Which type of dyno uses hydraulics to add and subtract load through the dyno software?

• A. Inertia
• B. Waterbrake
• C. Hydraulic
• D. Eddy current

Answer: (B)

Load on a dynamometer is often controlled by the braking medium, and the one that uses fluid resistance regulated by software is the waterbrake. In this setup, the engine powers a brake that dissipates energy by forcing water through a brake chamber; the dyno software adjusts valves or flow to change how much water passes, thus adding or subtracting load precisely. Inertia dynos rely on a heavy flywheel’s momentum rather than a hydraulic flow, and eddy current dynos use magnetic resistance controlled by electrical current rather than fluid flow. A hydraulic dyno is a broader term, but the specific, commonly used hydraulic load mechanism controlled via software is the waterbrake, which is why it’s the best answer.