"The dyno is used to apply a load to the engine to replicate driving the car on the road. As well as being able to apply a load to the engine, the dyno will also be able to measure the torque being produced and from this the engine power can be calculated. Depending how smart or advanced the dyno is, it will also be able to log parameters such as boost pressure and air fuel ratio and provide the tuner with torque and power graphs that can be analysed after a run. From here we can make decisions on what elements in our tune to adjust.

 

The advantage here to the tuner is that the dyno can provide instant and accurate feedback about the progress of their tune. A good dyno should be sensitive enough to show very small changes in torque, like the difference caused by alternator draw when the headlights switch on and off. This makes it easy to tell if we are going the right way with our tuning, and a proper load bearing dyno is essential to correctly calibrate elements such as ignition timing and cam control."

Source article: https://www.hpacademy.com/

What is DYNO