B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 014-002   Engine Testing (Chassis Dynamometer)

The performance of an engine installed in on-highway vehicles can be tested on a chassis dynamometer.

NOTE: Due to driveline efficiency and engine-driven accessories, the engine horsepower when measured at the rear wheels will be reduced by approximately:

• 20 percent for single-axle vehicles
• 25 percent for tandem-axle vehicles.

NOTE: These percentages are used for engine run-in
only and are
not to be used as absolute figures.

Follow the general safety precautions listed below while operating the chassis dynamometer:

• Use tires that have more than 160 km [100 mi] on them. Do
  not use new tires.
• Do
  not use recapped tires or tires of different sizes or designs.

• Make sure the tires are inflated to the manufacturer’s specifications.
• Remove all rocks or other material from the tread of all tires that will be rotating on the dynamometer rollers.

• Make sure there is correct overhead clearance for exhaust stacks, air deflectors, or other attachments above the cab.

CAUTION  To prevent damage to the chassis dynamometer, there must be some slack in the tension of the tie-down chains.

Carefully position the vehicle on the rollers.

Attach the tie-down chains to the rear of the vehicle, and put wheel chocks in front of the front wheels.

Adjust the vehicle and dynamometer room exhaust system to make sure all exhaust gases are removed from the room.

Refer to the chassis dynamometer and vehicle manufacturer’s recommendations and specifications for testing procedures.

The following procedure assumes that the lubricating oil and fuel supply systems are correct, the dipstick calibrated, and the engine filled to the correct levels with lubricating oil and coolant during installation of the engine into the chassis. If these systems were
not serviced during installation of the engine,
refer to Procedure 014-006 (Engine Run-In (Engine Dynamometer) in Section 14 for instructions on priming the lubricating oil and the fuel system requirements, and calibrating the dipstick. Refer to the Operation and Maintenance Manual, B5.9G, Bulletin
3666112, or Operation and Maintenance Manual, B5.9LPG, Bulletin
3666213, for instructions on filling the lubricating oil and the cooling systems.

The number of instruments and gauges required to perform a chassis dynamometer test will vary according to the type and the capability of the test equipment used.

To monitor an engine’s performance correctly, record the following parameters:

• Exhaust back pressure
• Lubricating oil pressure (vehicle instrument panel)
• Coolant temperature (vehicle instrument panel)
• Coolant pressure*
• Intake manifold pressure*
• Inlet air restriction*
• Blowby*
• Engine speed (rpm) (vehicle instrument panel)
• Wheel horsepower (hp) (dynamometer controls)
• Fuel supply pressure.

*See the following for the service tools required and the installation locations on the engine.

Measure the coolant pressure at a coolant tap on the exhaust side of the cylinder head.

Pressure Gauge, Part Number ST-1273

Install a pressure gauge, Part Number ST-1273, in the location shown.

Measure the intake manifold pressure (turbocharger boost).

Water Manometer, Part Number ST-1111-3

Vacuum Gauge, Part Number ST-434

Connect a water manometer, Part Number ST-1111-3, to the turbocharger air inlet pipe to test air restriction.

NOTE: The manometer connection
must be installed at a 90-degree angle to the airflow in a straight section of pipe, one pipe diameter before the turbocharger.

NOTE: A vacuum gauge, Part Number ST-434, can be used in place of the water manometer.

Blowby Checking Tool, Part Number 3822476

Measure the blowby by installing blowby checking tool, Part Number 3822476, in the crankcase breather vent. Connect the blowby tool to a water manometer.

Refer to Procedure 014-010 (Crankcase Blowby, Measure) in Section 14 for blowby specifications.

NOTE: Excessive blowby indicates a turbocharger malfunction or an internal engine component malfunction, allowing combustion gases to enter the crankcase.

NOTE: If a sudden increase in blowby occurs or if blowby exceeds the maximum allowable limit during any run-in step, return to the previous step and continue the run-in. If blowby does
not reach an acceptable level, discontinue the run-in and determine the cause.

NOTE: Avoid long idle periods. Operate the engine at low idle
only long enough (3 to 5 minutes) to check for correct lubricating oil pressure and any gas, lubricating oil, water, or air leaks.