Which technician correctly describes the capabilities of chassis dynos and engine dynos?

• A. Technician B
• B. Technician A
• C. Both
• D. Neither

Answer: (B)

Understanding how each dynamometer measures power clarifies why Technician A’s description is correct. A chassis dyno tests the car as a whole on rollers, measuring wheel horsepower and thus the power that actually makes it to the wheels, including drivetrain losses from the transmission, differential, and tires. An engine dyno isolates the engine and measures its output at the crank, providing engine horsepower before any drivetrain losses. Technician A correctly distinguishes the two: one setup reflects real-world wheel power with losses accounted for, while the other shows the engine’s raw power output independent of the drivetrain. If someone suggested both dynos measure the exact same thing or that drivetrain losses aren’t involved, that would misstate their differing purposes.