Proposed Testing Procedure for Pre-Transmission Hybrid PowerPack Certification

11 May 2011

Conventional On-Highway Engine Test Certification Procedure

1. Torque Curve Generation

a. The engine is warmed to operating temperature (typically at mid-speed, mid-load point)

b. The engine returned to idle condition

c. The throttle ramped to 100%

d. While throttle is held at 100%, engine speed is ramped at 8rpm/s until a speed at which 

100% throttle results in 0 net torque

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

i. Throttle is set to 0% (the motoring rack position) and the speed is ramped at 

8rpm/s from the maximum speed back down to idle

ii. No further torque is measured, and the motoring torque curve is taken as being 

-40% of the positive torque curve

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, the normalized test 

cycle is denormalized 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. The engine system is run 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, the engine keyswitch is turned off and the 

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

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

c. At this point, the engine system is started and run, without warm up, over the FTP cycle

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

the keyswitch is off
e. At the end of this soak period, the engine system is restarted 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, 

the steady state cycle is generated. 

b. High and low test speeds, nhi and nlo, respectively, are calculated from the engine torque 

curve. 

c. Intermediate speeds A, B and C are calculated based upon nhi and nlo. 

d. 100%, 75%, 50% and 25% load points at each one of these intermediate speeds make up 

the test points, 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. The powerpack is warmed to operating temperature (typically at mid-speed, mid-load 

point)

b. The powerpack returned to idle condition

c. The throttle ramped to 100%

d. Throttle is held at 100% until engine torque stabilizes

e. At this point, with throttle held at 100%, engine speed is ramped at 8rpm/s until a speed 

at which 100% throttle results in 0 net torque

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. A predetermined number of speed points are picked at random

b. The powerpack is warmed to operating temperature (typically at mid-speed, mid-load 

point)

c. The powerpack is returned to idle speed at a throttle where power into energy storage = 

0

d. At each selected speed point, the throttle is set to produce 70% of the steady-state 

torque curve load at that speed. 

e. At this speed point, the throttle is ramped to 100% and held until the powerpack torque 

reaches a maximum value. Once the torque stabilizes, the throttle is returned to a 

setting to produce 70% of the steady-state torque curve value and held for 30 seconds.

f. The powerpack is returned to idle speed at a throttle where power into energy storage = 

0, and is then brought to the next speed point.

g. Steps (d) – (f) is repeated for the remaining selected speed points.

h. While throttle is held at 100%, engine speed is ramped at 8rpm/s until a speed at which 

100% throttle results in 0 net torque

i. The maximum torque at these speed points must fall within +/-5% of the nominal, 

manufacturer provided torque curve. If a certain number of points fall outside of this 

boundary, the test is stopped.

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 2 and defined calculations, the normalized test 

cycle is denormalized 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, and the torque is defined as follows:

1. The value of the -40% positive torque curve is taken as the motoring 

torque at the prescribed speed.

2. 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. The powerpack system is run 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, the engine keyswitch is turned off and the 

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

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

c. At this point, the engine system is started and run, without warm up, over the FTP cycle

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

the keyswitch is off

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

5. Steady State Cycle Generation

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

test schedule, the steady state cycle is generated. 

b. High and low test speeds, nhi and nlo, respectively, are calculated from the steady state 

engine torque curve. 

c. Intermediate speeds A, B and C are calculated based upon nhi and nlo. 

d. 100%, 75%, 50% and 25% load points at each one of these intermediate speeds make up 

the test points, 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) after each test cycle is run.

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

(in hp-hr)

a. 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. Energy storage management criteria met per J2711

c. 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.