# Title 40

## SECTION 1065.512

### 1065.512 Duty cycle generation.

§ 1065.512 Duty cycle generation.(a) Generate duty cycles according to this section if the standard-setting part requires engine mapping to generate a duty cycle for your engine configuration. The standard-setting part generally defines applicable duty cycles in a normalized format. A normalized duty cycle consists of a sequence of paired values for speed and torque or for speed and power.

(b) Transform normalized values of speed, torque, and power using the following conventions:

(1) *Engine speed for variable-speed engines.* For
variable-speed engines, normalized speed may be expressed as a
percentage between warm idle speed, *f*nidle, and maximum test
speed, *f*ntest, or speed may be expressed by referring to a
defined speed by name, such as “warm idle,” “intermediate speed,”
or “A,” “B,” or “C” speed. Section 1065.610 describes how to
transform these normalized values into a sequence of reference
speeds, *f*nref. Running duty cycles with negative or small
normalized speed values near warm idle speed may cause low-speed
idle governors to activate and the engine torque to exceed the
reference torque even though the operator demand is at a minimum.
In such cases, we recommend controlling the dynamometer so it gives
priority to follow the reference torque instead of the reference
speed and let the engine govern the speed. Note that the
cycle-validation criteria in § 1065.514 allow an engine to govern
itself. This allowance permits you to test engines with
enhanced-idle devices and to simulate the effects of transmissions
such as automatic transmissions. For example, an enhanced-idle
device might be an idle speed value that is normally commanded only
under cold-start conditions to quickly warm up the engine and
aftertreatment devices. In this case, negative and very low
normalized speeds will generate reference speeds below this higher
enhanced idle speed and we recommend controlling the dynamometer so
it gives priority to follow the reference torque, controlling the
operator demand so it gives priority to follow reference speed and
let the engine govern the speed when the operator demand is at
minimum.

(2) *Engine torque for variable-speed engines.* For
variable-speed engines, normalized torque is expressed as a
percentage of the mapped torque at the corresponding reference
speed. Section 1065.610 describes how to transform normalized
torques into a sequence of reference torques, *T*ref. Section
1065.610 also describes special requirements for modifying
transient duty cycles for variable-speed engines intended primarily
for propulsion of a vehicle with an automatic transmission. Section
1065.610 also describes under what conditions you may command
*T*ref greater than the reference torque you calculated from a
normalized duty cycle. This provision permits you to command
*T*ref values that are limited by a declared minimum torque.
For any negative torque commands, command minimum operator demand
and use the dynamometer to control engine speed to the reference
speed, but if reference speed is so low that the idle governor
activates, we recommend using the dynamometer to control torque to
zero, CITT, or a declared minimum torque as appropriate. Note that
you may omit power and torque points during motoring from the
cycle-validation criteria in § 1065.514. Also, use the maximum
mapped torque at the minimum mapped speed as the maximum torque for
any reference speed at or below the minimum mapped speed.

(3) *Engine torque for constant-speed engines.* For
constant-speed engines, normalized torque is expressed as a
percentage of maximum test torque, *T*test. Section 1065.610
describes how to transform normalized torques into a sequence of
reference torques, *T*ref. Section 1065.610 also describes
under what conditions you may command *T*ref greater than the
reference torque you calculated from the normalized duty cycle.
This provision permits you to command *T*ref values that are
limited by a declared minimum torque.

(4) *Engine power.* For all engines, normalized power is
expressed as a percentage of mapped power at maximum test speed,
*f*ntest, unless otherwise specified by the standard-setting
part. Section 1065.610 describes how to transform these normalized
values into a sequence of reference powers, *P*ref. Convert
these reference powers to corresponding torques for operator demand
and dynamometer control. Use the reference speed associated with
each reference power point for this conversion. As with cycles
specified with % torque, issue torque commands more frequently and
linearly interpolate between these reference torque values
generated from cycles with % power.

(5) *Ramped-modal cycles.* For ramped-modal cycles,
generate reference speed and torque values at 1 Hz and use this
sequence of points to run the cycle and validate it in the same
manner as with a transient cycle. During the transition between
modes, linearly ramp the denormalized reference speed and torque
values between modes to generate reference points at 1 Hz. Do not
linearly ramp the normalized reference torque values between modes
and then denormalize them. Do not linearly ramp normalized or
denormalized reference power points. These cases will produce
nonlinear torque ramps in the denormalized reference torques. If
the speed and torque ramp runs through a point above the engine's
torque curve, continue to command the reference torques and allow
the operator demand to go to maximum. Note that you may omit power
and either torque or speed points from the cycle-validation
criteria under these conditions as specified in § 1065.514.

(c) For variable-speed engines, command reference speeds and
torques sequentially to perform a duty cycle. Issue speed and
torque commands at a frequency of at least 5 Hz for transient
cycles and at least 1 Hz for steady-state cycles (*i.e.*,
discrete-mode and ramped-modal). Linearly interpolate between the 1
Hz reference values specified in the standard-setting part to
determine more frequently issued reference speeds and torques.
During an emission test, record the feedback speeds and torques at
a frequency of at least 5 Hz for transient cycles and at least 1 Hz
for steady-state cycles. For transient cycles, you may record the
feedback speeds and torques at lower frequencies (as low as 1 Hz)
if you record the average value over the time interval between
recorded values. Calculate the average values based on feedback
values updated at a frequency of at least 5 Hz. Use these recorded
values to calculate cycle-validation statistics and total work.

(d) For constant-speed engines, operate the engine with the same
production governor you used to map the engine in § 1065.510 or
simulate the in-use operation of a governor the same way you
simulated it to map the engine in § 1065.510. Command reference
torque values sequentially to perform a duty cycle. Issue torque
commands at a frequency of at least 5 Hz for transient cycles and
at least 1 Hz for steady-state cycles (*i.e.*, discrete-mode,
ramped-modal). Linearly interpolate between the 1 Hz reference
values specified in the standard-setting part to determine more
frequently issued reference torque values. During an emission test,
record the feedback speeds and torques at a frequency of at least 5
Hz for transient cycles and at least 1 Hz for steady-state cycles.
For transient cycles, you may record the feedback speeds and
torques at lower frequencies (as low as 1 Hz) if you record the
average value over the time interval between recorded values.
Calculate the average values based on feedback values updated at a
frequency of at least 5 Hz. Use these recorded values to calculate
cycle-validation statistics and total work.

(e) You may perform practice duty cycles with the test engine to optimize operator demand and dynamometer controls to meet the cycle-validation criteria specified in § 1065.514.

[73 FR 37317, June 30, 2008, as amended at 79 FR 23774, Apr. 28, 2014]