September 21, 2000
U.S. Environmental Protection Agency
Office of Transportation and Air Quality
Maximum Test Speed
(This note describes the process by which real operating data may
be converted to percentage of peak operation values in creating
test cycles and its reverse of converting test cycle values to
"target" torque and speed numbers for real operation.)
Data Normalization
This spreadsheet will create a normalized duty cycle from an
engine's raw or de- normalized speed and torque values with that
engine's torque validation/MAP (maximum achievable power) curve
and its low, or "curb", idle speed as inputs to the process.
Convert or "round-off" all values to whole numbers before pasting
them into the spreadsheet. Make sure that any previous MAP data
get deleted and that any previous speed and torque values get
deleted as well. From the input engine speed and torque values,
determine the highest speed value attained by the engine. Compare
this value to the highest speed reported in the engine's MAP
curve and note which is the higher speed. Next, extrapolate a
speed value in rpm for a "zero" torque point which is no more
than 3% higher than the higher input speed or MAP value. Paste
the MAP curve into the spreadsheet, making the "zero" point the
final value in the MAP curve. There should be only one point in
the MAP curve with a "zero" torque value. Next, paste the speed
and torque data into the appropriate columns (in red) in the
spreadsheet. Be sure to enter the low idle speed. If you do not
know the engine's low idle speed, the program will use the lowest
speed on the MAP curve. Calculate the spreadsheet at this time.
The resulting normalized speed and torque values constitute a
duty cycle over which another engine might be operated for
comparison. Charts are available within the spreadsheet to
quickly check to see that the engine operating data and
normalized cycle both make sense.
Cycle Denormalization
This spreadsheet will change a normalized duty cycle into a
set of denormalized or "target" speed and torque operating values
with an engine's torque validation/MAP curve and its low idle
speed as inputs to the process. Enter a "target lug curve" for
the engine you would like to test with a new normalized cycle.
Paste the normalized cycle into the appropriate columns (in red)
in the spreadsheet. Convert or "round-off" all values to whole
numbers before pasting them into the spreadsheet. Make sure that
any previous MAP data and percent of speed and torque values get
deleted. From the percent of engine speed and torque input
values, determine the highest percent of speed value to be
attained by the engine. Compare this value to the highest speed
reported in the engine's MAP curve and note which is the higher
speed. Next, extrapolate a speed value in rpm for a "zero"
torque point which is no more than 3% higher than the higher of
the input speed or MAP value. Paste the "target" MAP curve into
the spreadsheet, making the "zero" torque point the final value
in the MAP curve. There should be only one point in the engine's
MAP curve with a "zero" torque value. Next, paste the percent
speed and torque values from the input cycle into the appropriate
columns (in red) in the spreadsheet. Be sure to enter the
engine's low idle speed. If you do not know the engine's low
idle speed, the program will use the lowest speed from the MAP
curve. Calculate the spreadsheet at this time. The resulting de-
normalized cycle will be the actual speed and torque values over
which a particular engine would be operated to run the duty
cycle. Again, charts are available within the spreadsheet to
quickly check to see that the input duty cycle and the resulting
speed and torque value set both make sense.
Final MAP/Lug Curve Speed Input
The transient sweep Maximum Achievable Power (MAP) curve,
typically recorded at a rate of 8 rpm per second, or the steady
state step MAP should have a final speed, beyond measured rated
speed (speed at maximum measured power), that has a torque value
of 30% of the full load torque at idle speed. For selection of
the maximum test speed for the maximum speed normalization of the
duty cycle, it should be 3% beyond the final speed of the MAP
curve.
(Data processing tip: from within Excel software, go to
Tools, Options, Calculate and switch on "manual calculate."
Press F9 to calculate new values within the spreadsheets.
This speeds processing of spreadsheets if you were previously
calculating new cycles each time you changed a number. Each
spreadsheet is processor and RAM-intensive, about 3MB per
file, so expect delays in computing)