Proposed Testing Procedure for Pre-Transmission Hybrid PowerPack Certification

14 May 2011

Conventional On-Highway Engine Test Certification Procedure

1. Torque Curve Generation

a. Warm engine to operating temperature (typically at a 75% power point)

b. Return engine to idle condition or at least 15 seconds.

c. Snap throttle to 100%

d. With throttle held at 100%, ramp engine speed from idle to the point above the max 

power point where 50% power is achieved.

i. The speed should be ramped at the appropriate rate such that the duration of 

the sweep is 4 to 6 minutes.

e. At this point, there are alternatives to creating a negative/motoring torque curve

i. Repeat steps (b) through (d), but with throttle set to 0% (minimum operator 

demand).

ii. Multiple the positive torque curve generated by -40%.

iii. Motor the engine at warm idle and at max speed, recording the motoring 

torque required. Interpolate between points to determine motoring torque.

2. Transient Cycle Generation

a. A normalized engine speed and load cycle is defined (the FTP cycle)

b. Using the torque curve defined in step 1 and defined calculations, denormalize the 

normalized test cycle into engine speed and torque commands

i. The speed is defined in the normalized cycle as a percentage of the range 

between idle speed (0% speed) and a maximum test speed (100% speed)

ii. The maximum test speed is defined as the speed at which the 100% load at that 

speed maximizes the length of the vector between that point and the idle point.

iii. The torque is defined in the normalized cycle as a percentage of the maximum 

torque at the corresponding test speed

c. Some points in the normalized cycle are defined as motoring points. At these points, 

the speed is defined as above, whereas the torque is defined as the value of the 

negative/motoring torque curve at the corresponding speed

3. Running Transient Test Cycle

a. Run the engine system over one or more conditioning FTP cycles, each separated by a 

20 minute hot soak period, during which the keyswitch is turned off

b. After the final conditioning cycle is run, turn off the engine keyswitch off and allow the 

engine to soak until the engine temperature has stabilized at ambient temperature 

(usually taken as oil temperature being less than 85degF)
c. At this point, start the engine system and run it, without warm up, over the FTP cycle

d. At the end of this “cold” cycle, soak the engine system for 20 minutes, during which the 

keyswitch is off

e. At the end of this soak period, restart the engine system and run over the FTP cycle

4. Steady State Cycle Generation

a. Using the engine torque curve defined in step 1, defined calculations and test schedule, 

generate the steady state cycle

b. Calculate high and low test speeds, nhi and nlo, respectively, from the engine torque 

curve. 

c. Calculate intermediate speeds A, B and C based upon nhi and nlo. 

d. The test points are defined by the 100%, 75%, 50% and 25% load points at each one of 

these intermediate speeds, and the engine transitions between these test points 

according to the test schedule

5. Running Steady State Test Cycle

a. The engine is warmed to operating condition

b. The steady state test cycle is run twice back-to-back

c. The first cycle is used as a conditioning cycle, and the second as the certification cycle

6. Data collection and analysis

a. Gaseous emissions data is collected and the total mass of the emissions is logged (in 

grams)

b. The positive work of the engine is summed over the length of the cycle and logged (in 

hp-hr)

c. The brake specific emissions are determined by dividing the mass of the collected 

emissions by the total positive cycle work.

7. Criteria for Successful Test Completion

a. Speed, Torque and Power regressions must meet minimum targets after point omission 

rules are applied

b. Determining emissions results

i. The brake specific gaseous emissions for the conditioning cycles are ignored

ii. The brake specific gaseous emissions for the transient cycle immediately 

following the cold soak period are multiplied by a weight factor of 1/7

iii. The brake specific gaseous emissions for the hot transient cycle (the next cycle 

run after the cold cycle) are multiplied by a weight factor of 6/7

iv. The weighted brake specific gaseous emissions of the two cycles are then 

summed to get a composite emissions value. This value must be less than the 

regulated limit.

v. The brake specific gaseous emissions for the steady state cycle must also be less 

than the regulated limit.
Proposed Hybrid Pre-Transmission PowerPack On-Highway Engine Test Certification Procedure

1. Steady State Torque Curve Generation

A positive torque curve is generated using only engine power to represent typical 

steady-state system performance.

a. Warm powerpack to operating temperature (typically at a 75% power point).

b. Return powerpack to idle condition or at least 15 seconds.

c. Snap throttle to 100%.

d. Hold throttle at 100% until engine torque stabilizes (and power from the energy storage 

is near 0kW).

e. With throttle held at 100%, ramp powerpack speed from idle to the point above the 

max power point where 50% power is achieved.

i. The speed should be ramped at the appropriate rate such that the duration of 

the sweep is 4 to 6 minutes.

f. Monitor energy storage power during sweep to ensure the torque curve produced is 

from engine only.

2. Transient Torque Curve Generation

A transient system torque curve, provided by the hybrid system manufacturer and 

covering the speed range from idle to maximum no load speed, is verified before the 

test. This torque curve is generated using both engine and battery power to represent 

typical transient system performance.

a. Warm powerpack to operating temperature (typically at a 75% power point)

b. Return powerpack to idle condition or at least 15 seconds.

c. Set throttle to a position that achieves 50-70% of the steady state torque curve value at 

this speed, and remain at this point for a time to be determined using good engineering 

judgment.

d. Snap throttle to 100%

e. With throttle held at 100%, ramp powerpack speed from the current speed to the next 

incrememental speed.

i. The speed should be ramped at a rate similar to that used to generate the 

steady state torque curve.

ii. The next incremental speed should be determined using good engineering 

judgment, ensuring that the energy storage system is capable of meeting full 

power requirements through to that speed.

f. Remaining at this speed, set throttle to a position that achieves 50-70% of the steady 

state torque curve value at this speed, and remain at this point for a time to be 

determined using good engineering judgment.

g. Repeat steps (d) through (f) until a speed point above the max power point where 50% 

power is achieved.

3. Transient Cycle Generation
a. A normalized engine speed and load cycle is defined (the FTP cycle)

b. Using the torque curve defined in step 1 and defined calculations, denormalize the 

normalized test cycle into engine speed and torque commands

i. The speed is defined in the normalized cycle as a percentage of the range 

between idle speed (0% speed) and a maximum test speed (100% speed)

ii. The maximum test speed is defined as the speed at which the 100% load at that 

speed maximizes the length of the vector between that point and the idle point.

iii. The torque is defined in the normalized cycle as a percentage of the maximum 

torque at the corresponding test speed

iv. Some points in the normalized cycle are defined as motoring points. At these 

points, the speed is defined as above, whereas the torque is defined defined as 

follows:

1. An appropriate Vehicle FTP cycle is calculated based upon peak 

powerpack power. A braking torque from this Vehicle FTP cycle is 

provided as a normalized braking torque schedule. This normalize 

braking torque schedule is denormalized by multiplying the schedule by 

the peak system torque (plus a constant).

These negative torque values are effectively a limit on regenerative braking 

torque. The regenerative braking energy captured by the powerpack during 

these motoring periods depends upon the state of the powerpack system, but is 

limited by the negative torque.

4. Running Transient Test Cycle

a. Run the powerpack over one or more conditioning FTP cycles, each separated by a 20 

minute hot soak period, during which the keyswitch is turned off

b. After the final conditioning cycle is run, turn off the powerpack keyswitch off and allow 

the powerpack to soak until the engine temperature has stabilized at ambient 

temperature (usually taken as oil temperature being less than 85degF)

c. At this point, start the powerpack and run it, without warm up, over the FTP cycle

d. At the end of this “cold” cycle, soak the powerpack for 20 minutes, during which the 

keyswitch is off

e. At the end of this soak period, restart the powerpack and run over the FTP cycle

5. Steady State Cycle Generation

a. Using the steady state powerpack torque curve defined in step 1, defined calculations 

and test schedule, generate the steady state cycle

b. Calculate high and low test speeds, nhi and nlo, respectively, from the steady state 

powerpack torque curve. 

c. Calculate intermediate speeds A, B and C based upon nhi and nlo. 

d. The test points are defined by the 100%, 75%, 50% and 25% load points at each one of 

these intermediate speeds, and the powerpack transitions between these test points 

according to the test schedule
6. Running Steady State Test Cycle

a. The powerpack is warmed to operating condition

b. The steady state test cycle is run twice back-to-back

c. The first cycle is used as a conditioning cycle, and the second as the certification cycle

7. Data collection and analysis

a. Gaseous emissions data is collected and the total mass of the emissions is logged (in 

grams)

b. The positive work of the powerpack is summed over the length of the cycle and logged 

(in hp-hr)

i. Any difference in stored energy levels between the start and finish of the test 

cycle should be addressed according to standards laid out in SAE J2711. 

c. The brake specific emissions are determined by dividing the mass of the collected 

emissions by the total positive cycle work.

8. Criteria for Successful Test Completion

a. Speed, Torque and Power regressions must meet minimum targets after point omission 

rules are applied

b. Determining emissions results

i. The brake specific gaseous emissions for the conditioning cycles are ignored

ii. The brake specific gaseous emissions for the transient cycle immediately 

following the cold soak period are multiplied by a weight factor of 1/7

iii. The brake specific gaseous emissions for the hot transient cycle (the next cycle 

run after the cold cycle) are multiplied by a weight factor of 6/7

iv. The weighted brake specific gaseous emissions of the two cycles are then 

summed to get a composite emissions value. This value must be less than the 

regulated limit.

v. The brake specific gaseous emissions for the steady state cycle must also be less 

than the regulated limit.

c. Energy storage management criteria met per J2711