HONDA The Power of Dreams

Cylinder layout and V-angle

■2002 NV5A to 2006 NV5HD and NV5HG: V5 engine, V-angle 75.5°

With a change in the top class of the Road Racing World Championship to MotoGP, Honda developed its new RC211V racing machine, which it debuted in the opening round of the 2002 season and the first year of MotoGP. Although a two-stroke engine was also an option, it chose to build a four-stroke engine with displacement of 990cc, which was the largest possible under the regulations.

At the time, regulations specified a correlation between the number of engine cylinders and minimum machine weight, with 3-cylinder engines or smaller set at 135 kg, 4- and 5-cylinder engines at 145 kg, and 6-cylinder engines and larger at 155 kg. While more cylinders facilitate higher engine output, weight also increases. Honda’s deliberations focused on power-to-weight ratio, engine-generated vibrations, engine size and mountability, and equal roll, pitch, and yaw moments of inertia. As a result, it decided on a 5-cylinder V engine for its first RC211V model (type NV5A) and maintained this same cylinder layout through to its final RC211V model, the NV5HG in 2006.

The maximum engine displacement for MotoGP machines was kept at 990cc from 2002 to 2006 (changing to 800cc from 2007). Over these five years, Honda had many opportunities to dramatically change the engine type for its RC211V, but it chose to keep the same V5 engine that satisfied the above requirements. The good thing about V5 engines is that they are theoretically not subject to primary vibration (vibration at the frequency of crankshaft rotation) or coupling vibration (vibration between cylinders due to different crank pin angles), which means they do not require a balancer. This, and the fact that the extra cylinder, compared to a 4-cylinder engine, made it easier to achieve higher output, were particularly important reasons behind Honda’s decision.

In terms of the V-angle (angle between the two cylinder banks in a V-type engine), Honda maintained an angle of 75.5° for all of its V5 engines. Assuming a V-angle smaller than 90° would allow it to create a more compact engine, it settled on this figure as it enabled the combined force of cylinders—with cylinders #1 (front bank left side) and #2 (rear bank left side), and cylinders #4 (rear bank right side) and #5 (front bank right side), sharing the same crank pins—to be canceled by cylinder #3 (front bank middle).

Firing order and ignition timing

■2002 NV5A to 2006 NV5HD and NV5HG (irregular interval ignition): Cylinder #2 – (75.5°) – Cylinder #5 – (104.5°) – Cylinder #3 – (180°) – Cylinder #4 – (75.5°) – Cylinder #1 – (284.5°) – Back to Cylinder #2
■2004 NV5C Spec 3 (irregular interval, two cylinder simultaneous ignition): Cylinders #2 & #4 – (180°) – Cylinder #3 – (255.5°) – Cylinders #1 & #5 – (284.5°) – Back to Cylinders #2 & #4

One element that has a significant impact on engine output characteristics is the ignition timing of each cylinder. Honda adopted an irregular interval pattern for its RC211V V5 engine to make the engine as linear and user-friendly as possible in relation to throttle operation by the rider. With some exceptions, it kept the same firing order and ignition timing for every machine from the first model (NV5A in 2002) to the last (NV5HG in 2006).

One of those exceptions was the NV5C Spec 3 engine, which Honda introduced from the middle of the 2004 season. On this engine, it used an irregular interval, two cylinder simultaneous ignition known as “Big-Bang” timing. A major reason that the NSR500 two-stroke GP500 racer was the most powerful machine in the 500cc class during the 1990s was this irregular interval, two cylinder simultaneous ignition. This philosophy was carried over to the four-stroke RC211V NV5C MotoGP racer as well. Although successful, Big-Bang timing was slightly inferior in terms of output at high rpms. And because of the outstanding ease of handling of the RC211V’s original irregular interval ignition, Honda returned to that pattern from the NV5D model in 2005.

Bore and stroke

■2002 NV5A to 2003 NV5B: Bore 73.0 mm, stroke 47.3 mm
■2004 NV5C to 2006 NV5HD and NV5HG: Bore 75.0 mm, stroke 44.8 mm

Honda’s overwhelming strength enabled it to dominate the 2002 and 2003 seasons of the MotoGP, but rivals with higher top speeds that were faster than the RC211V in a straight line appeared from 2003. In response, Honda started to use a short stroke on its 2004 NV5C model engine. The aim was obviously to achieve high engine output through a higher revving engine, but the bore and stroke combination used on the NV5C ended up being used until the NV5HG, the final RC211V model in 2006.

NV5A engine (2002)

Cylinder design

■2002 NV5A to 2006 NV5HD: Front bank cylinder bore pitch 85 mm and rear bank cylinder bore pitch 68 mm ×2, front/rear bank cylinder offset 17 mm, Nikasil plated cylinders
■2006 NV5HG: Front bank cylinder bore pitch 80 mm and rear bank cylinder bore pitch 64 mm ×2, front/rear bank cylinder offset 16 mm, Nikasil plated cylinders

The RC211V V5 engine cylinders were uniformly laid out around cylinder #3 in the middle of the front bank. Cylinder bore pitch and cylinder offset (or more accurately the cylinder #1 and #2 connecting rod phase) also remained unchanged over the five models from NV5A in 2002 to NV5HD in 2006.

The only model that was significantly different was the NV5HG in 2006, a model with engine and chassis newly designed to further reduce the moments of inertia for the entire machine. Continuing the 75.5° V-angle V5 layout, Honda made the engine more compact in a thorough review of every detail. This included a considerable reduction in cylinder bore pitch and a reduction of around 6% for the front-to-rear bank cylinder offset.

Successive generations of RC211V engines used an integrally-cast cylinder block. When plating cylinders in the integrated cylinder block, masking tape had to be applied to areas that did not require plating. This took a lot of man-hours and made it unsuitable for mass production engines. However, RC211V engine production was low volume, so Honda just continued plating the cylinders in its integrated cylinder blocks. From the 1980s, it used a Nikasil plating technology for its motorcycle racing engine cylinders.

NV5HG cylinder block (2006)

Shaft configuration, crankshaft rotation direction, and distance between shafts

■2002 NV5A to 2006 NV5HD and NV5HG: Three shafts, forward rotation

Successive generations of RC211V V5 engines employed a three shaft configuration; crankshaft, main shaft, and countershaft. The crankshaft, and countershaft with a driven sprocket mounted on its left end, both are attached to the split surface of the crankcase. In V-type engines, the main shaft was positioned below and between the crankshaft and countershaft.

In such three-shaft systems, the crankshaft naturally rotates in the forward direction (in the same direction that the wheels rotate). The established practice in the MotoGP as of 2024 is to employ a counter-rotating crankshaft to increase front load and suppress the tendency toward wheelies. That effect was not sufficiently understood during the RC211V era, so Honda continued to use the minimum configuration of three shafts.

For the five models from NV5A in 2002 to NV5HD in 2006, Honda maintained the same distances between the three shafts. However, the distance between the crankshaft and countershaft was reduced by 27.32 mm for the 2006 NV5HG as part of a downsizing aimed at reducing the moments of inertia. Although the distances between the crankshaft and main shaft, and between the main shaft and the countershaft, had already been designed to be as small as possible, Honda still managed to reduce these distances by 1.5 mm each. (Crankshaft to main shaft distance was reduced from 116.0 mm to 114.5 mm and main shaft to countershaft distance was reduced from 65.5 mm to 64.0 mm.) The main shaft position was also lowered by 20 mm in the NV5HG to achieve a lower center of gravity, increasing the height difference against the countershaft from 30 mm to 50 mm.

Pistons and piston rings

■2002 NV5A: Piston weight 147.0 g, piston ring weight 9.7 g (3 rings)
■2003 NV5B: Piston weight 151.0 g, piston ring weight 8.5 g (3 rings)
■2004 NV5C: Piston weight 142.8 g, piston ring weight 4.9 g (2 rings)
■2005 NV5D: Piston weight 127.3 g, piston ring weight 4.9 g (2 rings)
■2006 NV5HD: Piston weight 127.3 g, piston ring weight 4.9 g (2 rings)
■2006 NV5HG: Piston weight 122.4 g, piston ring weight 4.9 g (2 rings)

The RC211V engine used standard combustion chambers with four intake/exhaust valves, with absolutely nothing out of the ordinary. The piston skirt surfaces were shot-peened with molybdenum disulfide to form the lubrication layer.

Honda modified the shape of its combustion chambers for the NV5B model in 2003. This engine used the same three piston rings as the NV5A in 2002, but they weighed 1.2 g less due to changes to the top ring and elsewhere. For the NV5C in 2004, the engine stroke was reduced and the pistons were shortened accordingly, which resulted in the pistons themselves being at least 5% lighter. The number of piston rings was reduced to two as well.

The choice of using two piston rings was aimed at reducing friction. At the time, Honda Racing Corporation (HRC) had very little recent experience using two rings, so the developers had to acquire their own knowledge through trial and error, including adjusting the shape of the piston’s second land (external volume) and the clearance between the inside surface of the top ring and the bottom surface of the ring groove.

The pistons themselves were changed considerably for the NV5D in 2005. With ribs added to the back surface of the pistons to enable thickness to be reduced, Honda was able to achieve light and highly rigid pistons, commonly called “bridged slipper pistons.” While this type of piston is a standard technology for MotoGP engines these days, Honda started developing its bridged slipper pistons in 2004, with their first use in a racing machine being on the NV5D model.

NV5HG pistons (2006)

Piston pins

■2002 NV5A: Material HM235, hard chrome plating, weight 41 g, pin diameter 17 mm
■2003 NV5B: Material HM235, hard chrome plating plus tungsten carbide coating, weight 37.2 g, pin diameter 17 mm
■2004 NV5C: Material HM235, tungsten carbide coating, weight 37.6 g, pin diameter 17 mm
■2005 NV5D to 2006 NV5HD: Material HM235, diamond-like carbon coating, weight 38 g, pin diameter 17 mm
■2006 NV5HG: Material HM235, diamond-like carbon coating, weight 29.7 g, pin diameter 15 mm

Honda used HM235, an iron-based material, for all of its piston pins. They were originally surface treated with a hard chrome plating, with reverse currents applied during this process creating a porous surface (with countless small holes) that allowed engine oil to penetrate the surface and create good lubricating properties. However, this treatment caused problems, with the porosity leading to peeling of the plated surface and resulting in connecting rod small end damage. For this reason, Honda gave up on the hard chrome plating and changed to a tungsten carbide (WC) coating treatment (applied using vapor deposition) in the middle of the 2003 season. It changed again for the NV5D in 2005, and later models, to a diamond-like carbon (DLC) coating treatment.

From the NV5A in 2002 to the NV5HD in 2006, Honda used 17 mm diameter piston pins. However, with its decision to downsize the NV5HG in 2006 to reduce the moments of inertia, it reduced diameter considerably to 15 mm. While piston pin weight had been pared back to 38 g from the NV5A’s original 41g, this change in pin diameter for the NV5HG took another 10 g off at once.

Connecting rods

■2002 NV5A: Material titanium, small end copper bushing
■2003 NV5B to 2004 NV5C: Material titanium, small end oxygen diffusion treatment
■2005 NV5D to 2006 NV5HD and NV5HG: Material titanium (hollow), small end copper bushing

Honda developed a number of four-stroke racing engines for motorcycles, such as the VFR750R (RC30) and RVF (RC45), that used titanium connecting rods treated with an oxygen diffusion (OD) process as an anti-seize treatment. This process was also applied on the NV5A, the first of the RC211V models. In testing just prior to its competition debut, however, it blew up an engine when wear and tear on the OD-based hardened layer caused expansion of the connecting rod small end holes. Naturally, it took some time before it could find a solution, so for the first few rounds of the 2002 season, it decided to replace the connecting rods with new ones every 300 km, which was about one-sixth the originally planned frequency. With this workaround, it just managed to get through the season by overhauling many more engines than planned for each race. During this time, the engine developers developed a technical solution that involved pressing a phosphor bronze (copper) bushing into the connecting rod small end holes. While the softness of the phosphor bronze inevitably resulted in galling when press-fitting the bushings, Honda applied a WC coating to bushings that were more resistant to galling and then used the technology in racing to get through the second half of the 2002 season.

For the NV5B in 2003, Honda returned to treating the connecting rod small ends with the OD process, and also changed the surface treatment of the piston pins, which slide against the small ends, to a WC coating to achieve a more stable result. Then for the NV5D in 2005, it started using hollow connecting rods as part of its commitment to reducing weight. While changing the small end bushing material to beryllium copper, it also adopted the DLC coating treatment for the piston pin surface. With these specifications applied during the 2005 and 2006 seasons, Honda experienced no more connecting rod-related problems.

As for crank shaft material, Honda used NT100 nitriding steel throughout.

NV5HG connecting rods (2006)

Intake/exhaust value angle and intake/exhaust valve diameter

■2002 NV5A to 2003 NV5B: Valve angle 11° intake and 13° exhaust, valve diameter 29.5 mm intake and 24.5 mm exhaust
■2004 NV5C: Valve angle 10.5° intake and 12.5° exhaust, valve diameter 31 mm intake and 25.5 mm exhaust
■2005 NV5D: Valve angle 10.5° intake and 12.5° exhaust, valve diameter 31.5 mm intake and 25.5 mm exhaust
■2006 NV5HD＆NV5HG: Valve angle 10.5° intake and 12.5° exhaust, valve diameter 31 mm intake and 25.5 mm exhaust

The RC211V V5 engine started with a bore of 73.0 mm and stroke of 47.3 mm, which was changed to 75.0 mm and 44.8 mm respectively for the NV5C in 2004. At the same time, intake-exhaust valve angle for both intake and exhaust sides was reduced by 0.5° to create more upright valves and the shape of the combustion chambers was enhanced. This valve angle was then maintained until the NV5HG, the final model in 2006.

Made of titanium, the intake and exhaust valves had the same diameter for the NV5A in 2002 and NV5B in 2003. However, when the cylinder bore was increased in size for the NV5C in 2004, intake and exhaust valve diameters were also increased by 1.5 mm and 1.0 mm respectively. For the NV5D in 2005, laser cladding technology, which uses a laser beam to add a layer of metal to a surface, was used to integrate the valve seat area with the intake and exhaust ports and further increase the diameter of the intake valve by 0.5 mm. Honda finally returned the intake valve diameter to 31 mm, the same as the NV5C, for the NV5HD and NV5HG in 2006.

Intake/exhaust valve springs

■2002 NV5A to 2005 NV5D: SPEC 1
■2006 NV5HD: SPEC 2
■2006 NV5HG: SPEC 3

As of 2024, MotoGP engines from all manufacturers, without exception, employ the pneumatic valve return system (PVRS), which uses air pressure to operate poppet-style intake and exhaust valves. Honda also adopted this system for its MotoGP engines from the middle of the 2008 season. However, this technical article is focused on RC211V machines produced between 2002 and 2006, and during this period it used metal valve springs.

Put simply, the valve springs were made from steel, but with a chemical composition that satisfied requirements for thermal resistance, mechanical properties, cold working properties, and heat treatability. They were subjected to a range of treatments and processing, including coiling at high temperature, immersion in oil at a temperature of approximately 500 degrees Celsius, and carbonitriding of the material surface, to create the final parts. They incorporated a wealth of know-how. From the era of “Asama racers” in the 1950s, Honda has always created high revving engines that were ahead of the times, with its high performance valve spring technologies being part of that history. As the times changed, it created valve spring materials to withstand the ever-increasing stresses involved, with the RC211V also using the best materials available at the time.

Prior to the introduction of PVRS, the maximum engine speeds of Honda’s high performance four-stroke engines depended greatly on valve spring performance. This required extremely precise control of parameters including, not just the choice of material, but things like spring winding pitch and linearity as well. For the RC211V, maximum engine speed with the NV5A in 2002 was 15,000 rpm, but by the final NV5HG in 2006, the valve springs had to guarantee engine speeds up to 17,000 rpm.

Engine oil lubrication method

■2002 NV5A to 2006 NV5HD and NV5HG: Semi-dry sump

Honda employed the same engine oil lubrication method on all of its RC211V machines, from the first NV5A in 2002 to the last NV5HG in 2006. It was a semi-dry sump system with the transmission housing acting as the oil tank. The structure had three scavenging oil pumps separately located in three sealed crank throws, with the engine oil and blow-by gas discharged to the transmission housing side. The oil would then fall from the transmission housing into the oil pan. When the engine was running, a negative pressure of up to 70 kPa would build up within the crankcase, which reduced both pumping loss (due to the design of the back of the pistons) and oil agitation loss (due to the design of the crankshaft). This improved maximum engine output by 4% and reduced friction by 19% compared to a normal wet sump. The RC211V’s semi-dry sump was also located integrally with the engine, enabling a weight reduction of approximately 1 kg compared to a completely dry sump that required a separate oil tank and plumbing.

During actual racing of the RC211V in 2002, scratching occurred on the sliding surfaces of the shift fork, which became a problem. It was caused by increased load on the area where the shift fork slid against the gears, resulting in higher surface pressure and therefore increased sliding resistance. During the 2003 season, Honda temporarily provided channels for directing a portion of the engine oil in the crankcase onto the shift fork to improve lubrication and cooling. This structure was incorporated from the beginning of the design stage for the NV5C in 2004, and continued on in subsequent models from the NV5D in 2005.

Crankcase structure

Fuel supply system

■2002 NV5A to 2006 NV5HD and NV5HG: Dual injector system

A few of the four-stroke MotoGP machines that competed in the 2002 season, which was the first year of the MotoGP, were carburetor-based systems. Honda, on the other hand, approached engine development from the start with the intention of using electronically controlled fuel injection. This system employed two injectors for each cylinder; one each at the upstream and downstream sides of the throttle bodies. The upstream injectors, used for operation under high loads (full-throttle), and downstream injectors, used for operation under low loads (partial-throttle), operated sequentially to balance rideability and high output power. Honda also developed deflective multi-hole injectors that it used to enhance fuel atomization performance.

The system incorporated a servomotor-based mechanism for continuous control of fuel injection pressure, and a mechanism for predictive control of fuel amounts adhering to the inside of the intake ports when opening and closing the throttle and flowing into the combustion chambers during the next combustion cycle. This achieved high levels of throttle controllability, rideability, and fuel economy. With constant fine tuning as well, Honda continued using this dual injector system through to the NV5HG, the final model in 2006.

Dual injector system

Throttle bore diameter

■2002 NV5A to 2003 NV5B: Diameter 48 mm
■2004 NV5C to 2006 NV5HD: Diameter 48 mm-equivalent oval
■2006 NV5HG: φ48mm

All RC211V engines used a throttle bore diameter of 48 mm ahead of the intake port. The NV5A in 2002 and NV5B in 2003 used a standard circular-shaped bore, whereas the NV5C in 2004 used a vertical oval-shaped bore with the same area. The reason for the change was to increase combustion efficiency of the atomized fuel by moving the downstream injectors, used for operation under low loads, closer to the intake ports. The oval throttle bores were used for the NV5D in 2005, and for the NV5HD that used the same design in 2006. However, when Honda redesigned the NV5HG engine for overall compactness in 2006, it returned to the original circular throttle bores.

Honda had been using a variable-length intake trumpet (funnel) mechanism since the beginning of the 1990s when it introduced it to its F1 racing car engines. For motorcycle racing engines, on the other hand, while this mechanism was used on the RVF (RC45) Superbike racer at the end of the 1990s, it was not used on the RC211V when it debuted in 2002. The main goal of the variable intake trumpet mechanism was to improve charging efficiency of the air-fuel mixture by lengthening the trumpet when riding at low engine speeds to increase the inertia effect of intake air. At the time, Honda felt that ease of handling and controllability were more important than peak output for creating an outstanding MotoGP engine and machine package, so it decided not to use the mechanism. However, as time went by, performance requirements increased as well, so that the latest Honda MotoGP machine, the Honda RC213V, now also uses the variable intake trumpet mechanism.

Exhaust layout

■2002 NV5A to 2003 NV5B: Five-into-two (cylinders #1, #3, #5 and cylinders #2, #4)
■2003 NV5B to 2006 NV5HG: Five-into-three (cylinders #1, #5, cylinder #3, and cylinders #2, #4)
■2004 NV5C (Big-Bang): Five-into-four (cylinders #3, #5, cylinder #1, cylinder #2, and cylinder #4)

The performance development team was in charge of determining exhaust pipe specifications, while the chassis development team was in charge of determining actual layout of the exhaust pipes based on those specifications.

Honda started its RC211V V5 engines with an exhaust layout that collected exhaust from the three cylinders in the front bank and the two cylinders in the rear bank to finish with two separate pipes. In the middle of the 2003 season, it changed layout to take exhaust separately from cylinder #3 in the middle of the front bank as well, finishing with three separate pipes. It then maintained this three-pipe layout for all irregular interval ignition engines through to its final RC211V model, the NV5HG in 2006.

From the middle of the 2003 season, Honda adopted an exhaust layout that brought the two pipes from the front bank down the right side of the machine for a total of three pipes. This design was possible because the Unit Pro-Link rear suspension system was slightly offset to the left. However, after moving the Unit Pro-Link system to a center position for the NV5HG in 2006, the two pipes coming from the front bank were separated down the left and right sides of the machine.

For the NV5C engine in 2004, the specifications were changed to an irregular interval, two-cylinder simultaneous ignition (Big-Bang timing), with an exhaust layout using four pipes. To achieve as straight a flow as possible for the Big-Bang exhaust pulsation, exhaust was taken separately from each cylinder except for cylinders #1 and #5 in the front bank, which were combined into one pipe.

Exhaust layout（2002 NV5A）

Throttle control

■2002 NV5A: Direct wired
■2003 NV5B to 2006 NV5HD: HITCS (wire input)
■2006 NV5HG: HITCS-2 (throttle-by-wire input)

All RC211V machines employed butterfly-type throttle valves, which have excellent controllability. The mechanism used on the first-generation model NV5A in 2002 brought a wire straight from the throttle grip to control throttle valve opening and closing. It had a throttle wire pulley, with an elliptical shape, located at the end of the shaft that held the throttle valves. This enabled Honda to avoid a 1:1 relationship between the opening of the rider’s throttle grip and the amount of throttle valve opening, with the aim of achieving a gentler opening of the actual throttle valves at the start of throttle opening.

As an electronic control with the same philosophy, Honda introduced its Honda Intelligent Throttle Control System (HITCS) to the NV5B in 2003. The main point in incorporating electronic control into throttle valve opening and closing on all five cylinders, and controlling actual throttle valve opening to a lesser degree than the rider’s throttle operation, was to suppress excessive driving force when using low gears in particular.

Honda used a second-generation evolved HITCS throttle on the NV5HG in 2006. In this case, throttle valve opening and closing was electronically controlled only for the two cylinders in the V5’s rear bank, with throttle valve opening of the three cylinders in the front bank directly linked to opening of the throttle grip. This increased linearity of throttle operation by the rider and enabled more precise control at the start of throttle opening and at full throttle.

Throttle input until the first-generation HITCS was via a wire extending from the throttle grip. With the arrival of the second-generation HITCS-2, however, Honda adopted a throttle-by-wire system that converted wire movement to electronic signals to drive the servomotor that opened and closed the throttle valves. This made it easier to set any throttle opening position.

HITCS-2 structural diagram

Deceleration control

■2002 NV5A: Solenoid valve-based air intake control
■2003 NV5B to 2006 NV5HD: HITCS-based air intake control
■2006 NV5HG: HITCS-2 (throttle-by-wire)-based air intake control

As of its debut season in 2002, the RC211V already had a top speed of approximately 320 km/h. However, because a straight is always followed by a corner on a racing circuit, deceleration performance is extremely important for reducing lap times.

One of the greatest ways to enhance deceleration performance is to properly control the strength of engine braking when the throttle is fully closed. For this reason, Honda focused on the philosophy of deceleration control from the start of development of its RC211V.

For the NV5A in 2002, the first-generation model, Honda developed and introduced a system to damp down engine braking, with air inlets provided in the air intake channels after the throttle valves, and solenoid valve-based electronic controls, to ensure appropriate amounts of air entering the air intake channels for engine combustion even with the throttle fully closed.

For the NV5B in 2003, Honda adopted HITCS, which incorporated electronic control into throttle valve opening and closing. It also used it for deceleration control to slightly open the throttle valves under full braking even the rider has fully closed the throttle. At the same time, Honda gradually combined controls for ignition timing and fuel injection amounts, such as preventing fuel injection if the throttle is closed off too suddenly, for example. Then for the NV5HG in 2006, the throttle-by-wire based second-generation HITCS installed on this model was used to achieve even more precise air intake control.

2002 Australian Grand Prix

Clutch-based deceleration control

■2002 NV5A to 2005 NV5D: Back-torque limiter
■2006 NV5HD: Slipper clutch with assist
■2006 NV5HG: Back-torque limiter

Even when closing the throttle completely to cut engine torque under hard braking, the rear wheel will continue to rotate at high speed. This creates an imbalance between engine-side and rear wheel-side torque, with the rear wheel losing grip and snaking on the road, creating an extremely unstable situation for the machine. The mechanics of this situation also create a torque that pushes back against the engine side from the rear wheel side, which also contributes to unstable machine behavior and places an unnecessary load on the engine.

This torque pushing back on the engine from the rear wheel is called “back torque.” It is established practice for road racers, equipped with four-stroke engines with strong engine braking, to add a back-torque limiter to the clutch as a mechanism for mitigating this effect. The RC211V was also equipped with this mechanism from the NV5A in 2002, the first-generation model.

Called a “slipper clutch,” it uses ramp inserts with a wedge-shaped cross section as cams, and adds a back-torque limiter to create or resolve a half-clutch state in accordance with the degree of back torque in the system. In other words, all engines over successive generations of the RC211V were equipped with a slipper clutch.

The V5 990cc engines generated a considerable amount of torque (up to 119.0 Nm for the NV5C in 2004). To transmit that torque without loss, a high spring rate, pressing the clutch disc against the flywheel, was required. This created a very heavy clutch operation that was a major burden to riders with weaker grip strength. It was possible to reduce the amount of strength required to operate the clutch lever by changing the master cylinder diameter ratio, but that could have created a situation where the clutch would not sufficiently disengage. At that point, Honda adopted a slipper clutch with a mechanical assist mechanism in 2006 to lighten the clutch operation. However, the assist was difficult to control and riders felt that if they were not fully focused on operation, the clutch could engage suddenly.

Honda’s works riders in 2006 were Nicky Hayden and Dani Pedrosa, with the much smaller Pedrosa using the slipper clutch with assist throughout the season. Hayden, on the other hand, had higher grip strength and, while he also used this new assist mechanism during the first rounds of the season, he used the previous slipper clutch, without assist, for the rest of the season.

Engine unit weight

■2002 NV5A: 60.40kg
■2003 NV5B: 62.80kg
■2004 NV5C: 61.90kg
■2005 NV5D: 61.96kg
■2006 NV5HD: 61.96kg
■2006 NV5HG: 57.29kg

Honda set and achieved a target engine unit weight of 60 kg for the NV5A in 2002, the first of its RC211V models. (Note: Engine unit weights above include throttle bodies and are final specifications at the end of each season.) However, weight was increased by 2.4 kg for the NV5B in 2003 after a series of efforts to reinforce parts in response to trouble experienced during the 2002 season. With the NV5C in 2004, however, it was able to claw back 1.1 kg of this weight through various changes and other efforts, including changing bore and stroke specifications.

Almost 10 engines with different specifications were developed for the NV5C, depending on how they are counted, so engine development for the NV5D in 2005 was based on the NV5C specifications judged to have produced the fastest times. Honda then experienced many engine-related problems, perhaps due to going too far with the changes, so it implemented measures that increased final engine weight specifications for the NV5D by just 60 g compared to the final NV5C specifications.

The NV5HD engine in 2006 was based on final specifications for the NV5D, so engine weight was the same. With solutions fully implemented on the NV5D, the NV5HD experienced almost no engine-related problems. On the other hand, Honda made bold changes to create a more compact engine for the NV5HG in 2006, resulting in an engine that was 4.67 kg lighter than the NV5HD in the same year. Even so, the maximum output of the NV5HG was almost 4% higher than the NV5HD as the culmination of all RC211V V5 engines before it.

NV5HG engine (2006)

ECU functions and electronic controls

As of 2024, every motorcycle manufacturer competing in the MotoGP are using the same electronic control unit (ECU). This is the outcome of regulations in 2014 that required the same ECU hardware to be used for all machines, followed by regulations in 2016 that required the same software to be used as well. The aim was to reduce the overheating competition and increasing costs of development among manufacturers. Conversely, this showed how sophisticated electronic control technologies had become by the middle of the 2010s, with even Honda developing and using its own ECU hardware and software. From this perspective, while electronic controls were employed on RC211V machines competing in the early years of the MotoGP, they were extremely primitive.

When it made its racing debut in April 2002, the top priority with the RC211V was reliability, while there was very little active electronic control used. By the middle of the 2002 season, the first controls were being implemented in the form of traction control. But even those controls were limited to ignition timing and fuel injection amounts.

While Honda also implemented wheelie control from the middle of the 2005 season, even this was limited to parameters controlling the difference between rotating speeds of the front and rear wheels and the length of stroke for front and rear suspension systems.

Maximum output, maximum torque, and compression ratio

■2002 NV5A: 175.5 kW @15,000 rpm, 117.4 Nm @11,500 rpm, compression ratio of 13.5
■2003 NV5B: 183.0 kW @15,500rpm, 117.1 Nm @11,500rpm, compression ratio of 13.5
■2004 NV5C: *188.1 kW @16,500rpm, 115.5 Nm @13,500rpm, compression ratio of 13.3
■2005 NV5D: *184.0 kW @16,500rpm, 113.2 Nm @13,500rpm, compression ratio of 13.3
■2006 NV5HD: *183.5 kW @16,500rpm, 114.0 Nm @13,000rpm, compression ratio of 13.2
■2006 NV5HG: *190.2 kW @17,000rpm, 116.0 Nm @14,000rpm, compression ratio of 13.9

Note: Figures above are final specifications for each model.
Figures marked with an asterisk (*) are values after test bench calibrations conducted in October 2004.

The NV5A, the first of the RC211V models, produced maximum engine output of 166.75 kW, or 226.7 pferdestärke (PS), when it made its racing debut in April 2002. In testing just prior to its debut, the connecting rod small ends sustained damage, so reliability was only marginal and maximum engine speed was limited to around 14,500 rpm. After modification upon modification, the NV5A engine achieved 175.5 kW (238.6 PS) by the end of the season, representing an increase of approximately 5% in output and an increase of 500 rpm in engine speed.

In a normal evolution over the previous year’s model, the NV5B in 2003 offered approximately 4% higher output. For the NV5C in 2004, Honda developed irregular interval, two-cylinder simultaneous ignition (Big-Bang timing), in addition to its previous irregular interval ignition, and introduced almost 10 engines with different specifications during that season alone. The NV5C Spec 2 Modified (irregular interval ignition), ridden only by Max Biaggi in the final round of the season, produced the highest engine output and achieved a top engine speed of 16,500 rpm.

In October of the same year, HRC conducted engine test bench calibrations and confirmed that measurements after calibration were roughly 3 kW lower for the same engines. The maximum output and maximum torque above for each model from NV5C are values after these test bench calibrations.

Although the NV5D engine in 2005 was based on the NV5C Spec 2 Modified engine, it experienced lots of trouble. For this reason, Honda had to operate the engine at lower output levels to prioritize reliability. This was the reason for maximum output for the NV5D being lower than that of the previous year’s NV5C. Honda ran two different RC211V machines, the NV5HD and NV5HG, concurrently in 2006, which was the last year that the MotoGP restricted maximum engine displacement to 990cc. While maximum output and maximum engine speed for the NV5HD were largely unchanged from the NV5D, the NV5HG produced almost 4% higher maximum output than the NV5HD, with maximum engine speed of 17,000 rpm. This was due to a new design that delivered a much more compact and lighter engine. This became the driving force behind Honda recapturing the triple crown of rider, team, and constructor titles that year.

Comparison of engine output and torque for
the 2006 NV5HD (original) and NV5HG (new generation)