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Honda NR 500 GP Racer 1979
When Honda returned to GP racing after
a 12-year absence in 1979, they did so with astonishing new four-stroke
technology to challenge the reigning two-strokes: The remarkable V-4 oval-piston
NR500.
There were many versions of the NR, each pioneering technology still in vogue
today.
The NR stands for New Racing, and the New Racing division was exactly that: the
NR team was made up of all young engineers guided by the father of the
six-cylinder CBX and fabled RC166, Soichiro Irimajiri, and project leader Takeo
Fukui who later become director of R&D and President of HRC.
The NR was essentially a V-8 with each
set of adjacent cylinders fused together. Each oval cylinder housed eight valves
that doubled the valve area possible in a conventional V-4. The oval piston
measured 93.4mm x 41mm, and was held by two connecting rods moving through a
super-short 36mm stroke. This allowed the NR to reach engine speeds of 19,500
rpm—twice the speed of the two-strokes—and produce horsepower comparable with
the 500GP two-strokes.
Honda mythology tells of Irimajiri's epiphany of the oval piston while observing
an oval traffic light on his way to work.
Concepts developed in the NR echo
prophetically in race technology today: side-mounted radiators, still common to
V-4s today, back-torque limiters; magnesium engine bits; carbon fiber
componentry including skeletal frame, carbon wheels, swingarm, fork tubes, and
brakes.
The second-generation NR500, the 0x model, featured a Monocoque aluminum frame
in which the fairing is an integral part of the chassis.
The Oval Piston: Heart of a New and
Different Breed
To design a 4-stroke, 4-cylinder engine in the
conventional manner would not produce a machine that could out perform its
2-stroke rivals. No, for a 4-stroke engine to generate the same level of output
as a 2-stroke engine it had to have twice as many cylinders as its competitor.
Moreover, 20,000 r.p.m. was the absolute minimum a 4-stroke engine required to
produce superior horsepower.
Increased power meant that the 4-stroke engine would have to consume and exhaust
more of the critical fuel-air mixture. In other words, the aperture of the valve
would have to increase for enhanced intake and exhaust efficiencies. To do that,
the number of valves would increase, also. However, conventional circular
pistons would accommodate only four or five valves. Furthermore, such a
structure would provide no technical advancements, as compared to the time when
Honda was competing in the World GP with its 4-valve DOHC engines. Therefore,
the NR project's new challenge was to achieve "innovative technology," being
more than a mere refinement of the previous technology.
Winning is the essence of racing. Thus, in winning the race, the team could
prove that its technology was superior. Hence, there was no significance in
creating a machine that was not capable of winning. That would lead neither to
technical progress nor to the fostering of outstanding new talent. However, the
Honda NR development team knew that to make a comeback in the World GP meant the
establishment of a training ground for young talents; people who would strive to
improve their skills through the creation of truly great motorcycles. If there
were no chance of winning the race or fostering talent, Honda would be better
off not trying at all.
Honda's answer was the adoption of an oval-piston design. With eight valves
lined up atop the pistons, each supported by two connecting rods, the team's new
4-cylinder engine looked like an 8-cylinder. According to Fukui's calculation,
the engine could potentially reach a maximum speed of 23,000 rpm and output of
130 horsepower. Therefore, the target output was set accordingly, at 130
horsepower.
However, the oval-piston design necessitated an extremely difficult
manufacturing process, in which machining accuracy would be more critical than
ever. Of course, no such design had been adapted for use in a high-performance
racing machine. Nevertheless, the spirit of Honda was never to be pessimistic,
and the team decided it was worth trying as long as there was a real
possibility. In making such a decision the team was well aware of the difficult
path ahead. In order to beat 2-stroke engines, they had to transcend
common-sense thinking and bring in daring new technologies.
The concept for Honda's new engine was finalized in April 1979, and the NR Block
set as its primary goal the realization of an oval-piston engine. The team faced
difficulties right from the start. In fact, they had to prove that oval pistons,
cylinders, and piston rings could actually be made. They also had to find a
manufacturer that could help them do it.
Finally, the team commissioned the production to an associate company, Honda
Metal Technology, located in the city of Kawagoe, Saitama Prefecture.
Development went forward there, but the process was not entirely free of
problems. Since in an oval piston a semicircular curve has to merge into a
straight line, continuous curvature could not be maintained and edges were
created along the piston. This made machining very difficult. Similar problems
were found in the honing of the cylinder's inner diameter, and many hours were
spent in production.
The team members in charge of engine design had their own private concerns, but
spirits were high in the NR Block, where team personnel worked eagerly to prove
that their engine was more than a fantasy.
In July 1978, three months after the start of production, the NR team finally
completed a dual-valve head, 125-cc single-cylinder engine prototype, which they
named "K00." Contrary to the team's concerns, the engine turned properly on the
bench tester. With renewed confidence, the NR Block continued its efforts and
the following October completed an eight-valve head, water-cooled,
single-cylinder engine, the K0. Each day was spent making a prototype, testing
it, modifying the specifications, and testing it again. Repeated testing
revealed that the oval-piston design would cause problems at speeds in excess of
10,000 rpm, due to poor machining accuracy and the loss of durability.
Regardless, the team members knew they could not continue testing
single-cylinder engines indefinitely.
The NR Block was in fact developing a 4-cylinder engine commensurate with the
testing of single-cylinder units. In April 1979, they completed a 4-cylinder
V-engine called the "0X," which was to become the heart of the NR500. During the
bench test, the engine produced 90 horsepower, making it clear that they had not
yet reached their target of 130 horsepower.
The NR Block had also formed a new materials
group in order to study two key problems-machining accuracy and durability. The
group leader was to be Yoshitoshi Hagiwara, then chief research engineer in
HGA's Third Research Block, who had been collaborating with the development team
since the early stages of development. One of the group's key responsibilities
was to collect the engine parts broken during testing and investigate their
causes of failure. It was a tedious task in which it was often necessary to go
through the pieces of several parts one by one and divide them into rings,
valves and so forth. The group even studied new materials such as carbon and
complex high-tech materials, along with enhanced manufacturing techniques that
might be used to build parts which could withstand high engine revolutions.
Ultimately, these efforts were fruitful, producing notable improvements in
durability.
It was not just the engine that was
unconventional. To increase its competitiveness, the NR500 also employed a frame
technology that was simply unheard of in the conventional realm of engineering.
Tadashi Kamiya, a research engineer in HGA's Third Research Block who had joined
the NR program in the summer of 1978 as chief of the test group for completed
product, proposed several ideas that he was thinking could be adapted for use in
production cars. One of them was an aluminum frame called the "shrimp shell."
The shrimp shell, which integrated a monocoque structure with the cowling to
form the frame and body, virtually encased the engine, which was then inserted
through the rear like a cassette. The engine was fixed with 18 six-millimeter
bolts inserted at both sides. Although the panel was paper-thin at just 1 mm,
once the engine was in place the frame was able to ensure the required rigidity.
Additionally, the frame weighed just 5 kg, which was about half the weight of an
ordinary tubular steel frame.
The idea, not surprisingly, encountered outright confusion among the members of
the NR Block. In order to convince his colleagues Kamiya created a prototype
model and, the members understood the concept of his shrimp-shell frame.
The second idea involved the wheel. Kamiya thought of adopting a 16-inch wheel
instead of the mainstream 18-inch wheel.
"By reducing the tire diameter," Kamiya said, "we could reduce the machine's
weight by around 4 kg and vehicle height by around 5 cm. The lower air
resistance and smaller disc diameter also contributed to a lower moment of
inertia, enabling the machine to accelerate faster. Moreover, the reduced
frontal projection had the effect of increasing output by several horsepower.
"When I compared the 18-inch wheel with the 16-inch wheel, I asked myself which
of the two would cross the finish line first in actual races, where average
speeds often exceeded 200 km per hour, I was convinced that the 16-inch wheel
had greater potential, not simply from the standpoint of partial speeds at
corners but by putting all the elements in proper perspective."
Kamiya also adopted a vertical standing screen to be attached to the cowling,
instead of the regular semispherical type.
"You could call it an invisible cowling," he said. "With this design we can
still achieve sufficient aero-dynamic effect. Since the wind is directed upward
after hitting the screen, the rider is subjected to less wind resistance at high
speeds. Also, the area of frontal projection becomes smaller."
Another idea involved the swingarm and drive sprocket, which were positioned
along the same axis. Because chain length was no longer affected by the upward
or downward movement of the swingarm, there was no need to provide extra play.
This meant an advantage in reducing shock due to acceleration or deceleration,
thus stabilizing the suspension's performance over an entire course.
Kamiya believed that no 4-stroke engine,
regardless of its merits, could win with a frame design based on conventional
thinking. Thus, the NR's frame was constructed from the standpoint of minimizing
volume and weight. The staff sought to create a 125 cc frame capable of carrying
a 500 cc engine. These were just examples of the many unconventional, even
outrageous, ideas being implemented in the new machine. However, they were all
based on strategies that had been calculated to an absolutely meticulous degree.
The NR500 was put to the first test ride in Yatabe, Ibaragki Prefecture, in May
1979. Although the road test brought up problems that the team had failed to
identify in bench testing, these were gradually resolved through refinement of
the engine in repeated tests at Suzuka Circuit and on the course at Tochigi. The
NR500 became more complete with each passing day, and soon it would be ready for
its first World GP event. Due to a significant delay in the NR500's overall
development schedule, though, its comeback had to be pushed back to the British
Grand Prix, which was to be held at Silverstone on August 12.
The NR500 was at last completed in July 1979. Equipped with a 4-cylinder
V-engine and 100-degree cylinder banks, the machine had a maximum output of 100
ps at 16,000 r.p.m.
The NR team had finally made it to England,
where the machines were receiving their final tuneups in preparation for the GP
race. At the same time, Yanase was making various arrangements in order that the
team might concentrate on the race free of hindrances. Thus, in addition to
setting up the bikes for optimal performance on the track, there were many other
things that had to be done for each race, such as arranging transportation and
accommodations for the many staff members involved. The World GP, often referred
to as the Continental Circus, had most of its races in Europe. Therefore, while
it was possible to develop the motorcycles in Japan, it was impossible to manage
the races from Japan. The distance was simply too great.
Yanase rented a warehouse in Slough, an English town near Heathrow International
Airport, as their team's base of operations in Europe, while in Britain
additional preparations were underway through a company called HIRCO (Honda
International Racing Corporation). Honda had established HIRCO in December 1978
as a joint venture with Honda UK for the management of all racing activities,
including competition in the World GP series.
Honda's riders for the 1979 season would be Mick Grant and Takazumi Katayama,
the latter having competed in the 1977 World GP series as a privateer, where he
ultimately won the championship title in the 350-cc class.
For their part, the NR500s kindled great
expectations upon their appearance at Silverstone, portending awesome
performance with their original engine design and sleek styling. However, those
expectations were mercilessly shattered in the qualifying round. These bikes,
which were still in development, barely performed well enough to get through to
the final. Even then, Grant fell at the first corner following the start and
quickly retired. Katayama also retired after several laps due to ignition
problems.
Though they had not expected a win in their very first race, the NR team was
deeply disappointed with the outcome of their efforts. The NR500s were brought
back to Japan, and improvements were made to further reduce weight and increase
output. However, those really were not the fundamental solutions that the
project team had long sought.
Harsher realities awaited in the French GP, the twelfth race of the 1979 season
where both machines failed to qualify for the final, meaning that no results
whatsoever could be garnered from their presence. However, the team could not go
back to Japan without data, after having spent so much time and money in
preparation for the French event.
Therefore, the staff of the NR Block flew to England, and with help from HIRCO
tested the NR500s at Donington Park. The test was a fruitful one, in which new
areas of possible improvement were identified. However, there was no improvement
in speed, and the machines were still running two seconds behind the lap record.
In the world of racing, where one-hundredth of a second determines the winner,
two seconds was just too great a handicap.
Having finished the 1979 season with
disappointing results, the NR500s had two major problems that were considered
unique to 4-stroke engines.
First, was the factor of extreme engine braking. When development began, the
team viewed engine braking as an advantage, believing it would assist in overall
control of the bike. On the contrary, the engine braking caused the rear wheel
to hop. To counteract it, the team developed a back-torque limiter with a
built-in, one-way clutch so that the wheel would spin when the force applied to
the wheel exceeded a certain level. This methodology was later incorporated in
the VF750F, making it the first production bike to be equipped with a
back-torque limiter.
Acceleration was the second problem. It simply did not provide the necessary
subtlety of control. The ability of the engine to generate ample low-end
torque-a characteristic of 4-stroke engines-also made cornering control
difficult, resulting in the loss of time. During the 1980 season the team
experimented with throttle pulleys based on various shapes, but as yet there was
no solution.
Weight was another area in need of attention. Although the first 0X engine was
lighter than the average 2-stroke engine, weight gradually increased as
durability improved. Before long, the engine had put on as much as 20 kg. The
development team conducted an exhaustive review of materials, going to titanium
and magnesium in order to achieve weight reduction. However, the new material
combination was quickly copied by rival teams, leaving Honda with no advantage
in that area.
The shrimp-shell frame, which had so greatly contributed to weight reduction,
also had a drawback. Because of its cassette-type mounting structure, the engine
had to be removed from the frame in order to perform maintenance. This made it
difficult for the engineers to achieve optimal settings within the limited time
allowed in the qualifying runs. Accordingly, the team decided to adopt a pipe
frame to the machines, beginning in 1980. At the same time, the wheel size was
changed to 18 inches.
Ultimately, the problem with the NR500 was that so many new technologies had
been introduced that its potential for completion had been compromised.
Realizing this, the NR Block prioritized problem areas, placing the top priority
on refining the engine. This, they believed, was the most fundamental problem of
the bike.
The new and greatly improved NR500s competed in an international race held in
Italy. Although it was not a World GP race, Katayama was able to take the podium
with a third-place finish. He also put up a good fight in the final round of the
British World GP, held that August. The fifteenth bike to pass the finish line,
his machine was the first NR500 to finish a GP race. Moreover, Katayama made a
strong showing in the West German Grand Prix, finishing in twelfth place.
The 1980 season, however, closed with just two events in which Honda's NR500s
made it to the final round. Still, the machines were making steady progress, so
it was still possible to build a point total and finish the season in tenth
place or higher. However, the reality was that they were still trailing the
2-stroke machines by 10 or more horsepower. Therefore, even if the NR500s could
advance in the standings, they did not have what it took to win a GP race.
Yanase recalled a sentence in the plan document he had received in December
1977. It read, "Become the world champion within three years." He knew that 1981
would be the final year in that attempt, so there was not much time left.
The oval piston engine underwent further
improvements in order to reduce its weight, enhance output, and improve
durability. The improved engine intended for the 1981 season had a smaller body,
made possible by dropping the V-bank angle from 100 degrees to 90. Moreover, it
had a maximum output of 130 ps at 19,000 rpm. Therefore, beginning with the 1981
season, Honda decided it wouldn't just compete in the World GP, but that it
would also enter the All-Japan Championship Series. Honda made the decision to
refine its NR500s more rapidly through participation in more races, hoping to
build winning machines as quickly as possible.
In the second race of the All-Japan Championship, held at Suzuka Circuit in
March 1981, the two NR500s ridden by Katayama and Kengo Kiyama both fell and
retired. However, they had demonstrated considerable tenacity during the race,
advancing to a point just behind the top group. In the next race held at Suzuka
in April, the team saw one of its NR500s finish in fifth place. By this time,
the NR500s were performing at levels equal to those of their 2-stroke
counterparts.
Yoichi Oguma, the chief research engineer from HGA's Second Research Block who
had joined the NR project in 1981 and became the first manager of the Honda
Racing Team (HRC) the following year, had one vision: "Tactics and strategies
also are important in winning the race. Honda is so preoccupied with the
performance of its machines, but we can't win unless the machines, the riders
and the team work as one."
This was a conviction that Oguma, a former All-Japan champion in the 125 cc
junior class, had acquired through his own experience. Reflecting on that
belief, the Suzuka 200-km Race-the sixth All-Japan race held in June 1981-was
run under his careful supervision, according to a calculated strategy.
Any 2-stroke engine running a distance of 200 km, or 34 laps of the Suzuka
Circuit track, will require at least one pit stop in order to refuel. That means
approximately 10 seconds in the pit area. Considering that the bike must
decelerate to enter the pits and accelerate again on its return to the course,
nearly 20 seconds must be given up. Oguma's strategy was to let his machines run
the entire race without a fuel stop by making use of their higher fuel
efficiency, which was of course the advantage of 4-stroke design. According to
his calculations, the NR500s would save around 0.6 second per lap by eliminating
the fuel stop.
The race was carried out according to plan. While the rival machines were making
their fuel stops, Kiyama's NR500 gradually advanced, eventually passing the
leader on lap 23. It was the first time an NR500 had led a race. What's more,
Kiyama maintained his time, leading the race lap after lap. Coming out of the
last corner first, his NR500 kept its lead and took the checkered flag. Three
years after the start of development, the NR Block and its NR500 had achieved a
victory.
The team was again victorious in July, when Freddie Spencer rode his NR500 to a
first-place finish in a five-lap heat race held at Laguna Seca in California,
which doubled as the qualifying round for an international race. It was with
these victories that the NR500s were established as contenders in the ultimate
challenge: to win a World GP race.
It was, however, still quite premature to assume that victory in a World GP
event was theirs for the taking. That was too high a mountain to climb. After
Katayama's thirteenth place finish at the first Austrian Grand Prix in April
1981, the riders continued to retire from subsequent races. The 1981 season
ended without any point total for the Honda team.
Hence, the promise to become the world champion within three years was broken.
The NR Block had found itself at the crossroads of victory and defeat, survival
and abandonment
Source
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