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This article will take an in-depth look at engine dynos.
The article will bring more detail on topics such as:
Principle of Engine Dynos
Types of Engine Dynos
Applications, Benefits & Maintenance of Engine Dynos
And Much More…
Chapter 1: Principle of Engine Dynos
This chapter will discuss what engine dynos are, their design, and their function.
What is an Engine Dyno?
An engine dynamometer is a device used to test an internal combustion engine that has been removed from a car, ship, generator, or any other accessory that uses one. The goal is to verify performance before reinstalling the engine in the equipment.
Engine dynamometers can aid troubleshooting by determining when an engine is overheated, as well as recognizing intermittent performance and sensor faults. They also test the quality of new builds, rebuilds, and repairs in a controlled environment prior to putting them into service.
A drive or cardan shaft connects engine dynamometers to the engine under test. Engines are mounted on rolling carts and can be put onto the cart before being transported to the dyno chamber. Engine dynamometers typically use a water brake, EC, or alternating current (AC) design to generate loads.
Water brakes are used to test engines with a power output of up to 7,500 kW (10,000 HP).
EC units are made for engines with lesser horsepower (less than 400 HP)
AC designs can handle a wide variety of applications (10 HP to 5,000 HP) and have a natural (transient) response that is second to none.
Design of an Engine Dyno
Engine dynos are different, but they all have the same components: an absorption unit or driver, a torque development mechanism, and a torque and rotational speed measurement instrument. The absorber is usually a rotor in some form of enclosure attached to the testing equipment.
Friction, hydraulic fluid, or electromagnetic power are commonly used to generate torque. A load cell or strain gauge is commonly used as the measuring device, however it could alternatively be a weighing scale, such as a crane scale. Note: Load cells, also referred to as load sensors, convert perceived mechanical force into measured mechanical signals.
Engine Dyno Coupling
A coupling is a device that links two shafts at their ends so that power can be transmitted. Couplings connect two pieces of rotating components while permitting some degree of misalignment and or end movement. A coupling can also be a mechanical mechanism that connects the ends of nearby pieces or objects in a broader sense.
Couplings generally do not allow shafts to be disconnected during operation, however, torque-limiting couplings can slip or disconnect if a torque limit is exceeded. Couplings can be chosen, installed, and maintained in such a way that maintenance time and expense are decreased.
Engine Dyno Tachometer
A tachometer is a tool for measuring an engine's rotational speed in revolutions per minute (RPM). Tachometers, both mechanical and electronic, work in different ways. A moving item in the engine or gearbox is connected to the gauge via a flexible cable with a spinning shaft. The rotating shaft inside the instrument regulates the position of a needle that indicates the engine speed.
An electronic tachometer generates electrical pulses at a frequency proportional to engine speed using a magnetic pickup placed near a moving engine part. The meter's circuitry translates the pulse frequency into a digital readout that displays engine RPM.
Engine Dyno Torque Arm
The torque arm is a suspension device that attaches to the rear-drive axle of a rear-wheel-drive vehicle. The car can accelerate in a straight line without moving the back axle, thanks to this arm.
By delivering force to the braking system, this arm also assists the vehicle in braking. This device is also found on an engine dyno and attached to a scale which measures the reactions and displays them.
Engine Dyno Absorption Unit (Rotor)
An absorbing dynamometer simulates a load driven by the prime mover being tested. The dynamometer must be capable of operating at any speed and load, producing any level of torque required by the test.
Absorbing dynamometers are not to be confused with "inertia" dynamometers. Inertia dynamometers compute power simply by measuring the amount of energy necessary to accelerate a known mass drive roller while providing no changeable load to the prime mover. All engine dynamometers are absorbing dynamometers or have absorption units. The operating torque and speed of an absorption dynamometer are usually measured in some way.
The power developed by the prime mover is absorbed by the power absorption unit (PAU) of a dynamometer. The dynamometer absorbs the power and converts it to heat, which dissipates into the ambient air or transfers to cooling water, which also dissipates into the air. Regenerative dynamometers, in which the prime mover drives a DC motor as a generator to generate load, generate excess DC power that can be sent back into the commercial electrical power grid via a DC/AC inverter.
To provide distinct major test kinds, absorption dynamometers can be equipped with two types of control systems which are constant force and constant speed.
Engine Dyno Trunnion Bearings
It is one portion of a rotating joint in mechanical engineering where a shaft (the trunnion) is placed into (and revolves inside) a full or partial cylinder. This connection, which is frequently employed in opposing pairs, enables tight tolerances and strength thanks to the wide surface contact area between the trunnion and the cylinder.
These are self-contained concentric bearings used in airframe engineering to provide fluid movement in a key steering section. The phrase is also applied to the wheel on which a rotating cylinder travels.
Engine Dyno Data Acquisition
A data acquisition system is an integral component of a dynamometer. Typically, the system consists of two units, a commander and workstation, connected by means of an Ethernet cable. The commander is a desktop computer that is operated by windows-based software. This commander issues commands to the workstation, a touch-screen operated unit that is housed in a rugged industrial enclosure.
The workstation operates the throttle control systems and precision load, collects the data, and sends the data to the commander for processing, storing, and analyzing. The success of the workstation, and therefore the data acquisition system’s accuracy, depends on its ability to correctly measure data in the dyno tests.
The precision of its pressure transducers is central to these measurements, which measure the flow of air in the oil pressure, intake manifold, and other fluid pressures. The operator’s interest in different fluid pressures so having the capability to bring in different pressures while running the engine is very important.
How an Engine Dyno Functions
These machines measure the revolutions per minute (RPM) or torque of the flywheel or crankshaft of an engine to determine its horsepower. They get this data by converting the torque force into an electrical signal, which they can then translate into a legible measurement. Separate tests on engines and vehicles can be performed on dynamometers. As a result, they're widely employed in engine rebuilding, as well as diagnostics, design, and production of autos and high-performance vehicles.
How to Dyno Test
The first step is determining the best dynamometer for one's purposes and then properly installing it, before beginning to use the device for horsepower testing. A mild engine that can be run at peak power and that is generally quite reliable is recommended to begin with if possible.
The next step is to warm the engine to operating temperature, applying light loads to the engine occasionally during the warm-up. Then, a full load can be applied gradually onto the engine while simultaneously regulating the rpm using the control valve.
Once at a wide-open throttle the throttle is left there while moving between desired test rpm points with the brake’s load valve. Findings from the dyno test are recorded. After stepping through each rpm point (for a span of time which allows for an accurate reading) the throttle is reduced while also unloading the brake simultaneously so that the engine returns to an idle state. At this point, data collection can be concluded. This is the first dyno test.
It is recommended to go beyond just one test, however; this allows the practice of this process and ensures that the data that has been collected is correct, repeatable and has value to improving the engine’s performance.
The information gathered during the dyno test can be saved and analyzed later to see if the engine's horsepower needs to be improved. It's also worth noting that the process may need to be repeated a few times to get the engine's dyno testing just correct.
Factors to Consider when Choosing an Engine Dyno
The various factors to consider when choosing an engine dyno include:
What is Being Tested?
What exactly are you testing - engines straight from the vehicle or the entire vehicle? If the answer is "vehicles": Are you testing automobiles, motorbikes, trucks, ATVs, go-karts, or a mix of these?
Is a four-wheel-drive dynamometer required, or will a two-wheel-drive dynamometer suffice? Do you prefer an independent or coupled axle?
Do you just want to absorb power or do you want motor capability? The dynamometer is chosen for both engines and vehicles based on the horsepower range, the sort of testing being done, and the cost.
It's essential to realize that horsepower is a computation that reflects the relationship between torque and revolutions per minute (rpm) throughout an engine's operational range. Dynos, like engines, are rated for torque and revolutions per minute.
To choose the appropriate engine dyno, one must first determine the estimated peak torque of each engine to be tested, as well as the rpm at which the torque is created. One will also need to know what the engines' maximum rpm is. The engine manufacturer is usually the source of this information (or designer if it is custom-built). Knowing the sorts of engines that will be tested (gasoline, diesel, etc.), the size of the engine (displacement), and the application in which they are utilized might help make an approximate prediction (trucks, cars, motorcycles, industrial, snowmobile, racing, on-highway, off-road, etc.).
Another thing to think about is the type of engine testing you'll be doing and the parameters involved. You can design a test profile or schedule that includes your engines' typical horsepower and torque ratings at the rpm ranges you expect to see them at. A graph of "Horsepower and Torque vs RPM," often known as a power curve, can then be plotted using those figures.
After you've gathered this data, you can choose a dynamometer that matches those parameters. Each series and model has a unique absorption characteristic and, as a result, a unique power curve that corresponds to its capabilities.
There are three different types of dynamometer testing:
When the engine is permitted to accelerate from a set lower "beginning" rpm to a defined upper "ending" rpm, this is known as an acceleration or sweep test. When a deceleration test begins at a high rpm and concludes at a lower speed, the same approach can be utilized. The dynamometer controls the engine's acceleration and deceleration rates. Sweep tests are frequently used to build an engine's performance or power curve.
The dynamometer will hold the engine or vehicle at a particular speed, torque, or power for a certain period of time during a steady-state test. Stable state testing includes step tests and break-in tests.
The speed of the engine or vehicle, as well as the applied load, fluctuates during the test cycle, which is known as a transient or cyclical test. The difference between a transient and a cyclical test is that a transient test has varying load points whereas a cyclical test has constant values. A drive cycle, which is commonly used in automobile emissions testing, is an example of a transient test. A simulation of a car moving around a lap is an example of a cyclical test. The dynamometer will alter the load on the engine in both circumstances to produce the appropriate results.
Although most dynamometers can perform all three types of testing, some are more suited to a certain type of testing than others. Water brake dynamometers can normally handle any engine and any type of test, but because they are slow to respond to load changes, they aren't ideal for fast transient testing. The inertia of AC dynamometers is often high, which can affect how well they perform in acceleration testing. An AC dynamometer, unlike a water brake or eddy current dynamometer, can realistically model how an engine coasts down when the throttle is dropped.
The price of a dynamometer is a significant consideration. Given that the cost of a data collecting and control system is similar, the power absorption unit is the emphasis. An AC dynamometer is the most versatile and costliest of the three primary types of dynamometers. The key benefit of a motoring dyno is that it absorbs power and drives the engine, providing a more accurate representation of how the vehicle would perform on the road or track. The size of the motor (horsepower rating) and the ancillary equipment required for operation determine the value of a motoring dyno (a drive unit and regenerative device).
The majority of eddy current dynamometers are water cooled and only require a small amount of cold water to operate (an air-cooled eddy current requires no water). The physical size of an eddy current absorber, on the other hand, is proportional to its power absorption capability, which is reflected in the price (the bigger the unit, the more it costs). The greatest power that an eddy current dyno can handle is limited. Eddy current absorbers typically range from 100 to 500 horsepower, but larger models are available.
In comparison to an AC dynamometer, a water brake dynamometer is often more cost effective. At one-fourth the cost, a water brake absorber half the size of an eddy current absorber can often manage three times the horsepower. A water brake absorber, on the other hand, requires water—and sometimes a lot of it. Only a few hundred gallons of water are required for low-power, infrequent use (two or three times per week), and short-duration testing (less than one hour per day).
However, for high-powered engines and extended test days, you'll need a significant volume of water or a complex cooling system, which might drive up the overall cost of the system. The majority of water brake absorbers start at 500 horsepower and increase from there (at a fraction of the cost of a comparable eddy current). When the water supply system is taken into account, however, the whole cost nearly equalizes.
Chapter 2: Types of Engine Dynos
This chapter will discuss the various types of engine dynos.
Eddy Current (EC) Dynos
These types of engine dynos make use of an electromagnetic brake to load an engine. The EC induces a magnetic field in a rotating disc that creates a load. The rotating disc produces heat, which then dissipates in air or with water. In lower applications, the power test makes use of EC brakes for absorption and makes engine dynamometers rated up to 250 HP. EC brakes are also used on a large range of chassis dynamometers for vehicle testing.
The main advantage of water cooled EC engine dynos is their precise and rapid control of load. The load can be adjusted from zero to 100% in a few milliseconds by varying the energy supplied to the coil and the adjustment can be very precise also. The disadvantage of eddy current dynos is that they are typically 40 to 60% more expensive than water brake dynos and their dynamic range is not broad as well. This means that EC current dynos are typically chosen for more specialized testing.
AC Motor (Alternating Current) Dynos
These types of dynamometers can create a load and return power to the electrical grid through regenerative power electronics that use variable frequencies. The operator of an AC dyno can receive payment from the utility for the returned power, where permitted.
These types of dynos allow for transient testing that is fast, with the ability to simulate the forces on an engine during the rolling of a vehicle downhill or control the patterns of the transient test in emissions test cycles. AC regenerative technology is utilized on engine dynos with a range of 10 HP – 5,000 HP, and chassis dynos that require transient or road load control.>
Water Brake Dynos
A load is created on the engine or vehicle being tested using water momentum transfer with the absorbed power heating water. These types of dynamometers are ideal for engine dynamometers of a higher power with options that range from 350 to 10,000 HP. These dynos are the technology that is the most cost effective for internal combustion engines and electric motors that are large. They make use of a hydraulic brake that is capable of converting the energy produced by the engine into heat transferred to the water that flows through the dyno.
A side is stationary (stator) and a side that is spinning (rotor), each having pockets that are cup shaped, that are responsible for transferring water from one side to the other. An automatic control valve bolted to the dyno controls the quantity of water in the dynamometer based on the requirements of the test to produce the required load against the engine.
The main advantage of these dynos is that they provide a wide dynamic range meaning one dyno has the capability to test a wide range of engine speeds and engine torques. Water brake dynos are also the most economical type of absorber that can be utilized for dynamic testing making them suitable for a broad range of applications from testing internal combustion engines to electric motors.
Engine Dyno vs. Chassis Dyno
This section will contrast an engine dyno to a chassis dyno.
Engine Dyno Basics
This type of dyno calculates the power output by measuring the magnitude of the force (torque) required to hold a spinning engine at a set speed (rpm) directly. The software of the dyno then calculates the horsepower. This is done based on the torque figure and engine rpm (horsepower = torque x engine speed, divided by 5.252. The dyno consists of a control board that shows torque readouts, water temperature, oil temperature and pressure, rpm, exhaust temperature, and air/fuel ratio via sensors that are connected to the engine. The engine can be started and run by the dyno operator from the board via a cable-operated lever or electronically, according to the dyno. The engine is mostly stripped of its accessory drive and is fitted with a header and according to the needs of the customer, a full exhaust system.
Since the engine dyno measures torque directly, an engine dynamometer provides you with the most accurate picture of the amount of power that is generated by your engine. Because of that, an engine dynamometer is the most accurate way to do part comparisons or fine-tuning an engine to obtain maximum power. Engine dynos have advantages that include repeatability, well controlled testing conditions, and easy access to the engine for swapping parts and tuning.
Chassis Dyno Basics
While an engine dynamometer measures power directly from the engine, a chassis dyno measures the output of an engine or more accurately the output of the drivetrain at the drive wheels of a vehicle. In the basic form of a chassis dyno, it is composed of a platform with a pair of drums or rollers, power absorption or braking system, and software that is used to calculate power output.
The vehicle to be tested is placed on the dyno with the wheels of its drive on the drums or rollers. Depending on the type of the dyno, the software calculates the output of the torque based on the vehicle’s speed of acceleration of the drum or via a load cell that measures the power that is absorbed by the rollers. The torque value is used to calculate the horsepower. Most of the chassis dyno types can monitor air/fuel ratios and other parameters of the engine.
The claim to fame of the chassis dyno is the ability of measuring power at the drive wheels-the performance of a vehicle in the real world. Tuning changes can be made, as well as test parts to find out the effects on power, just as it’s done with an engine dynamometer, though not as easily. And because there are standard factors for power losses of the engine through the drivetrain, a chassis dyno can offer you a good idea of the efficiency of your drivetrain.
Chapter 3: Applications, Benefits & Maintenance of Engine Dynos
This chapter will discuss the applications, benefits, and maintainability of engine dynos.
Applications of Engine Dynos
The applications of engine dynos include:
Aerospace or aircraft
Chain or belt drives
Benefits of Engine Dynos
Engine dynos offer so many benefits to users. First, they help manufacturers determine their engines power and electric motors before they are released to the market. Engine dynos help pick up on any inefficiencies or performance issues that are capable of causing problems or cost money. These issues include slow power acceleration and faulty brakes.
With the knowledge of these problems, manufacturers can make fine adjustments that are necessary to help them achieve optimum performance as well as safety levels. With improved safety and performance, manufacturers feel more confident and will not have to pay out for repairs or costly recalls. They can also give assurance of the safety of their product to their customers.
Engine dynos also help engines power up and run more efficiently, as well as ultimately contributing to the environment’s health, because if there are more efficient engines there will be less fuel used and emitted. Manufacturers can also test their engines against EPA standards.
Engine dynos are becoming more automated and more advanced all the time. In the continuation of this trend, the degree of errors made by humans decreases while measurement speed and accuracy increase. Engine dynamometers are expected to improve power, safety, efficiency and performance of engines for many more years to come.
Maintenance of Engine Dynos
Considerations in engine dynos maintenance include:
Conduct Service at Recommended Intervals
For increased productivity, the dyno must be maintained at recommended intervals. A manual guide must be used for preventative maintenance. The key personnel must be trained on the use and maintenance of the equipment. Power test’s technical service staff must be utilized for on-site support, calibration, evaluation, maintenance, and repairs.
Water Quality is Critical
Water quality is one of the top priority factors in the longevity of a dyno.
Keep Water Temperatures Cool
Engine dynos can use in excess of 100 gallons of water per minute. If the water going into the dyno is cool, the dynamometer also stays cool, and it will deliver more hours of service. If recirculated water is used, it must be run through a cooling tower to lower its temperatures before sending it through the dyno.
Match Lubrication Maintenance With Run Frequency
Power test engine dynos consist of two different lubrication points: the high speed bearings and the trunnion bearings. Depending on how old the dyno is, the lubrication system is either grease or oil. The owner's manual must be used for application guidance.
Investigate Peculiar Vibration Sounds
Looking for a loose bolt is a common reaction to a vibration sound. But if there is a loose bolt or broken fastener, it could actually be the result of a larger issue. For instance, the failure to properly phase and align a driveshaft can result in vibrations that destroy the driveshaft, dynamometer and/or engine. Adding on the potential to cause bodily harm if the driveshaft reaches its point of failure
Engine dynos, also referred to as engine dynamometers, are devices that are used to test an engine’s internal combustion. They calculate the power output by measuring the magnitude of the force (torque) required to hold a spinning engine at a set speed (rpm) directly. There are different types of engine dynos offering different benefits. For example, the water brake dynamometers which provide a wide dynamic range meaning one dyno can test a wide range of engine speeds and engine torques. However, for maximum performance, the engine dyno must be regularly maintained.
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