Honda’s CBR1000RR is trailing the rest of the superbike field when it comes to brute power these days but the firm’s latest patent applications suggest that won’t be the case for long. The firm—which pioneered variable valve timing and lift in its cars—is planning to apply the same thinking to its range-topping sportbike.
Variable valve timing has been around for a while; Ducati’s DVT Multistrada and Diavel models use a hydraulic cam-phasing system, and Kawasaki’s 1400GTR has done the same for more than a decade, while Suzuki’s GSX-R1000 has a unique all-mechanical VVT setup, but variable valve lift is still a novelty on two wheels. Only BMW’s 2019 R1250 range and its new S1000RR superbike can offer the technology thanks to the firm’s new ShiftCam system. Honda’s Hyper VTEC—used on the VFR800F Interceptor and VFR800X Crossrunner and the Japanese-market CB400—might carry the evocative “VTEC” initials but in reality it’s a simple valve deactivation device, dating back to the mid-’80s REV system, rather than a true VVT setup.
Like the true VTEC system that’s been a feature of many Honda cars since the late 1980s, the new superbike variable valve timing and lift design is based on the idea of having two sets of cam lobes. Each valve has a “mild” lobe, to be used at low revs and tuned for torque, low emissions, and good fuel economy, and a “wild” lobe used at high engine speeds to provide maximum power. However, the new Honda patent applications show a setup that’s more like BMW’s ShiftCam than the traditional VTEC car system.
Like ShiftCam, the new Honda design features multi-part camshafts. There’s a splined inner shaft, while the cam lobes themselves are mounted on outer sleeves that can slide along that inner section. By shifting the sleeves from side to side, the different lobes are brought to bear on the finger followers above the valves.
The Honda design differs from the BMW system in small but significant details. Most notably, Honda’s patents show that its engine will use the cam shifting system on both the intake and exhaust sides, whereas BMW only alters the timing and lift of the intake valves. Secondly, Honda’s design provides separate camshaft sleeve sections for each cylinder, whereas BMW’s 2019 S1000RR uses only two outer sleeves, each dealing with two cylinders. Since the sleeves can only be moved to change between cam lobes when the valves are closed, the Honda design has a bigger window of opportunity to make the switchover.
The other notable difference is the method by which the outer camshaft sections are moved. Both BMW and Honda achieve the movement by pushing retractable pins into a spiral groove in each sleeve, so the camshaft’s rotation pulls the sleeves into the desired position. BMW uses solenoids acting directly on those pins to push them into the correct groove—a simple but slightly bulky way of doing it. Honda’s design uses sliding lateral shafts, which double as the pivot for the finger followers. Slid from side to side using oil pressure released by solenoids, these shafts have shaped slots that release or retract sprung pins into the spiral grooves on the camshaft sleeves. It’s an elegant solution, and a compact one that means the engine is no bulkier than a conventional design, but it adds to the parts count and complexity of the Honda system.
Why Do We Need VVT?
Although the internal combustion engine might be entering its twilight years, the challenge from electric power isn’t ready to replace it just yet. That means there are still future generations of gasoline motor to come, which will need to meet ever-tougher emissions restrictions. For most bike manufacturers, there’s a strong focus now on meeting the standards set to be introduced in Europe by the Euro 5 emissions standards. Unless delayed, they’re expected to come into force in 2021.
With them, we can expect a rapid increase in the number of bikes using variable valve timing or variable valve timing and lift systems as manufacturers attempt to reduce exhaust emissions without cutting peak power levels.
High-revving superbikes are the machines that will struggle most to meet emissions limits. That’s because, in order to make lots of top-end power, they need plenty of valve overlap. That’s the brief period at the end of the exhaust stroke and the start of the intake stroke when both the intake and exhaust valves are open simultaneously. Although you need overlap to efficiently fill the cylinder with fresh intake charge at high engine speeds, at low revs that overlap period is longer than necessary, potentially allowing unburned fuel into the exhaust and damaging emission results and economy.
Variable valve timing is the clearest solution to the problem, and one that’s become commonplace on cars over the last 30 years. Cam-phasing is the most common solution, using a device between the cam sprocket and the camshaft itself to rotate the camshaft by a few degrees in relation to the sprocket, advancing or retarding the timing as desired. However, systems like VTEC and BMW’s ShiftCam also alter the valve lift (how far each valve is opened) and duration (how long the valve is open for) to get even greater benefits. Smaller valve openings at low revs can boost torque, while opening the valves wider and for longer at high revs increases gas flow for maximum power.
What Else Do We Know About Honda’s Next Superbike?
Talk of an all-new CBR1000RR has been rampant for years, since the basic components of the current model can still be traced back to the 2008 machine, but these patent applications are the first clear indication of technology that the next Honda superbike is likely to use.
Another big clue to an upcoming change comes from the fact that in last October Honda finally gained trademark rights to use the “Fireblade” name in the USA. Ever since the original CBR900RR was launched in 1992, the model has been known as FireBlade (later losing the capital “B” to become Fireblade) elsewhere in the world, while the States has stuck to the less evocative alpha-numeric nomenclature. Now, with Honda gaining rights to use “Fireblade” on “motorcycles and motorcycle structural parts” in the US, it looks like we’re also going to officially adopt the title over here.
It’s pure speculation at this stage, but could Honda be planning the name change because “CBR1000RR” will no longer be a suitable title for the next-generation bike? We’ve already seen Ducati’s Panigale V4 and Aprilia’s RSV4 moving to 1,100cc, and the Fireblade legend was built on the idea of bucking traditional capacity classes when it was originally launched as an 893cc bike into a sea of 750cc opposition.
The idea of an oversize, 1,100cc Fireblade could be further strengthened if the endless rumors of a 1,000cc V-4 Honda superbike ever turn into a reality. With WSBK regulations now encouraging homologation specials with limited production runs, and Honda already having developed a road-legal version of the V-4 RC213V MotoGP engine for the uber-expensive RC213V-S streetbike, the planets appear to be aligning for such a machine. Bear in mind that the original 1992 Fireblade started life as a rejected 750cc proposal; Honda went instead with the V-4 RC30 and RC45 models as its race-oriented machines, in turn allowing the ’Blade to reach its full potential with an oversize engine. It’s hard to imagine many complaints if history repeated itself in this instance.