Who is correct regarding the dynamometer test?

• A. Technician B is correct; there is no load applied.
• B. Both technicians are incorrect; the test is idle only.
• C. The test is irrelevant to driving conditions.
• D. Technician A is correct; the dynamometer test applies a load to simulate actual driving conditions.

Answer: (D)

Dynamometer testing uses controlled resistance to mimic the road load the vehicle experiences during driving. By applying a load with the rollers, the engine experiences real torque and power demands as it goes through a drive cycle, so emissions are measured under conditions close to how the vehicle actually operates. That’s why Technician A’s view is correct: the test applies a load to simulate actual driving conditions.

Saying there’s no load, that the test is idle only, or that it’s irrelevant to driving conditions misses the purpose of the drive-cycle test. The whole point is to reproduce real-world operating conditions so emissions readings reflect what happens on the road, not just at idle.