Testing Engine Output at Exhaust Emissions on Roller Dyno
Testing Engine Output at Exhaust Emissions on Roller Dynamometer
Connection diagram for testers with adapter
001 Digital tester
005 Exhaust probe
006 Opacity analyzer
010 Adapter
011 Trigger clamp
014 Extraction device
015 Test cable with connector
016 9-pin diagnostic socket at TDC pulse generator (021)
017 RI generator
021 TDC pulse generator
Check fluid levels (engine oil, automatic transmission fluid, coolant) and adjust to correct level.
Connect digital tester (001), TDC pulse generator (021) and RI generator (017).
Secure front wheels. Place wheel chocks about 100 mm in front of front wheels.
Check inflation pressure of rear wheels, adjust to specified pressure.
Check contents of trunk, remove any objects which are heavy or sensitive to heat.
Position extraction device (014) behind exhaust pipe.
Switch air conditioner or automatic climate control off.
Warm up engine at part load, selector lever position "3" or third gear, approx. 25 kw, engine oil temperature about 80°C. Do not exceed 120°C.
Cool engine with blower. Direct air flow onto radiator and underside of car (oil sump, exhaust, catalytic converter, tires). Maintain distance of about 1m between blower and car.
Full load output test (see table). Pay attention to barometer reading, coolant temperature and intake air temperature. Refer to notes regarding engine output tests.
Note: Conduct full load test only for as long as necessary for reading the instruments.
Special tools
Instructions regarding engine output test on the roller dynamometer as well as output correction and driving instructions
Engine output test
This test should only be conducted if a complaint is received regarding engine output. The relevant output reference values are minimum outputs and apply to vehicles with power steering. Take into account barometer reading and intake air temperature (see annex). it is good practice to conduct an engine output test after a running-in period of about 5000-8000 km.
Driving Instructions
It is essential to adhere to the following instructions in order to keep the tire stress within permissible limits.
1. Do not drive with winter tires on roller dynamometers. Only warming-up at part load is permissible.
2. Do not inflate the tires of the driving wheels of cars beyond the specified pressure (Owner's Manual).
3. A high axle load on the driven wheels is not permissible.
4. Restrict the driving period to the time absolutely necessary for reading the instruments (about 5 seconds for output test: about 20 seconds for exhaust opacity).
5. Do not exceed a speed of 130 km/h with original tires (120 km/h with SR tires). If the test speed is in excess of 130 km/h, use shop test tires.
6. Adhere to the test instructions and to the following sequence: warming-up - output test - exhaust test at full load, upper part load, lower part load - idle speed - exhaust opacity at idle speed. The full load test (output, exhaust opacity) should be conducted immediately after warming-up so long as the tire temperature is still low as the temperature rises most sharply during these measurements.
Two repeat measurements after adjustment work are permissible. Always maintain an interval (45 minutes) to allow the components to cool down before conducting further measurements.
Note: If the car is fitted with the catalytic converter, the test procedure must be interrupted immediately if combustion faults occur, otherwise damage may result to the catalytic converter.
7. Cool the vehicle with a blower (minimum capacity 15,000 m3/h). Direct the air flow to the radiator and the underside of the car (oil sump, exhaust, catalytic converter, tires). Maintain a distance of about 1 m between blower and car.
Note: The minimum air throughput of 15,000 m3/h is also adequate for cooling cars fitted with the catalytic converter.
Use of the correction table
General
The barometer of the weather station must be set to the atmospheric pressure as indicated by the local meteorological office.
The engine output measured must be corrected with the correction factors.
A distinction is made between 2 correction factors:
altitude correction factor
engine output correction factor
Determining engine output related to normal operating conditions
1. Take the readings of atmospheric pressure, altitude and intake air temperature of the test location on the weather station.
2. Determine engine output on the dynamometer.
3. Take the altitude figure of the test location in the altitude correction table and read off the altitude correction factor.
4. Atmospheric pressure figure of test location minus the altitude correction factor produces the atmospheric pressure (p) in hPa (mbar).
5. Take the calculated atmospheric pressure (p) in the engine output correction table to determine the output correction factor (KH) on the basis of the intake air temperature (t).
6. Take the engine output correction formula to determine engine output related to normal operating conditions as follows:
Engine output correction formula
Ne0 = Ne * KH
Ne0 = output related to normal operating conditions in kw.
Ne = output measured on dynamometer in kw.
KH = correction for intake air temperature, barometer reading at altitude of the test location.
Calculation example far correction table
1. Take the readings of atmospheric pressure, altitude and intake air temperature of the test location on the weather station.
In the example:
Atmospheric pressure of test location = 955 hPa (mbar)
Altitude of test location = 400 m
Intake air temperature of test location = +20°C
2. Determine engine output on the dynamometer = 100 kw
3. Take the altitude figure of the test location = 400 m to obtain an altitude correction factor of 46 hPa (mbar) in the altitude correction table.
4. Atmospheric pressure of test location minus the altitude correction factor produces the atmospheric pressure figure (p):
955 hPa (mbar) - 46 hPa (mbar) = 909 hPa (mbar)
The atmospheric pressure (p) must be rounded in order to insert it in the table. In the example to 910 hPa.
5. On the basis of the atmospheric pressure (p) = 910 hPa, we read off a correction factor (KH) of 1.0787 from the output correction table at an intake air temperature K(t) = 20°C.
6. Engine output related to normal operating conditions is obtained as follows:
Ne0 = Ne X KH
Ne0 = 100kW x 1.0787 = 108kW
Note: The figures for this example are marked in the correction table.
Output on dynamometer:
Ne= 100kW
Atmospheric pressure of test location:
P = 955 hPa (955 mbar)
Intake air temperature of test location:
t= +20°C
Altitude of test location:
400 meters above sea level
Units: hPa = Hecto-Pascal
1 hPa= 1 mbar
1 Pa = 0.01 mbar
Engine output correction on dynamometer for diesel engines In accordance with 80/1269 EC
Altitude correction
If the atmospheric pressure related to sea level is read off (weather station), the following atmospheric pressure in the correction table should be deducted.
Preparing the repair order
Instructions for use of the operation numbers in the various workshop sectors.
Repair order processing
The repair orders should be prepared by the Service Advisor in the response to the customer complaint, taking into account the mileage of the vehicle and any maintenance service which may be due or which was recently performed. The customer complaint should be described precisely and clearly in the repair order for the information of the workshop personnel. Two examples for specifying the operation numbers:
Example 1
Vehicles with engine running complaint if no maintenance service is due.
in this case, perform operation "Testing, adjusting engine." Depending on the complaint, specify also combined operations, operation "Testing engine output and exhaust emissions on roller dynamometer."
Example 2
Vehicles with engine running complaint where maintenance service is due.
In order to avoid any overlapping, do not specify operation "Testing, adjusting engine" is already contained in part II of the maintenance service.
in this case, it is good practice to have part II conducted in the test group in order to perform any additional work which may be required as a combined operation.
instructions regarding work units book or standard texts and flat rates microfilm
The marking before the operation text in the work units documentation means that a detailed inclusive text is listed following the respective operation group.
The flat rates stated are matched to the operation procedures in the relevant microfilm Combustion I and II.
Notes for the workshop supervisor
The engine test program is structured in such a way that the repair order can be enlarged as required.
Enlargements as a result of additionally necessary combined operations must be justified by the results of tests and measurements.