Performance measurement test bench for motorcycle tests

Table of contents

Performance measurement test bench for motorcycle tests
markus-jahn.com

Performance measurement test bench for motorcycle tests

Performance measurement test bench for motorcycle tests

Performance measurement test bench for motorcycle tests

Performance measurement test bench for motorcycle tests

9 pictures

Performance measurement test bench for motorcycle tests
markus-jahn.com

1/9
Every test machine has to go through this: whether like here with the PS-TunerGP or on the editorial test bench, performance measurement is mandatory.

Performance measurement test bench for motorcycle tests
markus-jahn.com

2/9
… Nothing works here without hearing protection.

Performance measurement test bench for motorcycle tests
markus-jahn.com

3/9
Deafening noise: the drive roars, the fresh air blowers whistle, the suction device roars …

Performance measurement test bench for motorcycle tests
MOTORCYCLE

4/9
Small formula collection.

Performance measurement test bench for motorcycle tests
archive

5/9
Developing mappings means a lot of test bench work. Especially useful for tuned bikes.

Performance measurement test bench for motorcycle tests
MOTORCYCLE

6/9
As standard diagrams we usually show the power on the crankshaft (diagram 01) and the torque (03). The lower curve in diagram 02 shows the power loss. It is added to the upper curve (rear wheel power).
For this particular comparison, we superimposed the curves of the Kawasaki Versys 1000 (green) and the Yamaha MT-09 (red). Both machines have a similar peak performance, but differ significantly in terms of displacement. They also play in a different weight league.

Performance measurement test bench for motorcycle tests
MOTORCYCLE

7/9
In diagrams 01 and 03 you can clearly see the motor superiority of the Kawasaki up to the maximum output. With a displacement excess of over 23 percent (1043 to 847 cubic), this is not a big surprise.

Performance measurement test bench for motorcycle tests
MOTORCYCLE

8/9
In terms of tractive power in third gear (04), the green one is still ahead, but it is already closer. The pulling force is the force that acts on the rear wheel. In contrast to the conventional diagrams, the total gear ratio (primary, secondary and gear ratio) is included in the tensile force. The Yamaha has a slightly shorter translation than the Kawasaki.

Performance measurement test bench for motorcycle tests
MOTORCYCLE

9/9
Diagram 05 shows the acceleration. A purely arithmetical value without driving resistance (rolling and air resistance). This value also takes the vehicle weight into account and stands for the dynamics that the driver feels. Lo and behold: suddenly the MT-09 is ahead. At 192 kilos, the Yam is a whopping 63 kilos lighter than the Versys (255 kilos).

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Performance measurement test bench for motorcycle tests

Background test bench measurements for motorcycle tests
This is how performance measurement works

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Clamp the bike on the test stand roller, turn the tap to the stop, is the power measurement finished? Determining the power and torque of motorcycles is not that easy.

Volkmar Jacob

05/12/2015

Deafening noise pervades the room. The drive roars its soul from the engine block, and the two fresh air blowers whistle in the highest tones. In addition, the exhaust device for the exhaust roars. Nothing works here without hearing protection. We are on our test bench, where every test machine goes through the same procedure: determining power and torque. These values ​​appear regularly in the booklet as curves in a diagram. But how exactly does the performance measurement work??

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Background test bench measurements for motorcycle tests
This is how performance measurement works

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Rear wheel performance

In simple terms, the system measures how fast a roller driven by the rear wheel accelerates. To do this, it records the time in which the roller builds up which speed. From the acceleration, the computer calculates the torque and, from this, the rear wheel power, taking into account the mass moment of inertia of the roller. If you want to know exactly how this works, read the last section. So that the computer also spits out how much power is present at which speed, the tester taps the ignition or speed signal on the bike. When measuring, we always chase the motors into the limiter in order to record the maximum speed.

Power on the crankshaft

But how do you get from it to power on the crankshaft? The manufacturers indicate this (higher) value in their data, and we show it in the diagrams. The crankshaft power cannot be measured, only calculated. It takes two steps to do this. First, the test bench determines what is known as the loss or frictional power. It arises in the drive train between the crankshaft and the rear wheel. It includes the secondary drive (pinion, chain, sprocket), the gearbox and the clutch. Tires also cost performance – very soft more, very hard less. The test bench calculates the power loss as soon as the disengaged motorcycle is allowed to coast for a while. This value is added to the rear wheel power, and you already know the power at the clutch. Now pack just two percent of this value on top, and the crankshaft power is ready. Example: A machine has 200 HP on the clutch. 204 HP are then applied to the crankshaft. 

Road tires instead of rough ones

Why? In most engines there is a transmission between the clutch and the crankshaft – another performance hog. An EU directive puts this loss of performance at two percent. 

In order to keep the power loss as low as possible, the testers always pay attention to a well-lubricated chain, correct sag and the right tire pressure (approx. 2.5 bar). Coarse tires (sport enduro, crosser) are being replaced by road tires. 

Do you fancy formulas and equations? Here you go!

If you have made it this far, you will surely appreciate a few formulas and equations. Loyal readers may recall that we plowed this subject a few years ago. Here again some expertise to freshen up. 

As mentioned at the beginning, the test stand records the acceleration of the roll. For this he needs two values: firstly the speed difference of the individual measurements (∆v, pronounced: Delta-Vau) and secondly their time difference (∆t, pronounced Delta-Te). The acceleration (symbol: a) is calculated as follows: a = ∆v / ∆t. Example: If the roller increases its rotation speed every second by four revolutions / second (in the first second it rotates four times, in the second eight times, in the third twelve times, etc.), this results in an acceleration of 4 / s². However, acceleration alone does not get us any further, we also need the mass moment of inertia (symbol: Q) of the test stand roller. To put it roughly, this physical quantity expresses how much a rigid body defends itself from being set into rotation or being braked from such a rotation. The mass moment of inertia is calculated from the mass (m) of the roller and its radius (r). The following formula applies: Q = m • r² • 0.5. Example: A roll weighing 1000 kilograms has a diameter of 46 centimeters (corresponds to a radius of 23 centimeters, = 0.23 meters). The mass moment of inertia Q is 1000 kg • (0.23 m) ² • 0.5 = 26.45 kg m². 


Performance measurement test bench for motorcycle tests


MOTORCYCLE

Small collection of formulas for determining performance.

The test bench computer uses this value to calculate the torque (symbol: M) with which the roller with the mass moment of inertia Q is accelerated by the amount a. The following applies: M = Q • a. For our example this means: 

M = 26.45 kg m² • 4 / s² = 105.8 kg m² / s². The unit for force (Newton, N) can also be written as kg m / s². Therefore: 105.8 kg m² / s² correspond exactly to 105.8 Newton meters (Nm). 

From this we can immediately calculate the kW output (symbol: P) at a certain speed (symbol: n). All we need is a constant that converts from revolutions per minute to meters per second. This constant is 60000 / 2π, i.e. approximately 9549. π describes the ratio of the circumference to the diameter and is approximately 3.1415. The following applies: P = n • M / 9549. If the 105.8 Nm are applied at 4450 rpm, for example, the drive at this speed consequently produces 49.3 kW, which equates to 67.1 hp. As is well known, one kW equals 1.36 hp.

Measured and calculated values


Performance measurement test bench for motorcycle tests


MOTORCYCLE

Here we show the diagrams for the power on the crankshaft as well as on the rear wheel.

As standard diagrams we usually show the power on the crankshaft (diagram 01) and the torque (03). For this particular comparison, we superimposed the curves of the Kawasaki Versys 1000 (green) and the Yamaha MT-09 (red). Both machines have a similar peak performance, but differ significantly in terms of displacement.


Performance measurement test bench for motorcycle tests


MOTORCYCLE

Diagram 3

They also play in a different weight league. In diagrams 01 and 03 you can clearly see the motor superiority of the Kawasaki up to the maximum output. With a displacement excess of over 23 percent (1043 to 847 cubic), this is not a big surprise. 


Performance measurement test bench for motorcycle tests


MOTORCYCLE

Diagram 4

In terms of tractive power in third gear (04), the green one is still ahead, but it is already closer. The pulling force is the force that acts on the rear wheel. In contrast to the conventional diagrams, the total gear ratio (primary, secondary and gear ratio) is included in the tensile force. The Yamaha has a slightly shorter translation than the Kawasaki. 


Performance measurement test bench for motorcycle tests


MOTORCYCLE

Diagram 5

Diagram 05 shows the acceleration. A purely arithmetical value without driving resistance (rolling and air resistance). This value also takes the vehicle weight into account and stands for the dynamics that the driver feels. Lo and behold: suddenly the MT-09 is ahead. At 192 kilos, the Yam is a whopping 63 kilos lighter than the Versys (255 kilos). The lower curve in diagram 02 shows the power loss. It is added to the upper curve (rear wheel power). 

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