addition of a back torque-liming ‘slipper’ clutch, which releases the excessive reverse loads on the clutch by mechanically forcing it open slightly and disengaging or ‘slipping’ the clutch, thus allowing the rear wheel to more smoothly catch up to engine speed. Honda is well-versed in the use of slipper clutches, having first developed such a system for its revolutionary 1979 NR500 racer and then applying an updated version in its VFR Works Superbike racers in 1982. On production machines, the 1994 VFR750R (also known as the RV45) was also equipped with a slipper clutch. However, until now the Fireblade’s engineering team have not felt the need to adapt a slipper clutch to this production Super Sport’s engine. Partially, this was because it was felt that few non-racing riders needed or could even effectively take advantage of such a system, and also because the slipper clutch as it is currently known still has a few weak points that required resolution before Honda felt it could introduce such an addition on its production Super Sports models. Still, as other manufacturers have introduced this development on their higher performance models, calls have grown louder for a similar system on the CBR1000RR to meet the needs of racers and aggressive riders who strongly rely on engine braking to more quickly slow their speed into corners.
Much like the development of the Honda Electronic Steering Damper, Honda’s engineers weren’t satisfied with simply imitating what’s gone before, but instead set out to develop a vastly improved system that resolves inherent problems in the accepted design. In the case of conventional slipper clutches, one shortcoming is the amount of spring pressure required to force the clutch back together once the engine is again accelerating and no more slip is required. With some designs this can result in an unsettling momentary interval of ‘freewheeling’, with no feeling of connection between the rear wheel and the engine. With other designs counteractive measures can result in uncomfortably stiff clutch action or require repeated fine-tuning of spring pressure depending on riding or racing conditions. Honda’s engineers thus studied all the variations of slipper clutches to be found on the market, made some fundamental advances in design, and now feel confident that their new Honda Assist Slipper Clutch is fully ready for release installed in the new 2008 CBR1000RR Fireblade.
Like most slipper clutches, the Honda Assist Slipper Clutch utilises a set of tapered cams to separate and disengage the clutch pressure plates when strong downshifting back torque is fed to the clutch from the rear wheel. The force of regular deceleration from shutting the throttle generally does not introduce enough back torque to cause the mechanism to disengage the clutch. However, unlike most conventional slipper clutch designs, the new Honda Assist Slipper Clutch features another set of undercut cams to quickly force the pressure plates back together again and firmly reengage the clutch almost the instant engine power is reapplied. This design innovation thus minimises disengagement time while greatly reducing the amount of spring pressure needed to reengage the clutch. In fact, clutch spring tension is so light that the new Fireblade now uses conventional cable actuation instead of a hydraulic clutch to optimise lever feel.
Downshifting into corners aboard the new CBR1000RR Fireblade is now a smooth, unruffled affair, with a more natural feel as its new Assist Slipper clutch comes into play. However, besides the new system’s greatly enhanced braking performance and smoother control into and through the corners, its newly developed ‘assist’ mechanism assures both quicker and more assured clutch reengagement and much lighter and more comfortable clutch actuation in virtually all riding and racing conditions. Not only will this advanced new system reward expert riders and racers with smoother operation and faster lap times, it will also provide the vast majority of riders with smoother and quicker downshifts, lighter clutch feel and much more comfortable, less potentially distracting operation than may be experienced with other systems.
New Mass-Centralised Underslung Exhaust System
One of the most obvious changes to be seen in the new 2008 CBR1000RR Fireblade is its compact, mass-centralised exhaust system, which is now concentrated almost entirely underneath the engine. In the interests of quicker, more responsive handling, the CBR’s previous ‘Centre-Up’ exhaust system was moved from its high location extending back underneath the seat to a position as close as possible to the motorcycle’s centre of gravity, and directly under the engine, thereby minimising the inertial effects of the system’s weight and mass on the machine’s ability to quickly change directions.
Maximum cornering clearance was also a critical element in the design of the new exhaust, and the bulk of the stainless steel system fits within the small triangular area described by the of the lowest point in the centre of the undercowl and the two foot pegs, with nothing protruding that might touch the ground and interfere with the extreme cornering angles associated with racing at peak speeds and competitiveness.
The exhaust then exits out the two ports at the end of its large right-side secondary muffler, reaching up just below and behind the swingarm pivot. This complex secondary muffler has also been specially designed for optimum cornering clearance, rising well out of the area of contact when cornering hard to the right, and even the swingarm’s pressed aluminium right-side arm was formed in a new gull-wing shape to provide ample clearance for the new system.
The muffler also incorporates a pair of exhaust valves that maintain the engine’s full potential throughout its powerband while assuring complete environmental compatibility. Designed to maximise the engine’s exhilarating blast of high-speed performance, these electronically controlled valves also play a large part in the CBR’s remarkably smooth driveability.
Ultra-Low Exhaust Emissions
The new 2008 CBR1000RR Fireblade may be an aggressive Super Sports charger, but concern for the environment has always been a top priority in its ongoing development. Full conformity with Europe’s stringent EURO-3 emissions regulations is an obvious necessity, and this was accomplished, as always, with Honda’s proven HECS3 oxygen-sensing catalyser system, which monitors exhaust emissions and controls the intake’s air/fuel mixture to maintain optimum combustion efficiency and neutralisation of harmful exhaust gases at all engine speeds. However, the Fireblade’s ultra-low emissions were also achieved hand-in-hand with a significant boost in power and performance together with a major loss of weight, which other machines in this competitive class will have a hard time duplicating.
Chassis
For ultimate control on the streets and on the circuits, the CBR1000RR’s race-winning technology prominently features an innovative cast aluminium frame that helps centralise the motorcycle’s main components for lighter handling and quicker, smoother response to every rider input.
Offering an optimal balance of light weight and rigidity, this organically designed frame allows the machine to settle more securely into turns and change lines with assured ease, whatever the riding conditions or its rider’s level of expertise.
New Four-Piece Cast Aluminium Frame
In the quest for further reductions in weight and better centralised chassis mass in this next generation of the CBR1000RR Fireblade, the number of component parts used in the construction of its frame was reduced from nine pieces to only four main castings, achieving a weight reduction of nearly 2.5kg. The frame’s four sections include a large, new steering head casting with two large holes moulded in for ’Blade’s new straight-shot ram air ducts, the two intermediate side engine hanger rails, and a single large U-shaped rear pivot mount section that wraps under the rear of the engine to surround the swingarm pivot and further ensure the frame’s exceptionally rigid form. While all sections are hollow-formed with approximately the same wall thicknesses as the sections used in the construction of the current model, the new frame is significantly stronger than the unit it replaces—with lateral rigidity increased 13%, torsional rigidity up 40% and vertical rigidity up 30%—as well as being 30mm slimmer and more compact overall.
Without the previous CBR’s ‘Centre-Up’ exhaust system to support, and a much smaller tail cowl, the new frame’s cast aluminium seat rail could also be made shorter and lighter, for a small but important reduction in inertial weight. On top of this, the mass centralisation achieved with its new underslung exhaust system effectively reduced the CBR’s roll inertia by 13% and yaw inertia by 10%, for significantly quicker turn-in response that really must be experienced first-hand to be believed.
New Gull-Wing-Shape Hybrid Aluminium Swingarm
 As noted above, in order to provide clearance for the new underslung exhaust system’s large upswept muffler, the CBR’s strong and lightweight hybrid aluminium swingarm was redesigned with a new ‘gull-wing’ apex formed into its pressed aluminium right-side member. This new swingarm is 11mm longer than the one it replaces, with a 16mm longer set length that ensures smoother, more confident high-speed tracking while still maintaining essentially the same short wheelbase as its predecessor for exceptionally quick cornering response. The swingarm’s pivot point was also raised slightly, increasing the swingarm angle from 9.5° to 9.67° to provide an optimal match to the engine’s increased power output.
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