Summary of EPA heavy-duty engine standards for MY 2027+

Key Takeaways

 

New standards apply to heavy-duty (HD) engines starting model year 2027

Required NOx reduction of 82.5% on existing FTP & RMC lab transient test cycles

New low load cycle adopted from California with tighter-than-CARB limits for full useful life

New methodology adopted for analyzing off-cycle emissions. Emissions will be analyzed using moving average window method and separated into 2 bins (vs. 3 in California). One bin for idle and low load emissions, another for high load emissions.

Full useful life extended from current 435,000 miles to 650,000 miles. Durability demonstration required out to 750,000 miles to account for real-world deterioration.

New SET cycle required for spark ignition engines. Same limits and useful life for compression ignition and spark ignition engines.

Warranty periods increased from 100,000 miles today to 450,000 miles for heavy HD engines. This increases the period under warranty from 23% to 70% of useful life.

Powertrain test cycles developed for hybrids and full powertrain testing of hybrids allowed for compliance

No NOx or PM emission credits for zero-emitting vehicles (ZEVs)

Standards will drive adoption of increased SCR volume and new technologies (e.g. close-coupled SCR with dual dosing, cylinder deactivation, heated urea dosing, electrically heated catalysts)

Summary of standards

Compression-ignition HD engine standards

Units: mg/hp-hr

NOx

HC

PM

CO

Current

MY2027+

Current

MY2027+

Current

MY2027

Current

MY2027+

SET & FTP*

200

35

140

60

10

5

15,500

6,000

LLC**

–

50

–

140

–

5

–

6,000

          *FTP 1/7 cold and 6/7 hot weighting factors kept unchanged

            **LLC requires applying accessory loads of 1.5, 2.5 and 3.5 kW for light, medium and heavy HDE

 

Spark-Ignition HD Engine Standards

Units: mg/hp-hr

NOx

HC

PM

CO

Current

MY2027+

Current

MY2027+

Current

MY2027

Current

MY2027+

SET (new)*

–

35

–

60

–

5

–

14,400

FTP

200

35

140

60

10

5

14,200

6,000

          *New SET duty cycle to address high load operation

Off-cycle limits for 2-Bin MAW* approach

 

NOx

HC

PM

CO

Bin 1**: Idle, low load (g/hr)

10

–

–

–

Bin 2**: Higher power (mg/hp-hr)

58

120

7.5

9,000

                                 *MAWs of 300 sec interval, continuous engine operation. No prescribed routes.

                                **Bin 1: Normalized average CO2 ≤ 6%    Bin 2: Normalized average CO2 > 6%

 

Useful Life for compression-ignition (and spark-ignition) HD engines

 

Current

MY2027+

Miles / Years

Hours

Miles / Years

Hours

 

Light HDE

110,000 / 10

–

270,000 / 15

13,000

 

Medium HDE

185,000 / 10

–

350,000 / 12

17,000

 

Heavy HDE

435,000 / 10

22,000

650,000 / 11

32,000

 

       

 

Emission-related warranty periods for HD engines

 

Current

MY2027+

Miles / Years

Hours

Miles / Years

Hours

 

Spark-ignition HDE

50,000 / 5

–

160,000 / 10

8,000

 

Light HDE

50,000 / 5

–

210,000 / 10

10,000

 

Medium HDE

100,000 / 5

–

280,000 / 10

14,000

 

Heavy HDE

100,000 / 5

–

450,000 / 10

22,000

 

       

Notes

  • NOx compliance allowance of 15 mg/hp-hr for in-use testing for duty cycles and for off-cycle Bin 2.
  • Include infrequent regenerations. EPA estimates IRAF to be 2 mg/hp-hr for FTP/SET and 5 mg/hp-hr for LLC.
  • Deterioration factor (DF) based on durability test to demonstrate compliance over useful life.
  • Discharge of crankcase emissions into ambient air must be accounted for. Estimated to be ~ 6 mg/hp-hr.
  • For Heavy HDE, durability demonstration required out to 750,000 miles

Comparison with California’s Ultra-Low NOx Omnibus Rule for Heavy HD Engines

For Heavy HD engines

  • Unlike EPA, California has an intermediate life standard at 435,000 miles, for which standards are more stringent than at full useful life (FUL)
  • FTP / RMC
    • California limits are tighter (20 mg/hp-hr) than EPA up to 435,000 miles. At FUL, the limits are the same at 35 mg/hp-hr. FUL is higher for EPA, at 650,000 miles than California at 600,000 miles.

 

  • Beyond 2031, California further extends FUL to 800,000 miles, but also relaxes the limits at FUL to 40 mg/hp-hr on FTP/RMC and 100 mg/hp-hr on LLC (so the EPA limits are in effect tighter over 435,000 to 650,000 miles).
  • Low load cycle (LLC)
    • The EPA limit of 50 mg/hp-hr is tighter than California’s 90 mg/hp-hr at FUL. California’s limit is the same as EPA only up to the intermediate life of 435,000 miles.
  • Note that unlike CARB, the EPA provides a NOx compliance allowance of 15 mg/hp-hr for in-use testing to account for test procedure variability, fuel quality and field aging effects.
  • Manufacturers can voluntarily certify to an idle NOX standard of 30 g/hr for MY 2024 to MY 2026, and 10 g/hr for MY 2027 and beyond using a CARB’s idle test procedure. CO, HC and PM do not need to be measured.

 

Electrified Powertrains

Hybrids

  • Powertrain test cycles developed which allow manufacturers to test the hybrid engine and powertrain together to demonstrate compliance with standards starting MY 2023.
  • Standards must be met under the worst-case conditions by testing under both charge-depleting and charge-sustaining operation.

ZEVs

  • No NOx or PM emission credits
  • Durability requirements not finalized, will be part of future regulations

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