Table of contents
Torque and speed
Torque and speed
Worlds collide when a sports engine is supposed to tease out top performance from a minimal displacement, while a cruiser engine can draw its power from maximum volume. MOTORRAD shows what it looks like inside two completely different representatives.
Gert Thole, Waldemar Schwarz
Let us begin with a chapter that can be dealt with briefly, namely the common features of the engines of
ZX-6R and VN 2000. In terms of top performance, the two engines are not far apart. 118 hp calls Kawasaki for the super sports car, the cruiser with the largest displacement currently on the market should offer 103 hp. But the way in which this achievement comes about could hardly be more different. No wonder if it is generated from 636 cm3 cubic capacity, distributed over four cylinders, the other time from a two-cylinder with 2053 cm3. A good 1000 cm3 are compared to just under 160 cm3 individual cubic capacity. This relation is also reflected
This is reflected in the speed level, the small four-cylinder reaches its performance zenith at 13,000 rpm, the giant V2 only needs 4800 revolutions to let its muscles play to the maximum.
Similar peak performance at completely different speeds, which inevitably results in two fundamentally different torque curves. At 177 Newton meters at 3200 rpm, the VN 2000 more than two and a half times as much torque as with the small row four, which has the maximum
of 67 Nm at 11000 rpm. So on the one hand the athlete who is trained to convert his speed power into dynamics as effectively as possible. On the other hand
the heavy athlete who has trained his muscles to move as much mass as possible.
Two characters who went their separate ways in the presentation
walk. The engine of the ZX-6R works in secret
under a disguise and is trimmed to the strictest diet. The exhibitionistic VN 2000, on the other hand, grows optically with its pounds, loves posing as a bodybuilder, the show in front of an audience. This is reflected in the technology, for example in valve control. Between the actuation of the four valves via camshafts below, long bumpers and forked rocker arms with hydraulic valve clearance compensation on the VN 2000 and direct actuation via two above
Camshafts with bucket tappets on the ZX-6R are worlds apart.
The 600 series is determined by the performance concept, while the 2000 series is based on the technology of American cruiser models. Although the valves of the steam hammer weigh “only” three times as much as the tiny 17 and 19 gram gas exchange organs of the super sports car, the total mass of the oscillating parts of the VN valve train is more than ten times that. Such a valve train prohibits high speeds.
These are already impossible due to the VN crank drive, because its key data overshadows everything that has existed in the motorcycle sector. The 103 millimeter thick pistons cover a unique 123.2 millimeters between top and bottom dead center, making the V2 an extreme long-stroke, next to which even the 101.6 millimeters of the American model from Milwaukee look downright modest. The extremely short-stroke construction of the
ZX-6R with a 68 millimeter bore and 43.8 millimeter stroke. Despite the completely different design, the piston speeds, which are calculated from the stroke and speed, are at a similarly high level for both. The athlete’s pistons slide up and down at 13,000 rpm at 19 m / s, which is amazing
Filigree components of the VN 2000 travel at an average of 19.7 m / s at 4800 revolutions.
It is also surprising that the pistons of the VN 2000, which weigh around one pound, pull their connecting rods with less inertia than the 200 gram counterparts of the super sports car. That explains the almost graceful shape of the long VN connecting rods. A lot of mass always means a lot of inertia, the small ZX-6R pistons can set your crankshaft in rotation much faster. The 636 is as direct and lively as it is fitting for a real athlete. A quick burst of gas? the UN is doing itself first
much more difficult. Because with the rotating masses, the
VN 2000 another record. Together with the alternator rotor and connecting rods, the monstrous crankshaft of the VN 2000 weighs a whopping 24.8 kilograms, around 2.5 times as much as that of the ZX-6R.
The torque plays a special role in the dimensioning of all drive components, especially high peaks at low speeds put an enormous strain on the drive train.
In addition to the already enormous mean values of the torque, it must be taken into account in the case of the VN that it is produced in only two cylinders at very low speeds. This brings more non-uniformity with high peaks when either of the two pots ignites. Accordingly, everything that transmits the torque to the rear wheel must be designed generously. Starting with the inverted tooth chain as the primary drive to the large coupling, which at 8.1 kilograms weighs more than twice the ZX-6R component. Finally, it continues over the lavishly designed five-speed gearbox including countershaft. The complete gear set with countershaft alone is more than twice as heavy on the VN 2000 as on its sporty sister, at 11.7 kilograms. Concessions to comfort provide additional love handles. During the little
Inline four-cylinder already has an acceptable mass balance due to its design, the huge 52-degree V2 requires two balance shafts for proper vibration behavior, and they add another 2.2 kilograms.
So kilogram after kilogram is constantly adding up. The result at the final showdown of the engines on the scales: At 49.6 kilograms, the engine of the ZX-6R shows the state of the art and undercuts the current 1000 super sports engines by around ten kilograms. Unlike the VN 2000, whose propellant rate sets a different record at 136 kilograms. And even proud of it. After all, pounds are not a flaw in cruisers, they are almost part of the agenda. In a real cruiser, weight should be visible and tangible, and mass should become an experience. Therefore, every part that was installed at the UN is powerful and heavy. And since the heavy engine also requires a strong backbone, there is also a lot of chrome-
Accessories and metal parts are attached, Kawasaki states that the VN 2000 weighs an impressive 371 kilograms.
As with the bodybuilders, the VN 2000 wastes a lot of energy on posing, on the show. Outstanding performance cannot be achieved despite the impressive thrust from the lowest engine speeds in view of a power-to-weight ratio of 3.6 kilograms per hp. With the wiry top athlete ZX-6R, whose engine has easy play with 188 kilograms fully fueled, each horsepower only needs 1.6 kilograms of motorcycle
accelerate. She impresses with race instead of mass.
Torque and speed
Stammtisch slogans don’t always hit the mark, but sometimes they hit the spot. MOTORCYCLE explained,
what applies to motorcycle engines and where the
Popular opinion is wrong.
Bikers agree on one thing:
What matters is what comes out at the back. But there is a lot of confusion about how the propulsion comes about. A typical example:
Power and torque have nothing to do with each other
Totally wrong. Both are even directly linked to each other, namely
about the speed. The associated formula is M = 9549 x P / n (M in Nm, P in kW, n in 1 / min). At a
at a certain speed this always results with the same power
same torque, regardless of the engine type, number of cylinders or other factors. A designer can only teach a motor a certain performance characteristic, the torque curve then results automatically.
Four cylinders are not elastic
You have to differentiate between the measured values and the subjective experience. From a metrological point of view, the performance-optimized multi-cylinders are not only on a par with the one or two-cylinder, they are superior. Because the torque of four-cylinder engines is at least as great in the lower speed range, in the upper range it is superior to that of two-cylinder engines with comparable displacement. Which brings us to the next misjudgment:
Single cylinders have the best
A subjective impression of the single-
Pilot who has absolutely nothing to do with reality. Unfortunately, you have to put it so hard: Big singles only seem so powerful to the drivers because they are
acoustically and vibrationally suggest more »punch«.
Single and twin cylinders are less easy to turn
At least when you look at it
Refers to the total displacement. A 1000cc four-cylinder is basically made up of four 250cc units. The engine can turn just as high,
as the mechanical components of the individual single cylinder allow. In the two-cylinder with one
Liters of total displacement, the individual displacement is logically 500 cm3, and that does not create such high speeds. The maximum speed is
in the case of large individual cubic capacities, in addition to the mechanics, also by the
Restricted gas exchange. Huge cylinders are naturally more difficult to fill, and it also runs
Combustion does not decrease so favorably because of the limited flame speed. A multi-cylinder is one
As a result, single-cylinder cylinders of the same displacement are fundamentally superior.
A lot of speed requires little mass
The highest speeds can only be achieved with light engine parts. The mechanical limit is mainly set by the moving masses.
In addition to the crankshaft drive, which would at some point disassemble itself due to the high inertia forces, the valve drive is crucial. Above a certain speed, the valves can no longer follow the cam profiles, then there is an unhealthy rattle, and then collapse. Therefore everything is done to keep the oscillating masses small. You need light valves, which is why 40 percent lighter titanium has recently been used instead of steel. On the other hand, a good filling requires a lot of valve area. It therefore makes sense to distribute the area over several valves. Four- or five-valve engines are more speed-resistant than comparable two-valve engines.
Letting it spin is unhealthy
Only partially true. Before ten,
Twenty years ago the engines were not so well developed in terms of materials and construction, at that time more feeling was required from the driver. Especially since previously none
Limiter put a stop to wild speed orgies. Today, high speeds hardly damage the engines. On the other hand, low speeds and high torque can put enormous strain on the innards of the engine as well as the entire drive train. If the speed drops below a certain level, if the chain whips and hits, the transmission makes unhealthy noises. To make matters worse, the oil supply and cooling work less effectively at low speed.
High speeds require strong dimensions
On the contrary: a lot of torque
puts the greatest strain on the entire mechanics of the drive train. Then
at low speeds, the torque curve is due to the large
The time intervals between the work cycles are more irregular, for the tips
The gearbox and clutch in particular must be dimensioned strongly. One wonders how small the clutch is on a Formula 1 engine that develops 900 hp at 18,000 rpm.
A linear increase in performance works best
Exactly the other way round: A torque hole often means that the increase is felt all the more spectacular afterwards. Example: An Aprilia RSV mille treats itself to a slack in the middle area and lays it on top
the V2 with power. When accelerating, the subjective perception becomes less due to absolute values
shaped, but rather by the increase in performance. A motorcycle with a linear performance curve initially looks less spectacular, even if it always has more power everywhere.
The draft miracle
Pulling definitely has something to do with the torque curve, nothing works without power in the basement. When accelerating from low speeds, however, another, very crucial component has an impact: the gear ratio. Large displacement
Naked bikes, for example, are not geared towards high top speed, because nobody drives 250 km / h without a fairing. The last gear can be translated accordingly briefly. That in turn increases the speed level in all gears, the motorcycle not only looks more dynamic, it actually accelerates better with a comparable torque curve? because more speed or more power is available. MOTORRAD determines torque values in the last gear from 60 km / h. A Vmax turns at least 2400 rpm, while the crankshaft of a long-geared GSX 1400 only rotates at 1800 rpm and thus has significantly worse cards in a direct comparison.
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