Cummins N14 STC, Celect, Celect Plus – Service Manual 014-002   Engine Testing (Chassis Dynamometer)

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

Because of driveline inefficiencies and engine-driven accessories, the rated horsepower will be reduced by approximately:

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

The net horsepower available is called wheel horsepower.

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

The following are general safety precautions to be observed while operating the chassis dynamometer:

Use tires that have more than 160 kilometers [100 miles] 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  The “tie down” chains must have slack to prevent damage to the chassis dynamometer.

Carefully position the vehicle onto the rollers.

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

WARNING  Diesel exhaust contains carbon monoxide, a deadly poison. Make sure all exhaust gases are vented to the fresh outside air.

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.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

CAUTION  Do not add cold coolant to a hot engine. This can cause engine casting damage. Allow the engine to cool to below 50°C [120°F] before adding coolant.

Check the engine coolant level to make sure it is filled to the correct level.

Check the engine lubricating oil level to make sure it is filled to the correct level.

Use a known source of “good” quality number 2 diesel fuel. This is very important since 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 gallon (liter, etc.).

To correctly monitor engine performance, record the following parameters. To limit dynamometer operating time, instrument the engine to make as many checks as possible.

Check the engine speed rpm with a verified tachometer.

Check the fuel pressure

Check the fuel rate using fuel measuring device, Part Number 3376375.

Check the fuel temperature if needed to check the fuel rate.

Check the fuel inlet restriction.

Check the fuel drain line restriction.

Check the intake manifold pressure.

Check the intake air restriction.

Check the exhaust restriction.

Check the coolant temperature.

Check the engine blowby.

Check the lubricating oil pressure.

Check the coolant pressure.

Check the inlet manifold air temperature.

Check the turbocharger air inlet temperature.

Check the oil temperature.

Use digital optical tachometer, Part Number 3377462, to check and verify engine speed.

Pressure gauge, Part Number ST-435-6, is included with snap rail pressure gauge, Part Number 3375932.

Measure the fuel pressure. Install the pressure gauge, Part Number ST-435-6, or the pressure gauge in the fuel measuring device, Part Number 3376375, to the fitting on the fuel shutoff valve.

Use fuel measuring device, Part Number 3376375, to measure the rate of fuel consumption.

Connect the fuel return hose from the engine to the fuel measuring device (A).

Connect the fuel inlet hose to the fuel filter inlet (B).

Connect the return hose from the device (C) to the fuel tank.

Connect the fuel inlet hose from the device to the fuel tank suction line (D).

Adjust the fuel rate to compensate for temperature variation if required.

Inlet Fuel Temperature

Do not measure fuel inlet restriction with the fuel measuring device installed. This will not measure the inlet restriction of the vehicle’s supply plumbing.

Measure the fuel inlet restriction. Install a vacuum gauge, Part Number ST-434, between the fuel filter and the gear pump inlet.

The gauge will not measure the correct vacuum if the gauge is not held at the same level as the gear pump.

Hold the gauge at the same level as the gear pump.

NOTE: On CELECT™ and CELECT™ Plus it is not necessary to operate the engine to maximum horsepower—only to high idle.

Operate the engine at maximum horsepower rpm on STC engines.

Observe the reading on the gauge.

Fuel Inlet Restriction CELECT™ and CELECT™ Plus

Fuel Inlet Restriction STC Engines

Correct the restriction or replace the fuel filter.

Do not measure fuel drain line restriction with the fuel measuring device installed. This will not measure the drain line restriction of the vehicle’s return plumbing.

Use pressure gauge, Part Number ST-1273, to measure fuel drain line restriction.

The gauge will not measure the correct pressure if the gauge is not held at the same level as the connection.

Hold the gauge at the same level as the connection.

NOTE: On CELECT™ and CELECT™ Plus it is not necessary to operate the engine to maximum horsepower—only to high idle.

Operate the engine at maximum horsepower rpm on STC engines.

Observe the reading on the gauge.

Fuel Drain Line Restriction CELECT™ and CELECT™ Plus

Fuel Drain Line Restriction STC Engines

Measure the intake manifold pressure (turbocharger boost). Install pressure gauge, Part Number ST-1273, in the intake manifold as shown.

Observe the reading on the pressure gauge.

When operating an engine on a chassis dynamometer, follow these steps for best results and safe operation.

For CELECT™ and CELECT™ Plus engines, lock the cooling fan in the “ON” mode. This can be done by installing a jumper across the temperature switch or by supplying shop air to the control valve. Refer to the fan drive manufacturer for the recommended procedure.

Monitor the intake manifold air temperature using INSITE™ in the monitor mode, or install Fluke digital thermometer, Part Number 3822666, and thermocouple wire kit, Part Number 3822988, into the intake manifold.

The intake manifold air temperature must not exceed the maximum allowable temperature. The engine protection system will disrupt performance if the temperatures exceed this level. Maintain intake manifold air temperature at the nominal level or below during chassis dynamometer operation.

Intake Manifold Air Temperature

If the intake manifold temperature exceeds 77°C [170°F], shut off the engine. Allow the engine to cool.

Inspect the charge air cooler fins for obstructions to the air flow.

Check the fan drive. Make sure the fan is locked in the “ON” mode.

Remove any obstructions such as a winterfront or debris. Manually lock the shutters in the “OPEN” position if equipped.

Inspect the dynamometer room for adequate supply of suitably cool or outside air. Make sure that dynamometer room recirculation is not an issue.

Resume the test.

Lock the cooling fan in the “ON” mode. This can be done by installing a jumper across the temperature switch or by supplying shop air to the control valve. Refer to the fan drive manufacturer for the recommended procedure.

Remove any obstructions to the air flow across the radiator such as a winterfront. Manually lock the shutters in the “OPEN” position, if equipped.

Install a Fluke digital thermometer, Part Number 3822666, and attach thermocouple wire kit, Part Number 3822988, into the intake manifold. Monitor the intake manifold temperature. The temperature must not exceed 77°C [170°F].

If the intake manifold temperature exceeds the above limits, shut off the engine. Allow the engine to cool.

Inspect the radiator fins for obstructions to the air flow. Check the fan drive to make sure it is locked in the “ON” mode.

Resume the test.

Measure the intake pressure drop across the charge air cooler.

This test can be done with a mercury manometer or two separate gauges, Part Number ST-1273. If two gauges are being used, calibrate both gauges on a common pressure source at 206 kPa [30 PSI] to ensure consistency.

Install one pressure gauge, Part Number ST-1273, into the fitting in the turbocharger compressor outlet elbow. Install the other pressure gauge into the fitting in the intake manifold.

Charge Air Cooler Restriction

When measuring the pressure drop, operate a dynamometer at the rpm that delivers the maximum horsepower of engine tested. Engine speed will be 1600 to 1700 rpm on most engines.

The gauge adapter must be installed at a 90 degree angle to the air flow in a straight section of pipe at a minimum of one pipe diameter before the turbocharger.

Measure the inlet air restriction. Install the vacuum gauge, Part Number ST-434, or a manometer in the intake air piping.

Operate the engine at maximum horsepower rpm and advertised horsepower.

Observe the reading on the gauge or manometer.

Intake Air Restriction

The gauge adapter must be installed near the turbocharger in a straight section of pipe at the turbine outlet.

Measure the exhaust air restriction. Install the vacuum gauge, Part Number ST-1273, or a manometer in the exhaust air piping.

Operate the engine at maximum horsepower rpm and advertised horsepower.

Observe the gauge or manometer.

Exhaust Air Restriction

Measure the engine crankcase pressure.

Use blowby checking tool, Part Number 3375150, and water manometer, Part Number ST-1111-3.

Install a plug into the crankcase breather vent tube.

Remove the “bottle stopper” oil filler cap and install the blowby checking tool, Part Number 3375150.

Install the water manometer to the blowby checking tool. Observe the engine blowby.

Engine blowby must not exceed the following specifications:

Use pressure gauge, Part Number 3375275, to measure lubricating oil pressure.

Install the pressure gauge to the main oil rifle and observe the oil pressure.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

All pressure measurements are made at 1800 rpm with the engine loaded or unloaded and the coolant pressure cap removed. Removal of the pressure cap eliminates the effect the coolant temperature has on the block pressure at the time of testing.

Remove the pressure cap.

Use coolant pressure/temperature/flow analyzer kit, Part Number 3822994, to measure engine coolant pressure.

Connect the analyzer to the high pressure manifold.

Coolant Pressure at High Pressure Manifold

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

An alternate location to measure the coolant pressure is the rocker housing water manifold.

All pressure measurements are made at 1800 rpm with the engine loaded or unloaded and the coolant pressure cap removed. Removal of the pressure cap eliminates the effect the coolant temperature has on the block pressure at the time of testing.

Remove the pressure cap.

Use coolant pressure/temperature/flow analyzer kit, Part Number 3822994, to measure engine coolant pressure.

Connect the analyzer to the high pressure manifold.

Connect the analyzer to the rocker housing water manifold.

Coolant Pressure at Rocker Housing Water Manifold