Powertrain Performance Test (useful technical info)
Powertrain Performance Test
TEST INFORMATION:
All published tests have been conducted in a laboratory at RRI’s facility south of Stockholm Sweden. The R&D board of Rototest Research Institute is convinced that RRI’s test results is to become a world-wide standard for vehicle Powertrain Performance™ measurements and Performance Graphs. The Certificates of Performance are proudly produced with the highest quality level with the possibility to be verified by performance professionals around the world.
Scientific usage of ROTOTEST chassis dynamometers
The chassis dynamometer is the key element for producing Powertrain Performance™ measurements and respected Performance Graphs. Rototest Research Institute has scientific demands on all published measurements and the dynamometer has to produce correct and non-disputable results. For more information about the dynamometer equipment please visit www.rototest.com
The same test conditions
To produce comparable and repeatable measurements it is of importance that the test conditions are kept the same. Rototest Research Institute has a strict demand on test cell cooling capacity. The ROTOTEST dynamometers produce a strong airflow in accordance to the absorbed load. For “after-cooling” (no load and/or speed on the dynamometers) and for additional airflow, electrical fans are used. Dedicated electrical fans are used for intercoolers.
Powertrain Performance definition
Rototest Research Institute defines Powertrain Performance™ as the engine performance reduced by the losses through the drivetrain (transmission, differential, joints, etc). Simplified - Powertrain Performance is the performance available to the wheels.
Powertrain Performance Valuation definition
The Powertrain Performance Valuation™ (power rate, torque rate) is the exchange rate between the claimed engine performance and the actual performance available to the wheels.
TORQUE, SPEED AND POWER
The dynamometer measures drive wheel torque [Nm, lb-ft, kgm] and drive wheel speed [1/min (rpm)] (and/or engine speed [1/min (rpm)] where applicable). The physical relationship between Torque, Speed and Power is that torque times speed results in power. The equation using SI units is:
P = M x w
where
P is power, expressed in W
M is torque, expressed in Nm
w is angular velocity, expressed in rad/s
Approximate equations
To allow easier calculation there are a number of approximate equations available of which a few are presented below. The equations will introduce a small error as they are using a limited number of decimals and should not be used other than when approximate values are enough.
kW / Nm
Power [kW] = Torque [Nm] x Speed [1/min] / 9549
Torque [Nm] = 9549 x Power [kW] / Speed [1/min]
PS (metric hp) / Nm
Power [PS] = Torque [Nm] x Speed [1/min] / 7019
Torque [Nm] = 7019 x Power [PS] / Speed [1/min]
bhp (imperial hp) / lb-ft
Power [bhp] = Torque [lb-ft] x Speed [1/min] / 5252
Torque [lb-ft] = 5252 x Power [bhp] / Speed [1/min]
Conversions
1 kW ≈ 1.34 bhp (imperial hp)
1 kW ≈ 1.36 PS (metric hp)
1 bhp (imperial hp) ≈ 1.015 PS (metric hp)
1 lb-ft ≈ 1.36 Nm
1 Nm ≈ 0.735 lb-ft
NOTE!
Performance Graphs (torque and power) always have the relations above. Graphs that do not (regardless of whether they are called Performance Curves, Power Graphs, Power curves, Power and Torque Curves, Dyno Runs, Dyno Graphs or Dyno Curves) fulfil these relations are based on bad measurements and/or bad “after adjustments” and may indicate intentional disinformation.
WHY POWERTRAIN PERFORMANCE MEASUREMENTS
To address why Powertrain Performance should be measured, Rototest Research Institute has published a White Paper where Powertrain Performance measurements versus engine performance is discussed. The paper also includes statistical data where stated engine performance is compared to powertrain performance. [more...]
Test results - Rototest Certificate of Performance
Page one: Performance Graphs with drive wheel torque and wheel power. Stated engine performance is in some cases presented for comparison.
Page two: Background information. Power and torque corrections for spark ignition naturally aspirated gasoline engines are made according to ISO 1585 standards. Non-corrected measurements values are always present; an important quality feature to allow others to judge the significance of the presented corrections.
NOTE!
Modern computer controlled engines have the possibility to self-correct for ambient conditions (increase, decrease power). This is especially true for forced induction (turbo, compressor, etc) equipped engines where the boost can be controlled to absolute levels (instead of relative). Applying a correction on engines with a self-correction feature is incorrect and is not allowed according to the standard.
ISO 1585 correction formula
fc = ( 990 / p )^1.2 x (( T + 273 ) / 298 )^0.6
where
fc is the correction factor applied to power and torque
p is the dry absolute atmospheric pressure, expressed in mbar
T is the inlet air temperature, expressed in °C
Note!
8 mbar higher atmospheric pressure ≈ 1% more power
5°C lower inlet temperature ≈ 1% more power
Background information
Background information parameters include:
Atmospheric pressure [mbar]
Ambient temperature [°C]
Air relative humidity [%]
Engine inlet temperature [°C]
Engine oil temperature [°C]
Engine speed [rpm]
Measurement time [s]
Torque presentation
Torque is presented as total drive wheel torque divided by the total transmission reduction (i.e. the gear ratio times the final reduction ratio)
Additional test information
- All tests are performed with a warmed up test vehicle drive train.
- All unnecessary electrical consumers are switched off.
- AC and power steering is not in use.
- Brakes are controlled for dragging (the wheels are removed).
- All tests are performed with the engine hood open.
Stated engine performance
Where applicable is the Engine Performance plotted together with the Powertrain Performance in the Performance Graph as a comparison. The source of the stated engine performance is always declared. The source is commonly the auto manufacturer, a respected motor magazine, an engine tuner or the supplier of performance part(s).
Ref. http://www.rri.se/ - Rototest Research Institute
P.S.
this explains for example why BMW rate the E46 or Z4M at 343PS while magazines quote it as 338bhp.. it's not Euro vs US thing, it's PS vs bhp :read:
TEST INFORMATION:
All published tests have been conducted in a laboratory at RRI’s facility south of Stockholm Sweden. The R&D board of Rototest Research Institute is convinced that RRI’s test results is to become a world-wide standard for vehicle Powertrain Performance™ measurements and Performance Graphs. The Certificates of Performance are proudly produced with the highest quality level with the possibility to be verified by performance professionals around the world.
Scientific usage of ROTOTEST chassis dynamometers
The chassis dynamometer is the key element for producing Powertrain Performance™ measurements and respected Performance Graphs. Rototest Research Institute has scientific demands on all published measurements and the dynamometer has to produce correct and non-disputable results. For more information about the dynamometer equipment please visit www.rototest.com
The same test conditions
To produce comparable and repeatable measurements it is of importance that the test conditions are kept the same. Rototest Research Institute has a strict demand on test cell cooling capacity. The ROTOTEST dynamometers produce a strong airflow in accordance to the absorbed load. For “after-cooling” (no load and/or speed on the dynamometers) and for additional airflow, electrical fans are used. Dedicated electrical fans are used for intercoolers.
Powertrain Performance definition
Rototest Research Institute defines Powertrain Performance™ as the engine performance reduced by the losses through the drivetrain (transmission, differential, joints, etc). Simplified - Powertrain Performance is the performance available to the wheels.
Powertrain Performance Valuation definition
The Powertrain Performance Valuation™ (power rate, torque rate) is the exchange rate between the claimed engine performance and the actual performance available to the wheels.
TORQUE, SPEED AND POWER
The dynamometer measures drive wheel torque [Nm, lb-ft, kgm] and drive wheel speed [1/min (rpm)] (and/or engine speed [1/min (rpm)] where applicable). The physical relationship between Torque, Speed and Power is that torque times speed results in power. The equation using SI units is:
P = M x w
where
P is power, expressed in W
M is torque, expressed in Nm
w is angular velocity, expressed in rad/s
Approximate equations
To allow easier calculation there are a number of approximate equations available of which a few are presented below. The equations will introduce a small error as they are using a limited number of decimals and should not be used other than when approximate values are enough.
kW / Nm
Power [kW] = Torque [Nm] x Speed [1/min] / 9549
Torque [Nm] = 9549 x Power [kW] / Speed [1/min]
PS (metric hp) / Nm
Power [PS] = Torque [Nm] x Speed [1/min] / 7019
Torque [Nm] = 7019 x Power [PS] / Speed [1/min]
bhp (imperial hp) / lb-ft
Power [bhp] = Torque [lb-ft] x Speed [1/min] / 5252
Torque [lb-ft] = 5252 x Power [bhp] / Speed [1/min]
Conversions
1 kW ≈ 1.34 bhp (imperial hp)
1 kW ≈ 1.36 PS (metric hp)
1 bhp (imperial hp) ≈ 1.015 PS (metric hp)
1 lb-ft ≈ 1.36 Nm
1 Nm ≈ 0.735 lb-ft
NOTE!
Performance Graphs (torque and power) always have the relations above. Graphs that do not (regardless of whether they are called Performance Curves, Power Graphs, Power curves, Power and Torque Curves, Dyno Runs, Dyno Graphs or Dyno Curves) fulfil these relations are based on bad measurements and/or bad “after adjustments” and may indicate intentional disinformation.
WHY POWERTRAIN PERFORMANCE MEASUREMENTS
To address why Powertrain Performance should be measured, Rototest Research Institute has published a White Paper where Powertrain Performance measurements versus engine performance is discussed. The paper also includes statistical data where stated engine performance is compared to powertrain performance. [more...]
Test results - Rototest Certificate of Performance
Page one: Performance Graphs with drive wheel torque and wheel power. Stated engine performance is in some cases presented for comparison.
Page two: Background information. Power and torque corrections for spark ignition naturally aspirated gasoline engines are made according to ISO 1585 standards. Non-corrected measurements values are always present; an important quality feature to allow others to judge the significance of the presented corrections.
NOTE!
Modern computer controlled engines have the possibility to self-correct for ambient conditions (increase, decrease power). This is especially true for forced induction (turbo, compressor, etc) equipped engines where the boost can be controlled to absolute levels (instead of relative). Applying a correction on engines with a self-correction feature is incorrect and is not allowed according to the standard.
ISO 1585 correction formula
fc = ( 990 / p )^1.2 x (( T + 273 ) / 298 )^0.6
where
fc is the correction factor applied to power and torque
p is the dry absolute atmospheric pressure, expressed in mbar
T is the inlet air temperature, expressed in °C
Note!
8 mbar higher atmospheric pressure ≈ 1% more power
5°C lower inlet temperature ≈ 1% more power
Background information
Background information parameters include:
Atmospheric pressure [mbar]
Ambient temperature [°C]
Air relative humidity [%]
Engine inlet temperature [°C]
Engine oil temperature [°C]
Engine speed [rpm]
Measurement time [s]
Torque presentation
Torque is presented as total drive wheel torque divided by the total transmission reduction (i.e. the gear ratio times the final reduction ratio)
Additional test information
- All tests are performed with a warmed up test vehicle drive train.
- All unnecessary electrical consumers are switched off.
- AC and power steering is not in use.
- Brakes are controlled for dragging (the wheels are removed).
- All tests are performed with the engine hood open.
Stated engine performance
Where applicable is the Engine Performance plotted together with the Powertrain Performance in the Performance Graph as a comparison. The source of the stated engine performance is always declared. The source is commonly the auto manufacturer, a respected motor magazine, an engine tuner or the supplier of performance part(s).
Ref. http://www.rri.se/ - Rototest Research Institute
P.S.
this explains for example why BMW rate the E46 or Z4M at 343PS while magazines quote it as 338bhp.. it's not Euro vs US thing, it's PS vs bhp :read:
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