Who the correct Power on the Roller dynamometer first and foremost requires realistic and reproducible information. However, different variables must be included in this calculation. Therefore it is necessary to consider various aspects and to skilfully avoid possible sources of error. Here we explain what you have to pay attention to and how the technology behind the modern dynamometer works.
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- Dynamics of performance measurement
- Old standards meet new technology
- 50.000 cubic meters per hour
- Two different methods for the same measurement
- Crown roll -> less flexing work
- Double roller test stand no less accurate
- Correct measurement: procedure in practice
- Reference values from the street
- Influence by the test driver?
- Engine power: wheel power plus towing power
- Slip: The greatest enemy of measurement
In relation to one dynamometer Two questions arise: What does such a dynamometer actually do? And how does it work? To participate in such an investigation of the Power to participate is the right one Equipment essential - that includes a safety goggles and earplugs. This is not fun! Because the process is not just loud. Due to the high rotational speed of the tires of up to 300 km / h, any stones that may be present can loosen from the profile and create new facial features. And if a tire blows during such a measurement, it is certainly a scenario that no one wants to imagine.
The professionally performed performance measurement has its own drama. Because the full acceleration to the achievable top speed is really heavy depending on the vehicle. means: While the process begins at an initial speed of 50 km / h, the rotation of the tires increases at breakneck speed their maximum raised. It will can not be only increased the speed. As the wheels rotate, the engine revs up and the rollers whirl, the noise level increases rapidly. A combination of whimpering, screeching, yowling, whistling and hissing forces the bystanders to a few meters away to keep from happening.
Depending on the car, a real element of force can be observed on the tension belts or chains that are tensioned to tear. Such a scenario takes around 30 seconds. Then, when rolling out the wheels, the towing capacity determined."back
The current EEC norm was developed for engines that no map had. That's because it dates back to 1980. Environmental factors such as Intake air temperature and Air pressure were very far-reaching back then. That's why it was extrapolated - depending on the location of the test bench. However, the adjustments to such factors are nowadays beyond the Map motors partly done independently.
The software of the engine control unit also uses the Component protection, which Emission and other important variables themselves. The Correction factor ideally be as small as possible. That means - the temperature should be between 20 to 25 degrees in the measuring room. The air pressure, however, depends on the test and his Altitude. Artificial compensation can be used here can not be hergestellt ."back
This is especially true with turbo engines Cooling during the measurement particularly important. This affects the Charge airthat realistically needs to be cooled. Also have to Oil and water cooler be clean and well flown. Air must also flow through the engine compartment, as does the transmission Cooling requirement Has. On Heat build-up increases the intake air temperature, which means that the electronics take less power. Even if all values for the engine are correct, it can happen that the end result not fit. That could be because a too high temperature from Transmission Control Module is reported. The consequence is that the control unit the performance is reduced.
Is the car additional lowered, the cooling is at zero, there none surrounding air arrives. Also Cooling air fan in front of the car are important. Additional Component blowerthat are used by professionals can be used mobile and variably. For example the Intercooling targeted flow. If everything fits, it still has to external environmental factors be factored in, for example Air pressure or the room temperature, Also the Legislative requirements is notable."back
The roller dynamometer relies on wear-free Eddy current brakes. These brakes generate an electromagnetic force on the rollers Counter torque to the wheel force. As a result, the vehicle can be braked and the engine can be loaded. There are two different types of roller dynamometers: on the one hand, the Double roller test bench, on the other hand the Single roller dynamometer. Both are different from each other."back
The so-called is particularly modern Single roller dynamometer. With him, the wheel runs on the Parting or the Knoll a role. This scenario is more realistic and manages with less undesirable loads on the tires and drive train. That works too Power transmission chain better between roller and tire because the temperature of the tire is barely any over 60-70 degrees increases.
The maximum speed of a good single roller dynamometer is around 320 km/h, with a performance between 250 kW and +1.100 kW respectively from 1.500 HP as permanent load per axle. The rollers have a diameter of about 30 inches (0,76 m) and are each with Electric motor and Eddy current brake fitted. The synchronous running of the vehicle axle is ensured. This is done by the machines with sufficient power and a coupling of the roller sets that is electronically controlled."back
The Double roller test bench the wheels are turned between two rollers. It is a support and a brake roller. Its diameter is smaller than that of a crown roll. The wheels are stably guided in a lowered roller prism. However, there are disadvantages to this system.
This is because the rolling behavior of the tires barely with those on the Street adress can be compared to the prevailing conditions. There is a risk of too much here Slip, as modern vehicles are always evolving and stronger become. The subject of roll slip is crucial when it comes to that reproducible measurement of performance goes. In order to minimize the slip, aids must be used on the double roller - for example the car tension down and Spraying the tire or a weighting of the drive axle. Often a few death-defying people sit in the trunk. Despite the higher flexing work, the measurement is no less accurate. This is compensated, namely between the Wheel power measurement and the Power loss measurement."back
Before the measurement, the vehicle is thoroughly on Leak or Leaks checked. The focus is on the tirewho are exposed to high stress due to the measurement. Because they have to Power transfer. That means, Air pressure and camber should consistent so as not to negatively affect the grip on the roller. Other factors also play a role, such as the fuel and its temperature. If it is too hot and has a low octane rating, the measurement can do that influence negatively. In addition, the car should be put to the test the abkühlbecause a hot engine is too uncontrolled Auto-ignition tends. The software for the full load map would be prompted to protect the components To take away performance."back
An extra check on the road makes sense, but is not part of the usual scope of performance measurement. Reference values such as boost pressure and Intake air temperature mittels OBD surface determined for the test run. This ensures that suitable data is used during the measurement. For example, if the intake air temperature while driving is 45 degrees at 200 km / h and medium load, then should similar parameters to be implemented on the test bench. In addition, values for Governing speed, Throttle position and Ignition angle determined. To do this, it is necessary to select the correct test course in which the measurement was made. Is measured in a high gear, whereby the speed level is chosen so that with an acceleration of around 50 km/h can be started. The is suitable for strong vehicles fourth or fifth Gangto move the range from 50 to 240 km / h to cover well.
Video: so better can not be
Next up is the vehicle with Fixing straps or chainsso it's on the roll optimally adjusted is. Then the conditioning. In addition to a test run, the correct positioning of the vehicle is checked and none tension occur. In addition, the Basic parameters again wheelbase and the expected Acceleration performance will be documented."back
A BMW M5 F10 has a ramp value of 2,0 m / s at a strength of from 560 HP. That corresponds to his average acceleration capacity. In addition, the weight value that applies to the rotating mass is preselected. At 19 inch wheels that would be close 80 kg. The measurement takes place in two steps. First the Wheel performance determined via the acceleration. As soon as the speed limit is reached, disengaged, At a automatic transmission will the neutral level inserted. Then the towing capacity determined during roll-out. The selected test course for the wheel power measurement is off two reasons of importance.
Tip: That is what one understands by the Power loss / drag power!
First of all it is necessary that the vehicle is able to do so cleanly from a takeoff speed of around 50 km/h zu accelerate. With the automatic transmission, there is also the fact that each gear has one Minimum speed has that it must be observed. If this is not the case, the transmission shifts automatically back. The second reason is that the maximum speed allowed during the test run in the test bench not exceeded may be. Modern single roller test stands are able to run at a speed of up to 300 km / h get along.
Within the Wheel power measurement the test driver has little leeway to intervene, even if something else is often said. The driver has to accelerate quicklyas soon as the initial speed is present in the test gear. Thereby means Full throttle geben under no circumstances, that the Kick down is triggered, otherwise the transmission shifts down. While the acceleration goes to the end of the speed, the rest is done by the test bench. That's why there is for the examiner while accelerating none Possibilityto influence the outcome."back
While coasting, the test driver would have theoretically the possibility of using the brake to help. That would push the result. However, it is noticeable when the Towing power curve from their parabolic course deviates. Braking into a parallel force and increasing the curve and thus the power, can not. The result would be a atypical curve shapewho on disagreements would indicate.
also: - you add them up Wheel performance and the towing capacity, you get the Power. Because the following applies to power: mass x acceleration x speed. There are both on the test bench and on the vehicle Mass fractions. When measuring, the two are like a sandwich. While the engine drives everything, all are masses a burden for him. The static part is made up of the loads of the brakes on the rollers. This means that the flywheel must also be a dynamic component highly accelerated ."back
The vehicle's drivetrain, together with its rotating components, forms various components on the dynamometer losses. These losses put a strain on the engine during the wheel power measurement. About the towing capacity these dynamic and static losses are determined. It follows from the Addition of the wheel power and the Loss or drag the Power.
Again and again there is confusion due to the terms Wheel and power loss. Contrary to what is often assumed, the measured wheel performance represents can not be the performance on the bike. Because the vehicle as well as the test bench form together one unity. If you take the car away from the test stand, the losses and the mass of the test stand are eliminated. That's why the Wheel performance on the test lower and the towing capacity must be measured and added up.
A modern test bench can take the entire loss measure precisely and reproducibly. The prerequisite for this, however, is that the framework conditions are met. There are many of them. Some depend on test off, others from the Environment and some will mandatory by the legislator the vorgeschrieb.
Slippage is a great enemy of measurement. This arises at sports car and especially at Turbo enginesas soon as the boost pressure builds up. As long as this is in a range of six to eight percent are located, they move within the frame. In addition, there is a precise measurement realistic conditions requires. That means, for example, that a car that is on over 200 km / h is accelerated, must also receive sufficient cooling."back
Of course that had not happened yet!
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