Logging the data received from the dynamometer

On old-fashioned dynamometers, the operator or the observer had to manually record the simultaneous readings on paper. Nowadays, most dynamometers replace the observer’s notes with computerized devices that acquire and store the data. Because of the very loud noise generated by the dynamometer and the engine, a performance test is stressful to anyone who’s watching it. In these given conditions, it is very difficult to manually record all the data. A reliable computerized data acquisition system is considered to be indispensable today among engine builders and testers. Nowadays it is possible to buy recording, control, and playback capabilities in a palm sized package, that many years ago would have cost a lot more and would have had the size of a refrigerator. An appropriate computerized data acquisition system must have a very fast sampling rate. For obtaining quality data, you will need at least 100 samples, of all sensor channels, per second (100Hz). A 200Hz logging rate or more is even better. It is important to remember that between spark plug firings there is a drop in torque and rpm that can be measured. The crankshaft is accelerated right after combustion occurs and afterwards it slows down until the plug will fire one more time. It is not possible to detect these rapid highs and lows when you are driving on the track or on the road, but the dynamometer will. Therefore, a 200 Hz logging rate for your data acquisition system should do the trick, as well as an appropriate dynamometer. However, if you sample at only 50Hz, you should consider that you are recording a single torque and rpm sample every other revolution. From time to time, a series of samples will synchronize with the firings of the plugs, and sometimes the data samples will fall in synch with some lower power compression strokes. If you are using a fast and reliable acquisition system that read each cycle multiple times, then the data captured can be used to average out the given phenomenon. Averaging the data is a very important step in data acquisition. At this point, while experienced dynamometer operators see an identical power curve in both graphs, inexperienced dyno operators expect to see a smooth, clear line. The reason why the ability to average and dampen the data is essential for the acquisition system is that you don’t have to deal with so many printings. For instance, at 100Hz you're getting 1000 lines of data for even a ten-second dynamometer pull. You might choose not to search for any small changes in dozens of pages of data every time you want to prepare another run. Averaging both eliminates transient noise and produces clear printouts, and thus it is very useful in the process of logging the data from the dynamometer.

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Tips on choosing appropriate dynamometers

In order to set up a drag car or bike for peak performance, using loads of boost / nitrous or other modifications, the best thing to have is a suitable inertial chassis dynamometer. It needs to have big diameter clean drums, with a very good grip. Dual rollers are not appropriate in this case, so don’t use them! The dynamometer should have powerful fans and airflow and an experienced operator. A braked system is simply unsuitable for an application like this. The dyno itself, along with plug readings, and experience would be the best way to set the car / bike up. Gas analyzers are useless in these situations. If your aim is to set up a stock or mildly tuned cars / bikes fuel injection system, or set up a carburetor systems jetting or ignition properly, you should find a decent braked system, maybe with twin rollers and with a good gas analyzer. This is the best way to set up this kind of vehicles. You should use this kind of dyno tools if you are working on stock or mildly tuned car for fault finding, or for a health check. To obtain the accurate power curve picture of a vehicle, you should put on an inertial dynamometer. In order to buy one for yourself, you should consider the above, decide what kind of work you mainly want your dyno for, and choose accordingly. An important thing to remember is that inertial dynos may be cheaper, but they are more difficult to control (you cannot hold RPM steady on an inertial dynamometer). However, no matter what type of dynamometer you select, controlling the test conditions is vital to getting usable data. It's not enough for the dynamometer equipment itself to be accurate; you have to know that the engine's output is not being skewed by improper dynamometer procedures. In order to prepare your car or bike for a dynamometer testing session, you should consider some of the following: You should check oil level, being careful not to overfill. If necessary, perform oil and filter change first. Make sure the air filter is clean. Check coolant level. Check for coolant leaks visually Check tires for correct pressures and healthy condition, especially if it’s a seriously powerful vehicle, as grip may be a problem. Add enough fuel. If you use nitrous, water injection, make sure these are all topped up! Make sure it has correctly gapped healthy plugs. That's basically all you need to do. Dynamometer testing is no worse for your car than a bit of fast motorway driving, and in some cases even safer for your engine!

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Issues regarding the use of dynamometers

A dynamometer is basically a tool to deliver an effective comparison or analysis of an engine output or performance. Dynamometers are a lagging indicator, which means the dyno only tells you what has occurred during the dyno run or test period. After you have applied your best engine building skills, the dyno serves the purpose of evaluating the engine's capabilities at a specified moment in time. A dynamometer mainly measures Horse Power (usually at the crank shaft but in the case of a chassis dyno, Horse Power is only measured at the rear axle), torque, RPM range over which the engine was tested, temperature and air flow (volume and velocity of the air that ventilates the engine). Some dynamometers also measure noise levels of exhaust and intake manifold pressure, fuel flow, BSFC (the measured fuel flow in pounds per hour divided by the horsepower), and pressures such as oil pressure when appropriate. Top racers own a dyno, as it is a very powerful tool. It provides valuable information about the performance of engines, transposed in a set of graphs. As dynamometers measure engine output, isolate and quantify the metrics of horse power and torque, they are very useful for elaborate performance tests. In preparation for performing a dyno test there are certain metrics that you should have or should obtain prior to planning the test. These include the minimum horsepower, the gear ratio if you are not attaching the water break to the output shaft of the motor. A good dyno allows the user to enter today's environmental or altitude conditions. When reporting, the software provides the correction factors so that each day is measured as though it were the same as the last time that the engine was tested or to a set baseline so that you always achieve a set comparison. Dynamometers are very handy and useful, but they are a very expensive piece of equipment. Many of them are also extremely noisy, even when they are running on small motors. The exhaust is caustic and therefore, dynos should be used only in properly ventilated areas. Before investing in a dynamometer, certain aspects should be considered, such as the size of the working space, the possibility of storing volatile fuels, or the access to certain utilities such as proper water supply for the water brakes. A computer and a color printer are also necessary for recording and monitoring the way the engine performs. When the requirements are met, all it takes is ambition, dedication and investing the right amount of time for making refinements and adjustments.

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Improve your car’s performance by using dynamometers

The dynamometer is a device used to measure mechanical force, power and torque produced by an engine. Its inventor, Charles Babbage, is also known as the “Father of Computing. There are basically two types of dynamometers: the first one is bolted directly to an engine, and it’s called engine dyno, while the second type of dynamometer can measure power and torque without removing the engine from the frame of the vehicle, and it’s known as a chassis dyno. An engine dynamometer measures power and torque directly from the engine's crankshaft (or flywheel), when the engine is removed from the vehicle. These dynos don’t take in consideration power losses in the drive train, such as the gearbox, transmission or differential. A chassis dynamometer measures power from the engine directly through the wheels. The vehicle is parked on rollers and the output is measured. These dynos can be fixed or portable. The dynamometer works by applying various loads on the engine and by measuring the engine's ability to move the load. It is connected to a computer which uses mathematics to calculate the output of the engine. The engine is run from idle to its maximum RPM and the output is measured and interpreted on a graphic. Nearly all aspects of engine operation can be measured during a dyno run. Generally, dynamometers are useful in the development and refinement of modern day engine technology. The concept is to use a dyno to measure and compare power transfer at different points on a vehicle, thus allowing the engine or drive train to be altered, in order to get a more efficient power transfer. For example, if an engine dynamo shows that a particular engine achieves 400 N·m (300 lbf·ft) of torque, and a chassis dynamo shows only 350 N·m (260 lbf·ft), it means that in order to recover the power loss, the drive train should be inspected and improved for maximum efficiency. Dynamometers are typically expensive pieces of equipment, reserved for certain fields that rely on them for a particular purpose. They are very handy, as they can diagnose the entire way a car is functioning, but they are sometimes unaffordable.

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Examining the dynamometer data

After you have performed your desired dynamometer tests, you need to take a look at the information you received. If you have a manual recording system you should calculate and transform the torque and rpm readings into horsepower numbers. If you've got a manual electronic data collection the next step will be to print out the data.

On personal computer equipped dynamometers you should name the new data file and enter all the relevant data about the test run you have ended.

There are software packages for your dynamometers that grant you the possibility of entering virtually any parameter you want in certain windows. This is very handy, as you can store important information in a structured data base, making it more accessible. If you don’t own a system equipped with sensors that capture the weather conditions you should write them down as soon as you finish the dynamometer tests.

It is very important to choose an appropriate output report format for reviewing the dynamometer’s data. When you examine the data received from you dyno, you should discard any information gathered during periods of rapid rpm change. You should instead concentrate on the ranges where the engine maintains a stable number of rotations for at least a few consecutive seconds.

Another important step is to average the data received from the dynamometer. Even numbers with some inertial errors can still produce valuable information after they have been averaged.

If you observe any unusual numbers in your results, you have probably made some mistakes when you chose the tachometer pulse settings. Or, if horsepower is a lot smaller than you expected it to be, you should check if the throttle was wide open during the test. You should also remember about the problem of exhaust being reabsorbed into the intake system. Perform another pull, following the same procedures as the first dynamometer test, making sure you everything is checked and working properly. Remember to warm up the engine before you begin the test. On the second run, you shouldn’t make any significant parameter changes, and concentrate on repeatability instead. In fact, you are really testing the repeatability of your actions and the stability of your engine, since the dynamometer did not change between runs.

Whenever possible, when chasing small improvements, you should retest the engine in its baseline state. This additional real-time check will spare you a great deal of time in the more important and longer runs.

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Does dynamometer testing damage the car?

There is no actual proof that dynamometer testing might damage the car in any certain way.

While performing tests, dynos don’t interfere with the engines performance and more importantly, don’t do any damage to it.
Some of the things that may cause damage to engines are over-revving, excessive heating, shock loading or incorrect fuel or ignition settings.
If however your engine malfunctions after performing a dynamometer test, it’s almost certain that the testing, if properly done, wasn’t the cause of the damage.

It is more likely to damage your engine when you drive your car on the road than when you test it by the means of a dynamometer under controlled artificial conditions. You should always make sure that the dyno operator is a trained professional and that the dynamometer has an appropriate cooling system.
A 60 centimeter diameter fan is appropriate for a power run. It will prevent the vehicle from overheating.

However, you should keep in mind that dynamometer testing and setting up race cars and bikes require more controlled testing conditions. A bike or car that heats up after a few hours testing suffers from heat soak into the transmission, bodywork, engine block, oil, and so on. This interferes with the amount of power produced, and influences the accuracy and the objectivity of the performance test.
To make sure everything will go smoothly while performing your tests on engines, you actually need a wind tunnel in which you should manipulate your dynamometer. When you are driving on the road at full power there is a lot of fresh air that surrounds and cools the entire vehicle, and you should do your best to recreate some of these natural conditions when you perform your tests.

If your dynamometer or the place you go to in order to get your car or bike dyno tested does not have suitable working conditions or lacks an appropriate cooling system, it is not advised to perform any tests.
The problem concerning the damage done by dynamometers on the tires is more debatable. Tire manufacturers recommend dynamometer owners to replace tires after every test performed. They claim that the tires design is not intended for purposes like dynamometer testing and say that the heat or tire deformation could damage the interior structure. Due to these facts, they strongly recommend replacing the tires after testing.

However, this should be done more as a precaution, and if the tires are rather new, well designed dynamometers should not damage them. Just to make sure that everything is in order, remember to always check the tires condition after every test you perform.

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All The Things You Need To Know About Engine Dynamometers

The most professional devices that can measure an engine's power and torque are the engine dynamometers. They are used by the engine manufacturers themselves.

In order to perform the measurements on the engine (this is done before the engine in mounted into the chassis), the engine is connected to the dynamometer with a shaft. Afterwards, the engine is ignited, and it is set to run at a constant speed, and the torque that is applied to the dynamometer is exactly the engine's torque. The results of these measurements are quite accurate and there are no losses because of friction.

The new-generation dynamometers are connected to computers and they are very easy to handle and operate. They can almost perfectly simulate racing and normal driving conditions.
When driving on the road, there are a few factors that may modify the way an engine acts and the power it produces. Among these there's the air's temperature, level of humidity and also its pressure. These can be taken into consideration when testing an engine with a dynamometer, with the help of some formulas the power that an engine can give can be calculated under several types of meteorological conditions, so how the power modifies when the air pressure drops for example can be easily calculated.
Real-life conditions can be simulated by increasing the temperature at which the dynamometer tests are performed, because the engine is heating up as it runs.

Anyway, it mustn't be forgotten that once the engine is installed into the chassis it will connect to the drivetrain, and this plus a few more things will make an important part of the power to be absorbed, so the readings from an engine dynamometer will be a little different. To measure the power of the dynamometer 'at the wheels' a chassis dynamometer is required.

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