How many revolutions does a cube contain?

Torque speed power

1. Single cylinders have the best pulling powerA subjective impression of the single pilots that 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 suggest more “punch” in terms of acoustics and vibrations.2. Single and twin cylinders are less easy to turn

At least if you relate it to the total displacement. A 1000cc four-cylinder is basically made up of four 250cc units. The engine can rev up as fast as the mechanical components of the individual single cylinder allow. In the case of a two-cylinder with a total displacement of one liter, the individual displacement is logically 500 cm3, and it does not achieve such high speeds.

In the case of large individual cubic capacities, the maximum speed is limited not only by the mechanics but also by the gas exchange. Huge cylinders are naturally more difficult to fill, and the combustion is not so favorable due to the limited flame speed. A multi-cylinder is therefore fundamentally superior to a single-cylinder with the same displacement.

3. 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, there is another very crucial component: the gear ratio. Large-displacement naked bikes, for example, are not geared to high top speed, because nobody drives 250 km / h without a fairing.

The overall translation can be correspondingly short. This in turn increases the speed level in all gears; The motorcycle not only appears more dynamic, it actually accelerates better with a comparable torque curve - because more speed or more power is available. 2Wheels determines torque values ​​in the last gear from 60 km / h. A Yamaha Vmax is already turning 2400 rpm, while the crankshaft of a long-geared Suzuki GSX 1400 only rotates at 1800 rpm and therefore has significantly worse cards in a direct comparison.

4. 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 crank drive, which would at some point disassemble itself due to the high inertia, this is, to a decisive extent, the valve drive. 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 some modern designs use 40 percent lighter titanium instead of steel. On the other hand, a good filling requires a lot of valve area. Therefore it makes sense to distribute the area over several valves. Four- or five-valve engines are more speed-resistant than comparable two-valve engines.

5. Letting it spin is unhealthyOnly partially true. Fifteen or twenty years ago, engines weren't that advanced in terms of materials and construction. Back then, more feeling was required from the driver, especially since there used to be no limiter to put a stop to wild rev 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.6. Power and torque have nothing to do with each otherTotally wrong. Both are even directly linked to one another, namely via the speed. The associated formula is M = 9549 x P / n (M in Nm, P in kW, n in 1 / min). At a certain speed, the same torque always results, 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.7. High speeds require strong dimensions On the contrary: a lot of torque puts the greatest strain on the entire mechanics of the drive train. Because at low speeds, the torque curve is more irregular due to the large time intervals between the work cycles; for the peaks, the gearbox and clutch in particular have to be dimensioned powerfully. One wonders how small the clutch is on a Formula 1 engine that develops 900 hp at 18,000 rpm. 8. A linear increase in performance works bestExactly the other way around: 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, above which the V2 gains power. When accelerating, subjective perception is less influenced by absolute values ​​than by the increase in performance. A motorcycle with a linear performance curve initially looks less spectacular, even if it always has more power everywhere.
9. 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.