Open main menu
Home
Random
Recent changes
Special pages
Community portal
Preferences
About Wikipedia
Disclaimers
Incubator escapee wiki
Search
User menu
Talk
Dark mode
Contributions
Create account
Log in
Editing
Dynamometer
(section)
Warning:
You are not logged in. Your IP address will be publicly visible if you make any edits. If you
log in
or
create an account
, your edits will be attributed to your username, along with other benefits.
Anti-spam check. Do
not
fill this in!
==Types of dynamometer test procedures== There are essentially 3 types of dynamometer test procedures: # Steady state: where the engine is held at a specified RPM (or series of usually sequential RPMs) for a desired amount of time by the variable brake loading as provided by the PAU (power absorber unit). These are performed with brake dynamometers. # Sweep test: the engine is tested under a load (i.e. inertia or brake loading), but allowed to "sweep" up in RPM, in a continuous fashion, from a specified lower "starting" RPM to a specified "end" RPM. These tests can be done with inertia or brake dynamometers. # Transient test: usually done with AC or DC dynamometers, the engine power and speed are varied throughout the test cycle. Different test cycles are used in different jurisdictions. Chassis test cycles include the US light-duty UDDS, HWFET, US06, SC03, ECE, EUDC, and CD34, while engine test cycles include ETC, HDDTC, HDGTC, WHTC, WHSC, and ED12. ===Types of sweep tests=== #'''Inertia sweep''': an inertia dyno system provides a fixed inertial mass flywheel and computes the power required to accelerate the flywheel (the load) from the starting to the ending RPM. The actual rotational mass of the engine (or engine and vehicle in the case of a chassis dyno) is not known, and the variability of even the mass of the tires will skew the power results. The inertia value of the flywheel is "fixed", so low-power engines are under load for a much longer time and internal engine temperatures are usually too high by the end of the test, skewing optimal "dyno" tuning settings away from the optimal tuning settings of the outside world. Conversely, high powered engines commonly complete a "4th gear sweep" test in less than 10 seconds, which is not a reliable load condition{{citation needed|date=January 2015}} as compared to operation in the real world. By not providing enough time under load, internal combustion chamber temperatures are unrealistically low and power readings - especially past the power peak - are skewed to the low side. #'''Loaded sweep''', of the brake dyno type, includes: ## '''Simple fixed load sweep''': a fixed load - of somewhat less than the output of the engine - is applied during the test. The engine is allowed to accelerate from its starting RPM to its ending RPM, varying at its own acceleration rate, depending on power output at any particular rotational speed. Power is calculated using (rotational speed x torque x constant) + the power required to accelerate the dyno and engine's/vehicle's rotating mass. ## '''Controlled acceleration sweep''': similar in basic usage as the (above) simple fixed load sweep test, but with the addition of active load control that targets a specific rate of acceleration. Commonly, 20fps/ps is used. #'''Controlled acceleration rate''': the acceleration rate used is controlled from low power to high power engines, and overextension and contraction of "test duration" is avoided, providing more repeatable tests and tuning results. In every type of sweep test, there remains the issue of potential power reading error due to the variable engine/dyno/vehicle total rotating mass. Many modern computer-controlled brake dyno systems are capable of deriving that "inertial mass" value, so as to eliminate this error.{{Original research inline|date=June 2011}} A "sweep test" will almost always be suspect, as many "sweep" users ignore the rotating mass factor, preferring to use a blanket "factor" on every test on every engine or vehicle. Simple inertia dyno systems aren't capable of deriving "inertial mass", and thus are forced to use the same (assumed) inertial mass on every vehicle tested. Using steady state testing eliminates the rotating inertial mass error of a sweep test, as there is no acceleration during this type of test. ===Transient test characteristics=== Aggressive throttle movements, engine speed changes, and engine motoring are characteristics of most transient engine tests. The usual purpose of these tests are vehicle emissions development and homologation. In some cases, the lower-cost eddy-current dynamometer is used to test one of the transient test cycles for early development and calibration. An eddy current dyno system offers fast load response, which allows rapid tracking of speed and load, but does not allow motoring. Since most required transient tests contain a significant amount of motoring operation, a transient test cycle with an eddy-current dyno will generate different emissions test results. Final adjustments are required to be done on a motoring-capable dyno. ===Engine dynamometer=== [[Image:TitanTestStand Rev2011.jpg|thumb|right|HORIBA engine dynamometer TITAN]] An [[engine dynamometer]] measures power and torque directly from the engine's [[crankshaft]] (or [[flywheel]]), when the engine is removed from the vehicle. These dynos do not account for power losses in the drivetrain, such as the [[gearbox]], [[Transmission (mechanics)|transmission]], and [[differential (mechanics)|differential]]. ===Chassis dynamometer (rolling road)=== {{main|Chassis dynamometer}} [[Image:chassisdyno.jpg|thumb|right|[[Saab 96]] on chassis dynamometer]] A [[chassis]] dynamometer, sometimes referred to as a rolling road,<ref>{{cite web |title=Rolling Road Dyno |url=http://www.tuningtools.co.uk/rolling-road-dyno-sales.html |work=Tuning Tools |access-date=3 August 2012 |archive-url=https://web.archive.org/web/20161203174940/http://www.tuningtools.co.uk/rolling-road-dyno-sales.html |archive-date=3 December 2016 |url-status=dead}}</ref> measures power delivered to the surface of the "drive roller" by the drive [[wheel]]s. The vehicle is often strapped down on the roller or rollers, which the car then turns, and the output measured thereby. Modern roller-type chassis dyno systems use the "Salvisberg roller",<ref>{{cite web |url=http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/PTO/search-bool.html&r=10&f=G&l=50&co1=AND&d=PTXT&s1=salvisberg&OS=salvisberg&RS=salvisberg |title=United States Patent: D798762 - Watch strap link |website=uspto.gov |access-date=7 April 2018}}</ref> which improves traction and repeatability, as compared to the use of smooth or [[Knurling|knurled]] drive rollers. Chassis dynamometers can be fixed or portable, and can do much more than display RPM, power, and torque. With modern electronics and quick reacting, low inertia dyno systems, it is now possible to tune to best power and the smoothest runs in real time. Other types of chassis dynamometers are available that eliminate the potential for wheel slippage on old style drive rollers, attaching directly to the vehicle's [[Wheel hub assembly|hubs]] for direct torque measurement from the axle. [[Motor vehicle emissions]] development and homologation dynamometer test systems often integrate emissions sampling, measurement, engine speed and load control, data acquisition, and safety monitoring into a complete test cell system. These test systems usually include complex emissions sampling equipment (such as constant volume samplers and raw [[exhaust gas]] sample preparation systems) and analyzers. These analyzers are much more sensitive and much faster than a typical portable exhaust gas analyzer. Response times of well under one second are common, and are required by many transient test cycles. In retail settings it is also common to tune the air-fuel ratio using a wideband [[oxygen sensor]] that is graphed along with the RPM. Integration of the dynamometer control system with automatic calibration tools for engine system calibration is often found in development test cell systems. In these systems, the dynamometer load and engine speed are varied to many engine operating points, while selected engine management parameters are varied and the results recorded automatically. Later analysis of this data may then be used to generate engine calibration data used by the engine management software. Because of frictional and mechanical losses in the various drivetrain components, the measured wheel brake horsepower is generally 15β20 percent less than the brake horsepower measured at the crankshaft or flywheel on an engine dynamometer.<ref>John Dinkel, "Chassis Dynamometer", ''Road and Track Illustrated Automotive Dictionary'', (Bentley Publishers, 2000) p. 46.</ref>
Edit summary
(Briefly describe your changes)
By publishing changes, you agree to the
Terms of Use
, and you irrevocably agree to release your contribution under the
CC BY-SA 4.0 License
and the
GFDL
. You agree that a hyperlink or URL is sufficient attribution under the Creative Commons license.
Cancel
Editing help
(opens in new window)