Dynapack FAQs

How does the Dynapack work?

The theory of operation, and the implementation of that theory, is actually fairly simple. It took several years and a lot of hard work however, to make it as simple as it is today. The hub of the vehicle is directly attached to a hydraulic absorption unit. We can apply a variable but precise load - all the way up to a hydraulic lock if we needed to. Simultaneously we are monitoring load and measuring the hub RPM, so we can determine the amount of work being performed. It sounds easy until you realize that all of these calculations are very complex and are happening very quickly. Add to this, all of the data logging functions and real-time full-color graphics that are also being calculated, and you begin to realize that what appears to be simple is actually very complex. Being the best is never easy.

We use hydraulics. We do not use inertia, we do not use air, we do not use eddy currents, and we do not use friction. Hydraulics are incredibly powerful, yet precise. We have total control of the axle. Literally. Want to hold a steady RPM? We can hold an axle RPM (within 3 rpm) for a stable engine at any power level - all the way up to the rated maximum torque capacity of the dyno for as long a period of time as you'd like. If the software allowed it, we could stop the engine within one revolution of the crankshaft. Obviously, you would not want to do this, and our software prevents it, but it gives you an idea of just how much power and control we have over the axle.

Our Dynapack controls the car - not the other way around.


What does a Dynopack package consist of?

The major components are:

Power Absorption Units

Each Package is supplied with two in a two-wheel-drive configuration, and four in a four wheel-drive configuration. Each unit is supported by wheels to allow easy movement around the shop area. The hydraulic pumps are mounted on a pivot that automatically compensates for camber or an uneven floor. There are data cables that connect to the main controller, and fittings to attach water hoses for cooling.

Hub Adapters

Four and five lug adapters are provided as standard equipment. These adapters are attached directly to the axle in the same manner as the vehicle's wheel. The adapters use a sliding washer design that is self-centering and, when properly installed, keeps the runout of the shaft to a minimum.


A cabinet houses the computer, printer, Backup UPS, and controller unit. The top of the cabinet has a platform for the monitor, keyboard, and mouse. The cabinet features toolbox style wheels for easy movement. The cabinet occupies a floor space of approximately twenty-four inches square.


Housed in a tower-style computer case, the controller performs the electrical control functions for the power absorption units. A data cable connects the controller to the power absorption units.


The purpose built PC allows the Dynapack software to operate in Microsoft Windows, and operates with simple combinations of mouse and keyboard commands. All data can be saved and recalled for viewing at a later date, and data can be imported in other programs such as Notepad or Excel for other statistical analysis.


An A4 cut sheet colour printer is provided for full color printing of statistical data and graphs.


How is a Dynapack different?

The first and most obvious difference is the elimination of the tyre to roller interface on a conventional roller dyno. The Dynapack eliminates this variable by using a hub adapter that provides direct coupling to our Power Absorption Units. There can be no tyre slip, no rolling resistance, and no chance of the vehicle coming off of the rollers at high speeds. Notice that we call this a variable. Sometimes it may be a problem area, other times it may not. Tyire temperature, tyre pressure, tyre traction, etc. are all variables that can change not only from run to run, but during the run as well.

Throw an unknown variable like this into the equation and your data has now become subject to a potentially high margin of error. It is obviously better if this can be eliminated - which is what we have done.

What you end up with on a roller is a giant, heavy flywheel attached to your engine. The inertia is such that just trying to accelerate the mass of the roller is a substantial load for the engine.

How do you think that your measurements will be affected by being subjected to this large heavy flywheel phenomenon? Will small fluctuations in power delivery be easily noticeable? In a word, no. The flywheel effect tends to take small rapid fluctuations and smooth them right out. This is great if you want your power curve to look like a smooth pretty line, but it doesn't give you much insight into what is really occurring. What if you eliminated the flywheel effect? Whilst every spinning mass has some inertia, when compared to the total mass of the wheels, tires, rollers, and other associated hardware in a roller dyno, the inertia in the Dynapack is practically zero. This allows us to precisely measure and display tiny rapid pulses and oddities that you may not have ever seen before.

Another benefit of having virtually zero inertia is the ability to change the rate of acceleration at will. In many simulations, you may want to make the vehicle accelerate at a different rate to simulate a specific condition. With a few simple keystrokes, we can allow the vehicle to accelerate very quickly, very slowly, or anywhere you'd like in between. Because of the lack of inertia and the total control we have over the axle speed, we give you choices. And as you know, choices are good!

This makes Dynapack an outstanding choice in chassis dynamometers whilst establishing new industry standards.

The above information is courtesy of International Dynamometers Ltd, the makers of Dynapack. An Adobe PDF document of this information is available for download from their website www.dynapack.com

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