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