2021 CBR1000RR-R Is Honda’s Response To The Ducati V4 R

Will the new Fireblade SP change everything in World Superbike competition?

2021 Honda CBR1000RR-R Fireblade SP
First human outside the factory test team to ride the 2021 Honda CBR1000RR-R Fireblade SP at a racetrack? That honor appears to have gone to eight-time Grand Prix world champion Marc Márquez. Will we someday see the 26-year-old MotoGP star on a works RR-R at the Suzuka 8-Hours? Honda hasn't won the legendary Japanese endurance race since 2014.Honda

Long before hardware appears, a new model exists as a cloud of speculation, artists' conception drawings, and suggestive patent applications. For years, everyone was sure Honda would produce a V-4 MotoGP-replica super streetbike. After all, Honda won countless 1960s Grand Prix world championships with its four-cylinder racers and brought the CB750 inline-four to market in 1969, putting that romance within all motorcyclists' reach.

Years rolled by and, when it appeared in 2015, the replica V-4 was a fizzle—$184,000 for an emissions-compromised RC213V-S making disappointing power. It was packed with race technology and very beautiful, but it was not what the motorcycling world had dreamed of, an accessible super-high-tech production bike meeting EPA and CARB standards.

Here it is, the all-new—not warmed-over—CBR1000RR-R Fireblade SP with a 999cc inline-four, redlined at 14,500 rpm, and with MotoGP's bore and stroke of 81.0 x 48.5mm, which is very different from the current CBR1000RR's 76.0 x 55.0mm and the same as Ducati's V4 R. The shorter stroke reduces crankshaft diameter, allowing gearbox shafts to be located closer to it, making the engine shorter front to back. Because the starter now turns the clutch gear rather than a gear on the crank end, the engine becomes narrower. Changes to case wall thickness and shape increase rigidity.

Cam drive
In this drawing of the silent chain drive to the two camshafts, we see from the arrow at the bottom that the CBR1000RR-R engine rotates forward. A gear on the crankshaft drives the cam idle gear, which is in unit with a chain sprocket driving the cam chain. Note that the cam-chain tensioner is at the front because of reverse cam-chain rotation. You can see the very compact and nearly flat combustion chamber defined by the piston and narrow valve included angle. The intake camshaft is mounted higher than the exhaust to provide clearance for the steeply downdraft intake port.Honda

The anticipated greater stress of higher-rpm operation has redefined the valve train, eliminating 75 percent of the weight of traditional inverted-bucket tappets by switching to Formula 1-style finger followers. As in the Honda MotoGP V-4, this engine’s cam lobes are coated with ultra-hard DLC, enabling them to survive sliding friction at idle. When MotoGP began 17 years ago, engines were warmed up by throttle blipping, keeping cams spinning fast enough to generate full oil films between them and tappets. Then came a year when race engines warmed up at idle, just like streetbikes. That impressed me. Good stuff, DLC.

Because it’s rough on cam chains to wrap tightly at high revs around the usual half-size sprocket on the crank, this engine’s cam drive is a hybrid by gear from the crank to a slower-turning gear above, which carries a sprocket that drives the Morse chain from there to the two cams.

Bore and stroke of 81.0 x 48.5mm is very different from the previous 76.0 x 55.0mm and the same as Ducati’s V4 R.

The crankshaft has larger bearing journals, bucking a long trend to ever-smaller ones. The goal here is to challenge Kawasaki, the current World Superbike champion, and Ducati, whose V4 R won so many races in the early season, so mechanical reliability comes first. On four of those larger journals are titanium connecting rods and caps, joined by chromium molybdenum vanadium steel bolts, in all lighter by 50 percent than the alloy steel rods they replace.

Pistons are forged in A2618 aluminum alloy as in the 3V-S, which is what the engineers call the RC213V-S, and they are oil-cooled by a new system that serves two goals. Remember back when AMA Supersport privateers increased oil-pump internal clearance, claiming this saved power? For this same reason, some F1 and production-car engines have two-speed or variable-speed oil pumps, a high ratio for lower revs and a lower one for higher rpm, to prevent power loss from delivering too much oil. In this RR-R engine, Honda uses the piston-cooling oil system to achieve the same effect. At lower revs, when piston oil cooling is not needed, a spring-loaded ball valve closes, sending all the oil to bearings. As the engine revs up and oil pressure rises, the ball valve opens, delivering the excess oil being pumped to the piston cooling jets. Instead of providing a single jet to each piston, this system sprays in multiple directions to achieve more comprehensive piston cooling.

Honda camshafts
In this view of the valve train, the black DLC coating can be seen on all cam lobes. Finger followers pivot on two rocker-arm shafts. Each camshaft is supported by five plain bearings to minimize cam bending from the large forces required to lift and accelerate the valves at high rpm. Why not ball bearings, as in some earlier designs? Ball bearings are much less radially stiff than plain bearings and provide much less damping.Honda

Piston cooling by oil jet is essential to the modern sportbike because, without it, pistons would have to be made thicker-crowned and heavier to conduct combustion heat to the cylinder walls. That extra piston weight would increase vibration, inertia loads, and the power lost in bearing friction.

Piston skirts are coated with Ober’s Type 03 material, which combines two solid lubricants, black molybdenum disulfide and PTFE, to assure uneventful break-in and low-friction operation. Compression ratio, a prime element of engine torque and determinant of fuel economy, is a high 13:1.

Losses in the crank chamber are reduced, according to Honda, “by RC213V-S methods,” which to me implies that measures have been taken to prevent loss from the fast pumping of crankcase air from cylinder to cylinder as pistons rise and fall. In a V-4, this is done by giving each crankpin pair of cylinders its own crank chamber and scavenge oil pickup. In an inline-four, vents may be provided between cylinders to allow freer passage of moving air.

Cylinder operating temperature has been made more uniform, thereby improving piston-ring sealing by better maintaining cylinder roundness and lack of taper, by use of two sets of coolant passages, upper and lower.

engine cylinders
Normally the tops of engine cylinders are hotter than their lower parts because of their greater exposure to hot combustion gas. This can lead to bore distortion from heat expansion, possibly compromising the sealing of the pistons to their cylinders. To reduce this source of cylinder taper, a separate bottom water jacket and warmer coolant loop helps to equalize cylinder temperatures, top to bottom.Honda

The tilt of the intake-valve stems has been reduced to further flatten the combustion chambers, which became necessary when bore was increased from 76.0 to 81.0mm. Each time bore is increased and stroke shortened to reduce piston acceleration and stress at a given rpm, there is danger that combustion will become slower in a wider and vertically thinner combustion space; simply put, the tighter the chamber, the harder it is for charge motion to spread the flame. Honda has years of MotoGP experience with these 81.0 x 48.5mm dimensions, so all engineers are revealing to us is that slight reduction in the valve included angle. If there were a big problem, could Marc Márquez have won 11 races this year?

Those who have followed Superbike intake-port design since the days of the RC30 know that ports have become shorter and distance from throttle valve to intake valves has shrunk as well. In the CBR1000RR-R, port volume between the 52mm throttle butterflies and their valves has been reduced 13 percent.

Honda’s trend-setting 1983 VF750F Interceptor was intended as a homologation special just to legalize the use of advanced technologies in AMA Superbike racing. For that reason, only a small number—some say 1,200—were initially produced. But street riders loved the effects of those technologies on handling and engine responsiveness, creating strong market demand that Honda hadn’t anticipated. We are told that CBR1000RR-R production will be limited, but when a manufacturer designs new capabilities into such a bike, the chance exists that a multitude of riders will embrace them. Let’s see what happens as World Superbike machines become ever-more-similar to MotoGP prototypes.

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