The word dynamometer is defined in the dictionary as: Dynamometer (Dy – Na mom e – ter) – any number of devices for force measurement or measurement of mechanical power. The word comes from the Greek (dunamis force) + (metron measurement) and dynamometers might seem more like Greek than anything else until you learn a little something about them.
Dynamometers have been around for ages. Well, almost. Dyno testing didn’t really get off the mark for serious use until Watt decided that horsepower was something to call the power equivalent to horseflesh that was doing the heavy lifting of the day (1780). The first real reference to brake horsepower (as in dyno testing) wasn’t used until about 1822 and the horsepower game hasn’t been the same ever since. Dynos have been part of the more serious scene for engine builders, racers, and engineering groups in the U.S. since about the early to mid-1950s.
Because of the many assumptions of what a dyno can do for you, perhaps it is timely to look more closely at how you should think about dynos as a potential part of your business and how it might really have an effect.
What do you want a dyno for?
If you want to improve your engine building product or to develop a better engine combination, a dynamometer testing program could help you achieve that goal. Whether you buy a dyno and make that large investment or rent dyno time to achieve your goals is a serious decision and worthy of sincere investigation.
What type of dyno: engine or chassis setup?
First of all, none of the devices are inexpensive. The facilities to support them are not cheap. Adequate support personnel are not cheap, either. So if you are looking for a cheap solution to your engine testing needs, the best solution would be to align yourself with a shop that rents dyno time. This type of strategic alliance will assist you to produce better quality control on your engines and also assist in your development cycles as well.
Rental or purchase?
The most common type of dyno that folks think about (if they build engines) is an engine dyno. Ask yourself if you can keep the dyno busy with other than your own work in order to help pay for the thing. Engine dynos today generally cost from a low of $30,000 to about $70,000 of your hard earned dollars. Then you need to consider where you are going to put it. The best solution here is to build a dyno room and that will cost at least another $10,000 to $30,000.
Chassis dynos can generally be kept busier than engine-only dynos. However the facility support is typically more complex (takes more real estate) and perhaps because of that the dyno of your choice will have to have at least another full-time employee in order to properly support the installation so that it can be a money maker for your shop.
The typical engine dyno testing charges from across the country vary from $500 per day to about $1,000 per day, depending on the level of support that is supplied. You can learn a lot about a given engine combination in a day if you plan your testing, tuning and parts swapping carefully. The typical chassis dyno testing charges vary from $30 to $50 per pull to about $200 for a “tuning” session of two hours or so. Labor charges are all over the map and depend on what type of testing is done and what level of tuning support is offered.
Does the manufacturer understand what you need to accomplish with a dyno?
Many of them don’t understand your gut felt passion for doing what you do, but some of them do. You have to ask around and see what others have to say before making the commitment. Complex operations or software doesn’t help you to build a better engine. Look for what can save you time while gaining better information on what you want to accomplish. Ask about service after the sale and how customers are handled. That is a big portion of what you might be getting into.
Planning a Dyno Test
Go with a plan, because wishes won’t work when it comes to testing. Be aware of one thing when you are renting a testing facility or service. You are the boss! Taking suggestions so that your planning is adequate is good, but it is you who is the customer. Because you are going to be paying for the test, try and get the most out of the time and dollars expended.
Talk with the test facility guys before you go to the test session. So that they can help you plan more effectively, find out what parts they expect you to bring to the test session. Bell housing? Headers? Your own shop rags or paper towels? Know before you go. If you have a flat tappet camshaft in the engine, what do they recommend for a break-in procedure? Soft springs need to be changed after break-in? Different rocker ratios after break-in? Remember that you also might be required to re-torque the heads after the cam break-in. All that is before you start in on whatever lists you want to follow in order to begin to tune the engine.
Make a list. The list helps make up the plan. Don’t go into a dyno test session with three carburetors, five manifolds, three camshafts, and two separate ignition systems and expect to get it all done in one day on the dyno. Be realistic and be methodical. Be very rigid about keeping notes and work at creating good documentation of your testing experiences. This process alone (if done well) will help move your racing program forward.
Goals and Objectives
Part of the plan should outline what you want to test and what specific parts you want to test. Sequences are important so that you can get the best bang for your buck. Most testing services start charging and the clock begins when you and your engine or chassis are on site.
If you require a particular fuel, you had better have enough for the tests or you will be paying for down time while waiting on more fuel. The same goes for specific lubricants. If you intend to break-in the camshaft and then change oil, as is the common practice, then you had better have your brand with you. If you don’t, you are still on the test facility’s clock while someone goes for the items that you forgot.
Plan on trying to keep the water temperature, oil temperature and the A/F ratio as controlled as possible. If testing on a chassis dyno, the temperature of the bearings on the dyno, the temperature of the transmission and the temperature of the drive axle should be controlled to as much as possible.
Even the inflation pressure and the temperature of the drive tires are important variables to control if dependable results are the goal. Note that it is a lot easier write this stuff than it is to actually do it. Put in some time in creating a plan that will help you keep focused on the real target of the testing session, which is to gain more useful data to convert to meaningful information. Test first and analyze later.
What about comparing dyno numbers?
Numbers only mean something if you know where the numbers come from. Believe it or not, it can be done. It is actually pretty easy to compare dyno numbers from different facilities if the numbers and arithmetic are done correctly AND if the equipment is properly calibrated.
You know how it is when various folks try to compare the dimensions on a block or a crankshaft or any other engine component. It depends on the skill of the operator and on the calibration of the measuring equipment. If you have ever tried to explain that to a customer, then you have a small taste of the problem with different dyno numbers.
The space allotted here is not nearly enough to address all the details of either dynos or dyno testing, but hopefully you now have a little better understanding of at least some of the things to consider.
Harold Bettes is a dynamometer and flowbench test equipment consultant with more than 35 years of experience in working with these test devices. His private phone number is in many major racing team engineers’ pockets for consulting reference. His company Power Technology Consultants can be reached at www.powertechnologyconsultants.com.