Hydraulic Dynamometer Disadvantages
|The hydraulic dyno, while useful, has many disadvantages. One being that a hydraulic dyno has to be calibrated from time to time. This increases the chances for the dyno to be out of tune. If the dyno is out of tune, so are your numbers. Power numbers can be skewed by calibration "mistakes" to make things look much more impressive - just be aware that it happens.|
Due to the resistance applied to the vehicle through the rollers, the hydraulic dyno is harder on a vehicle than an inertia dyno. People do make careless mistakes, and motors do pop on dynos from time to time - though it is not always the tuners fault. Just be aware of what you are doing - it is no different from romping on the car on the street, you're still going to be the one to foot the bill if something snaps.
The next disadvantage of the hydraulic dynamometer is the fact that most them have dual rollers. This lends itself to traction problems. Single roller applications are superior - period.
Hydraulic dynos are not as reliable for genuine accuracy. They have a margin of error caused by having several moving parts. They are great for tuning - but for actual horsepower numbers, they are more likely to be inaccurate than an inertial dyno.