---
kind: "section"
citation: "40 C.F.R. § 1037.555"
title: "40"
number: "1037.555"
heading: "Special procedures for testing Phase 1 hybrid systems."
url: "https://uscodex.org/cfr/40/1037.555"
---

# §1037.555. Special procedures for testing Phase 1 hybrid systems.


This section describes a powertrain testing procedure for simulating a chassis test with a pre-transmission or post-transmission hybrid system to perform A to B testing of Phase 1 vehicles. These procedures may also be used to perform A to B testing with non-hybrid systems. See [40 CFR 1036.545](/cfr/40/1036.545.md) for Phase 2 and later hybrid systems.

- (a) Set up the engine according to [40 CFR 1065.110](/cfr/40/1065.110.md) to account for work inputs and outputs and accessory work.
- (b) Collect CO2 emissions while operating the system over the test cycles specified in [§ 1037.510(a)(1)](/cfr/40/1037.510.md?p=a-1).
- (c) **Collect and measure emissions as described in 40 CFR part 1066.** Calculate emission rates in grams per ton-mile without rounding. Determine values for A, B, C, and M for the vehicle being simulated as specified in [40 CFR part 1066](/cfr/40/part1066.md). If you will apply an improvement factor or test results to multiple vehicle configurations, use values of A, B, C, M, ka, and r that represent the vehicle configuration with the smallest potential reduction in greenhouse gas emissions as a result of the hybrid capability.
- (d) Calculate the transmission output shaft's angular speed target for the driver model, fnref,driver, from the linear speed associated with the vehicle cycle using the following equation:
- (e) Use speed control with a loop rate of at least 100 Hz to program the dynamometer to follow the test cycle, as follows:
  - (1) Calculate the transmission output shaft's angular speed target for the dynamometer, fnref,dyno, from the measured linear speed at the dynamometer rolls using the following equation:
  - (2) For each test, validate the measured transmission output shaft's speed with the corresponding reference values according to [40 CFR 1065.514(e)](/cfr/40/1065.514.md?p=e). You may delete points when the vehicle is stopped. Perform the validation based on speed values at the transmission output shaft. For steady-state tests (55 mi/hr and 65 mi/hr cruise), apply cycle-validation criteria by treating the sampling periods from the two tests as a continuous sampling period. Perform this validation based on the following parameters:
- (f) Send a brake signal when operator demand is equal to zero and vehicle speed is greater than the reference vehicle speed from the test cycle. Set a delay before changing the brake state to prevent the brake signal from dithering, consistent with good engineering judgment.
- (g) The driver model should be designed to follow the cycle as closely as possible and must meet the requirements of [§ 1037.510](/cfr/40/1037.510.md) for steady-state testing and [40 CFR 1066.425](/cfr/40/1066.425.md) for transient testing. The driver model should be designed so that the brake and throttle are not applied at the same time.
- (h) Correct for the net energy change of the energy storage device as described in [40 CFR 1066.501(a)(3)](/cfr/40/1066.501.md?p=a-3).
- (i) Follow the provisions of [§ 1037.510](/cfr/40/1037.510.md) to weight the cycle results and [§ 1037.615](/cfr/40/1037.615.md) to calculate improvement factors and benefits for advanced technologies for Phase 1 vehicles.

## Notes

### Amendments

[81 FR 74048, Oct. 25, 2016, as amended at 86 FR 34483, June 29, 2021; 88 FR 4652, Jan. 24, 2023; 89 FR 29786, Apr. 22, 2024; 91 FR 7791, Feb. 18, 2026]

### Authority

Authority: 42 U.S.C. 7401—7671q.

### Source

Source: 81 FR 74048, Oct. 25, 2016, unless otherwise noted.

### Amendments

[81 FR 74048, Oct. 25, 2016, as amended at 86 FR 34483, June 29, 2021; 88 FR 4652, Jan. 24, 2023; 89 FR 29786, Apr. 22, 2024; 91 FR 7791, Feb. 18, 2026]