Title 40

SECTION 1036.525

1036.525 Hybrid engines.

§ 1036.525 Hybrid engines.

(a) If your engine system includes features that recover and store energy during engine motoring operation, test the engine as described in paragraph (d) of this section. For purposes of this section, features that recover energy between the engine and transmission are considered related to engine motoring.

(b) If you produce a hybrid engine designed with power take-off capability and sell the engine coupled with a transmission, you may calculate a reduction in CO2 emissions resulting from the power take-off operation as described in 40 CFR 1037.540. Quantify the CO2 reduction for your engines using the vehicle-based procedures, consistent with good engineering judgment.

(c) For engines that include electric hybrid systems, test the engine with the hybrid electric motor, the rechargeable energy storage system (RESS), and the power electronics between the hybrid electric motor and the RESS. You may ask us to modify the provisions of this section for testing engines with other kinds of hybrid systems.

(d) Measure emissions using the same procedures that apply for testing non-hybrid engines under this part, except as specified in this part and 40 CFR part 1065. For ramped-modal testing, deactivate the hybrid features unless we specify otherwise. The following provisions apply for testing hybrid engines:

(1) Engine mapping. Map the engine as specified in 40 CFR 1065.510. This requires separate torque maps for the engine with and without the hybrid features active. For transient testing, denormalize the duty cycle using the map generated with the hybrid feature active. For steady-state testing, denormalize the duty cycle using the map generated without the hybrid feature.

(2) Engine shutdown during testing. If you will configure production engines to shut down automatically during idle operation, you may let the engine shut down during the idle portions of the duty cycle.

(3) Work calculation. Calculate positive and negative work done over the cycle according to 40 CFR 1065.650(d), except that you must set power to zero to calculate negative work done for any period over the cycle where the engine produces net positive power or where the negative power is solely from the engine and not the hybrid system.

(4) Limits on braking energy. Calculate brake energy fraction, xb, as follows:

(i) Calculate xb as the integrated negative work over the cycle divided by the integrated positive work over the cycle according to Eq. 1036.525-1. Calculate the brake energy limit for the engine, xbl, according to Eq. 1036.525-2. If xb is less than or equal to xbl, use the integrated positive work for your emission calculations. If xb is greater than xbl use Eq. 1036.525-3 to calculate an adjusted value for cycle work, Wcycle, and use Wcycle as the work value for calculating emission results. You may set an instantaneous brake target that will prevent xb from being larger than xbl to avoid the need to subtract extra brake work from positive work.

Where: Wneg = the negative work over the cycle. Wpos = the positive work over the cycle. Where: Pmax = the maximum power of the engine with the hybrid system engaged. Where: Wcycle = cycle work when xb is greater than xbl. Example: Wneg = 4.69 kW-hr Wpos = 14.67 kW-hr Pmax = 223 kW xbl = 4.158.10−4·.223 + 0.2247 = 0.317 kW since xb > xbl; Wcycle = 14.67 − (|4.59| − 0.317·14.67) = 14.63 kW-hr

(ii) Convert from g/kW-hr to g/hp-hr as the final step in calculating emission results.

(5) State of charge. Correct for the net energy change of the energy storage device as described in 40 CFR 1066.501.