Dynamometer Basics – What You Need to Know
What is a dynamometer and how does it work?
For chassis or engine applications, a dynamometer is a device designed to create a load to duplicate various speed (RPM) and torque (Nm or lb-ft) requirements. From this data, power (HP or kW) can be calculated. This in turn provides a snapshot of the chassis or engine performance for comparison to the manufacturer’s specifications. Typically a dynamometer gives the operator the ability to vary the load applied to the unit under test to mimic specific requirements.
In chassis dynamometer applications the entire drivetrain can be tested simultaneously. The vehicle is anchored to the floor and the drive wheels are placed on rollers. A chassis dynamometer:
- Tests every rotating portion of the drivetrain
- Confirms the power and torque provided by the engine
- Can aid in the evaluation of performance as well as noise or safety issues
- Can simulate a real world application of the equipment
Another major benefit to chassis dyno testing is the potential elimination of road testing. Road testing takes time and can incur costs if a breakdown or accident occurs. Chassis dynamometers typically create loads using an eddy current (EC) or water brake load device. See the next question below for more information on EC and water brake design.
An engine dynamometer is a device used to test an engine that has been removed from a vehicle, ship, generator, or any other piece of equipment powered by an internal combustion engine. The purpose is to confirm performance before the engine is installed back in the equipment. Engine dynamometers can help facilities troubleshoot by determining when an engine is overheating, or by identifying intermittent performance and sensor issues. They also verify the quality of builds, rebuilds, or repairs in a controlled environment before vehicles are put into use.
Engine dynamometers are coupled to the engine under test via a drive or Cardan shaft. Engines are mounted to rolling carts and can be loaded on the cart prior to movement into the dyno room. Typically, engine dynamometers create loads using a water brake, EC or alternating current (AC) design.
- Water brakes are designed to test engines rated up to 7,500 kW or 10,000 HP
- EC units are designed for lower power engines (less than 400 HP)
- AC designs can accommodate a wide range of applications (10 HP to 5,000 HP) and offer exceptional natural (transient) response
Dyno test stands are used to verify the quality of power shift and automatic transmissions, as well as torque converters and hydraulic pumps, motors, cylinders, and valves. Testing a transmission before it is installed into a vehicle helps operators:
- Check and set shift points
- Test loaded or unloaded, full and closed throttle upshift and downshift
- Measure output torque
- Locate leakage
- Check noise and vibration
- Monitor flow, pressure, and temperature
What are the various types of dynamometers?
Dynamometers are classified by the method of creating a load.
- Water Brake – Water momentum transfer is used to create a load on the engine or vehicle being tested with the absorbed power heating water. Water brake dynamometers are ideal for higher power engine dynamometers with options ranging from 350 to 10,000 HP. These dynos are the most cost effective technology for larger internal combustion engines and electric motors.
- Eddy Current (EC) Brake – An electrically controlled, air-cooled brake, the EC creates load by inducing a magnetic field in a rotating disc. The rotating disc produces heat that is dissipated in air or with water. Power Test uses EC brakes for absorption in lower power applications and makes engine dynamometers rated up to 250 HP. We also use EC brakes on a large range of chassis dynamometers for vehicle testing.
- Alternating Current (AC) Regenerative – AC dynamometers create a load and can return power to the electrical grid through variable frequency regenerative power electronics. Where permitted, the operator of an AC dynamometer can receive payment (or credit) from the utility for the returned power. These dynos allow for fast transient testing with the ability to simulate the forces on an engine while a vehicle is rolling downhill or control the transient test patterns in emissions test cycles. AC regenerative technology are used on engine dynamometers ranging from 10 HP to 5,000 HP, as well as chassis dynamometers requiring transient or road-load control.
Why test with a dynamometer?
Dyno testing is essential if you are a manufacturer or service technician and want to:
- Address engine performance and durability before installation
- Conduct a controlled break-in of a newly rebuilt engine
- Identify a problem without risking a breakdown on the road
- Test a vehicle without the need for a Commercial Driver License
- Reduce warranty or return for service after a rebuild or repair
Dyno testing also is essential if you are purchasing new or used equipment and want to confirm:
- Proof of quality
- Manufacturer specifications are met
What are the benefits of owning a dyno versus taking your equipment to a testing facility?
Like any outsourced service, you need to account for the facility’s availability, pricing and level of expertise in your work order or production schedule. With an in-house dynamometer, you have full control over the quality and expediency of testing. By doing so, you instill confidence in your customers that you have taken steps to ensure they receive the best possible product.
If you are consistently testing, the dynamometer will pay for itself before becoming its own revenue generator for your business. Your Power Test sales representative can share our Payback Calculator with you to determine if dyno ownership makes financial sense for you.