The performance of an engine installed in on-highway vehicles can be tested on a chassis dynamometer.
NOTE: Because of drive line efficiency and engine-driven accessories, the engine horsepower when measured at
the rear wheels will be reduced by approximately:
โข 20 percent for single-axle vehicles
โข 25 percent for tandem-axle vehicles
โข 35 percent for recreational vehicles.
NOTE: These percentages are used for engine run-in only and are not to be used as absolute figures.
Follow all of the OEM’s safety precautions before installing or operating a vehicle on a chassis dynamometer. Failure to do so can cause damage to the vehicle and/or cause personal injury.
Low-profile tires are more sensitive to heat than bias-ply tires. Excessive operating time at full load can damage the tires due to overheating. Check the tire manufacturer’s recommendations for the maximum allowable chassis dynamometer operating time.
While operating the chassis dynamometer, follow the general safety precautions listed below:
โข Use tires that have more than 160 km [99 mi] of use.
Do not use new tires.
โข Do not use recapped tires or tires of different sizes or designs.
โข Make sure the tires are inflated to the manufacturer’s specifications.
โข Remove all rocks or other materials from the treads of the tires that will be rotating on the dynamometer rollers.
โข Make sure there is correct overhead clearance for exhaust stacks, air deflectors, or other attachments above the cab.
Carefully position the vehicle on the rollers.
Attach the tie-down chains to the rear of the vehicle.
Place wheel chocks in front of the front tires.
Adjust the vehicle and dynamometer room exhaust system to make sure all the exhaust gases are removed
from the room.
Refer to the chassis dynamometer and vehicle manufacturer’s recommendations and specifications for testing procedures.
Check the engine coolant level to make sure it is filled to the proper level. Refer to Procedure 008-018 in Section 8.
Check the engine lubricating oil level to make sure it is filled to the proper level. Refer to Procedure 007-043 in
Section 7.
Verify the fuel supply tanks are filled with a known good quality number 2 diesel fuel.
NOTE: Number 1 diesel fuels, along with most other alternate fuels, are lighter (lower specific gravity, higher
API gravity) than number 2 diesel fuel. The lighter the fuel, the lower the energy content (BTU) per liter [gallon].
