11 50-16

1

11 50-16

SUBJECT

DATE

Diagnostic Test - Power Verification With Chassis Dynamometer

November 2016

Additions, Revisions, or Updates
Publication Number / Title

Platform

Section Title

DDC-SVC-MAN-0193

GHG17 DD
Platform
Medium
Duty

Power Verification with
Chassis Dynamometer

DDC-SVC-MAN-0191

GHG17 DD
Platform
Heavy Duty

Power Verification with
Chassis Dynamometer

DDC-SVC-MAN-0084

EPA07/10G
HG14 DD
Platform
Heavy Duty

Power Verification with
Chassis Dynamometer

Change

Updated diagnostic procedures, changes to the rpm range.

All information subject to change without notice.

11 50-16

Copyright © 2016 DETROIT DIESEL CORPORATION

3

2 Power Verification with Chassis Dynamometer

2

Power Verification with Chassis Dynamometer

The chassis dynamometer is a device for applying specific loads to a vehicle to determine if the vehicle will perform to
published specifications and to permit a physical inspection for leaks of any kind. It can be used for detecting improper tuneup, misfiring fuel injectors, low compression, and other malfunctions.
Chassis Dynamometer Test and Run-in Procedure
For safe and accurate dynamometer readings, the chassis dynamometer room must be properly ventilated.
WARNING: ENGINE EXHAUST
To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area.
Engine exhaust is toxic.

To avoid injury before starting and running the engine, ensure the vehicle is parked on a level
surface, parking brake is set, and the wheels are blocked.

If a vehicle is tested on a dynamometer located in an area without proper ventilation, the engine will be subject to high
ambient air temperatures. High air inlet temperatures can result in false low power readings on the dynamometer.
To help ensure accurate horsepower readings, the dynamometer room should have a ceiling-mounted fan with an 850 to 1133
m³ /min (30,000 to 40,000 ft³ /min) capacity. This will provide proper ventilation of exhaust gases and heat radiated by the
operating engine.
Chassis Dynamometer Test and Run-in Procedure
The function of the dynamometer is to absorb and measure the engine output after it has been transmitted through the vehicle
transmission and driveline to the drive tires.
The vehicle is connected to the dynamometer through the roller absorption unit. The load on the vehicle may be varied from
zero to maximum by decreasing or increasing the resistance in the unit. The amount of power absorbed in a water brake-type
dynamometer, as an example, is governed by the volume of fluid within the working system. The fluid offers resistance to a
rotating motion. By controlling the volume of water in the absorption unit, the load may be increased or decreased as
required.
The following are some tips to remember in preparing the vehicle before the dynamometer run and during the actual testing:
•
•
•
•
•
•
•
•
•
•
•

4

Follow all applicable safety procedures from the chassis dynamometer manufacturer.
Observe the air intake duct and charge air fan shrouding to identify misalignments. Correct as necessary.
Make sure the differential lock is ON.
Make sure the radiator/charge air cooler system fan(s) are locked ON.
If the vehicle is equipped with anti-lock brakes (ABS), disable the ABS controller by unplugging it or removing its power
fuse/breaker.
Instrument the engine for fuel pressure, air inlet restriction, exhaust backpressure, and crankcase pressure, and note these
readings during the dynamometer run.
Make sure the vehicle hood is down and locked into its normal position.
Make sure the engine is fully warmed up before placing the vehicle on the dynamometer. Both oil and coolant temperature
should be at least 82°C (180°F).
When loading the vehicle on the dynamometer, make sure the vehicle is positioned onto the rollers as straight as possible.
For direct engine cooling, Detroit™ recommends the use of a 368 m³ /min (13,000 ft³ /min) or greater capacity barrel-type
ram air fan. This should be portable so that it can be conveniently placed three to five feet (approximately one to two
meters) in front of the truck and aimed directly at the charge air cooler. This is especially important at high altitudes.
During high ambient temperature conditions 32°C (90°F), it may also be necessary to use a water spray mist fan in front of
the vehicle to prevent overheating.
All information subject to change without notice.

Copyright © 2016 DETROIT DIESEL CORPORATION 11 50-16

11 50-16
• Running the dynamometer in manual mode instead of automatic mode allows for maximum control of the test process and
may result in more consistent test results.
• During the horsepower test, make sure percent engine load and torque limiting factor are 100% by monitoring them with a
computer equipped with DiagnosticLink.
• Select a transmission gear with a 1:1 gear ratio during the horsepower test.
• Take horsepower reading at peak torque and peak horse power rpm. Stabilize at rated speed for at least one minute before
taking a final horsepower reading. Compare the recorded horsepower to the appropriate minimum horsepower table for the
particular rating.
• Note that vehicles with automatic transmissions (i.e. equipped with torque converters) will have slightly lower minimum
horsepower values than those with manual transmissions (with no torque converters).

All information subject to change without notice.

11 50-16

Copyright © 2016 DETROIT DIESEL CORPORATION

5

3 Power Verification With Chassis Dynamometer

3

Power Verification With Chassis Dynamometer

The chassis dynamometer is a device for applying specific loads to a vehicle to determine if the vehicle will perform to
published specifications and to permit a physical inspection for leaks of any kind. It can be used for detecting improper tuneup, misfiring fuel injectors, low compression, and other malfunctions.
Chassis Dynamometer Room Ventilation Recommendations
For safe and accurate dynamometer readings, the chassis dynamometer room must be properly ventilated.
WARNING: ENGINE EXHAUST
To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area.
Engine exhaust is toxic.

To avoid injury before starting and running the engine, ensure the vehicle is parked on a level
surface, parking brake is set, and the wheels are blocked.

If a vehicle is tested on a dynamometer located in an area without proper ventilation, the engine will be subject to high
ambient air temperatures. High air inlet temperatures can result in false low power readings on the dynamometer.
To help ensure accurate horsepower readings, the dynamometer room should have a ceiling-mounted fan with an 850 to 1133
m³ /min (30,000 to 40,000 ft³ /min) capacity. This will provide proper ventilation of exhaust gases and heat radiated by the
operating engine.
Chassis Dynamometer Test and Run-in Procedure
The function of the dynamometer is to absorb and measure the engine output after it has been transmitted through the vehicle
transmission and driveline to the drive tires.
The vehicle is connected to the dynamometer through the roller absorption unit. The load on the vehicle may be varied from
zero to maximum by decreasing or increasing the resistance in the unit. The amount of power absorbed in a water brake-type
dynamometer, as an example, is governed by the volume of fluid within the working system. The fluid offers resistance to a
rotating motion. By controlling the volume of water in the absorption unit, the load may be increased or decreased as
required.
The following are some tips to remember in preparing the vehicle before the dynamometer run and during the actual testing:
• Follow all applicable safety procedures from the chassis dynamometer manufacturer.
• Observe the air intake duct and charge air fan shrouding to identify misalignments. Correct as necessary.
• Make sure the differential lock is ON.
• Make sure the radiator/charge air cooler system fan(s) are locked ON.
• If the vehicle is equipped with anti-lock brakes (ABS), disable the ABS controller by unplugging it or removing its power
fuse/breaker.
• Instrument the engine for fuel pressure, air inlet restriction, exhaust backpressure, and crankcase pressure, and note these
readings during the dynamometer run.
• Make sure the vehicle hood is down and locked into its normal position.
• Make sure the engine is fully warmed up before placing the vehicle on the dynamometer. Both oil and coolant temperature
should be at least 82°C (180°F).
• When loading the vehicle on the dynamometer, make sure the vehicle is positioned onto the rollers as straight as possible.
• For direct engine cooling, Detroit™ recommends the use of a 368 m³/min (13,000 ft³/min) or greater capacity barrel-type
ram air fan. This should be portable so that it can be conveniently placed three to five feet (approximately one to two
meters) in front of the truck and aimed directly at the charge air cooler. This is especially important at high altitudes.
• During high ambient temperature conditions 32°C (90°F), it may also be necessary to use a water spray mist fan in front of
the vehicle to prevent overheating.
6

All information subject to change without notice.

Copyright © 2016 DETROIT DIESEL CORPORATION 11 50-16

11 50-16
• Running the dynamometer in manual mode instead of automatic mode allows for maximum control of the test process and
may result in more consistent test results.
• During the horsepower test, make sure percent engine load and torque limiting factor are 100% by monitoring them with a
computer equipped with DiagnosticLink.
• Select a transmission gear with a 1:1 gear ratio during the horsepower test.
• Take horsepower reading at peak torque and peak horse power rpm. Stabilize at rated speed for at least one minute before
taking a final horsepower reading. Compare the recorded horsepower to the appropriate minimum horsepower table for the
particular rating.
• Note that "Minimum Acceptable Wheel Horse Power" information is for vehicles with manual transmissions. Vehicles
with automatic transmissions (i.e. equipped with torque converters) will have slightly lower minimum horsepower values
than those listed. Refer to section "Minimum Acceptable Wheel Horsepower".

All information subject to change without notice.

11 50-16

Copyright © 2016 DETROIT DIESEL CORPORATION

7

4 Power Verification With Chassis Dynamometer

4

Power Verification With Chassis Dynamometer

The chassis dynamometer is a device for applying specific loads to a vehicle to determine if the vehicle will perform to
published specifications and to permit a physical inspection for leaks of any kind. It is an excellent method for detecting
improper tune-up, misfiring fuel injectors, low compression, and other malfunctions.
Chassis Dynamometer Room Ventilation Recommendations
For safe and accurate dynamometer readings, the chassis dynamometer room must be properly ventilated.
WARNING: ENGINE EXHAUST
To avoid injury from inhaling engine exhaust, always operate the engine in a well-ventilated area.
Engine exhaust is toxic.

To avoid injury before starting and running the engine, ensure the vehicle is parked on a level
surface, parking brake is set, and the wheels are blocked.

If a vehicle is tested on a dynamometer located in an area without proper ventilation, the engine will be subject to high
ambient air temperatures. High air inlet temperatures can result in false low power readings on the dynamometer.
To help ensure accurate horsepower readings, the dynamometer room should have a ceiling-mounted fan with a 850 to 1133
m³ /min (30,000 to 40,000 ft³ /min) capacity. This will provide proper ventilation of exhaust gases and heat radiated by the
operating engine.
For direct engine cooling, Detroit™ recommends the use of a 368 m³ /min (13,000 ft³ /min) or greater capacity barrel-type
ram air fan. This should be portable so that it can be conveniently placed three to five feet (approximately one to two meters)
in front of the truck and aimed directly at the radiator/charge air cooler package.
Chassis Dynamometer Test and Run-in Procedure
The function of the dynamometer is to absorb and measure the engine output after it has been transmitted through the vehicle
transmission and driveline to the drive tires.
The vehicle is connected to dynamometer through the roller absorption unit. The load on the vehicle may be varied from zero
to maximum by decreasing or increasing the resistance in the unit. The amount of power absorbed in a water brake type
dynamometer, as an example, is governed by the volume of fluid within the working system. The fluid offers resistance to a
rotating motion. By controlling the volume of water in the absorption unit, the load may be increased or decreased as
required.
The following are some tips to remember in preparing the vehicle before the dynamometer run and during the actual testing:
• Follow all applicable safety procedures from the chassis dynamometer manufacturer.
• Observe the air intake duct and charge air fan shrouding to identify misalignments. Correct as necessary.
• Make sure the differential lock is ON.
• Make sure the radiator/charge air cooler system fan(s) are locked ON.
• If the vehicle is equipped with anti-lock brakes (ABS), disable the ABS controller by unplugging it or removing its power
fuse/breaker.
• Instrument the engine for fuel pressure, air inlet restriction, exhaust backpressure, and crankcase pressure, and note these
readings during the dynamometer run.
• Make sure the vehicle hood is down and locked into its normal position.
• Make sure the engine is fully warmed up before placing the vehicle on the dynamometer. Both oil and coolant temperature
should be at least 82° C (180° F).
• When loading the vehicle on the dynamometer, make sure the vehicle is positioned onto the rollers as straight as possible.

8

All information subject to change without notice.

Copyright © 2016 DETROIT DIESEL CORPORATION 11 50-16

11 50-16
• For direct engine cooling, Detroit™ recommends the use of a 368 m³ /min (13,000 ft³ /min) or greater capacity barrel-type
ram air fan. This should be portable so that it can be conveniently placed three to five feet (approximately one to two
meters) in front of the truck and aimed directly at the charge air cooler. This is especially important at high altitudes.
• During high ambient temperature conditions 32°C (90°F), it may also be necessary to use a water spray mist fan in front of
the vehicle to prevent overheating
• Running the dynamometer in manual mode instead of automatic mode allows for maximum control of the test process and
may result in more consistent test results.
• During the horsepower test, make sure percent engine load and torque limiting factor are 100% by monitoring them with a
computer equipped with DiagnosticLink.
• Select a transmission gear with a 1:1 gear ratio during the horsepower test.
• Take horsepower reading at peak torque and peak horse power rpm. Stabilize at rated speed for at least one minute before
taking a final horsepower reading. Compare the recorded horsepower to the appropriate minimum horsepower table for the
particular rating.
• Note that "Minimum Acceptable Wheel Horse Power" information is for vehicles with manual transmissions. Vehicles
with automatic transmissions (i.e. equipped with torque converters) will have slightly lower minimum horsepower values
than those listed. Refer to section "Minimum Acceptable Wheel Horsepower".

All information subject to change without notice.

11 50-16

Copyright © 2016 DETROIT DIESEL CORPORATION

9