Inertia Dynamometer Disadvantages
|The primary fallback of an inertial style dyno is the fact that it cannot measure horsepower at a sustained RPM. You absolutely must be under wide open throttle to get a proper reading. This makes tuning fuel and ignition maps very tedious and difficult, because you don't get any time to monitor the engines behavior at a specific RPM for more than a split second.|
Aside from having to be under load to properly function - the simplicity of the inertia dyno has led many to believe that it is an easy task to make their own. Many of these "DIY" dynos are not accurate at measuring actual horsepower. There is a lot of precise measurement and calculation that must go into the dyno's program initially on an inertial dyno - this is the one and only time the dyno is "calibrated". If something is done incorrectly during this process - the results will be off accordingly.