India: Heavy-Duty Truck and Bus Engines

Emission Standards
OBD Requirements

Emission Standards

Emission standards for new heavy-duty onroad engines—applicable to vehicles of GVW > 3,500 kg—are listed in Table 1. Limits for BS V shown in Table 1 were proposed in November 2015 [3297][3298] but later removed from an updated proposal [3349], transitioning the nation directly to BS VI from BS IV. BS VI requirements went into effect 2020.04 [5938].

**Table 1**
Emission standards for heavy-duty engines
Stage	Year	Test	CO	HC	CH₄	NOx	PM	PN	NH₃
Stage	Year	Test	g/kWh					kWh^-1	ppm
	1992	ECE R49	17.3	2.7		-	-
	1996	ECE R49	11.2	2.4		14.4	-
India 2000	2000	ECE R49	4.5	1.1		8.0	0.36^a
BS II	2005†	ECE R49	4.0	1.1		7.0	0.15
BS III	2010†	ESC	2.1	0.66		5.0	0.10
BS III	2010†	ETC	5.45	0.78		5.0	0.16
BS IV	2010‡	ESC	1.5	0.46		3.5	0.02
BS IV	2010‡	ETC	4.0	0.55		3.5	0.03
BS V	n/a ^b	ESC	1.5	0.46		2.0	0.02
BS V	n/a ^b	ETC	4.0	0.55	1.1^c	2.0	0.03
BS VI	2020	WHSC (CI)	1.5	0.13		0.40	0.01	8.0×10¹¹	10
		WHTC (CI)	4.0	0.16		0.46	0.01	6.0×10¹¹	10
		WHTC (PI)	4.0	0.16^d	0.50	0.46	0.01	6.0×10¹¹	10
† earlier introduction in selected regions, see India: Table 1 ‡ only in selected regions, see India: Table 1 ^a 0.612 for engines below 85 kW ^b Initially proposed in 2015.11 [3297][3298] but removed from a 2016.02 proposal [3349] ^c For CNG engines only ^d NMHC for PI engines

The BS VI standard also includes a limit for ammonia emissions, which should not exceed 10 ppm for compression ignition as well as positive ignition engines.

BS VI gasoline engines are certified with E5 or E10 and diesel engines with B7. Other regulated fuel types include CNG/Bio-methane/Biogas/LNG, LPG, E85, hydrogen, HCNG (hydrogen + CNG), ethanol-diesel blends (ED95), biodiesel blends up to B100 and dual fuel engines (diesel + CNG/LNG) [5939].

In-use compliance test procedures for BS VI engines are defined in an Automotive Industry Standard (AIS-137) published by the Automotive Research Association of India [5490]. A PEMS test at type approval and COP for vehicles with BS VI engines is required. From 2020.04, the PEMS test is for data collection only and from 2023.04, a conformity factor applies. The maximum in-use conformity factor for CO, THC, NMHC, CH₄ and NOx is 1.50 [5940][3349]. Off-cycle limits following the WNTE cycle must also be met by compression ignition and dual fuel engines.

OBD Requirements

BS VI OBD standards were implemented in two phases: Phase-I went into effect in April 2020 and Phase-II in April 2023 [5938]. OBD requirements are similar to those for Europe. Table 2 summarizes the phase-in schedule.

**Table 2**
OBD threshold limits (OTL)
Stage	Date	Vehicle Category	NOx	CO	PM
Stage	Date	Vehicle Category	g/kWh
BS V	n/a ^a	All	7.0		0.1^b
BS VI OBD-I	2020.04	CI engines	1.5		Performance monitoring
BS VI OBD-I	2020.04	Gas engines†	1.5		-
BS VI OBD-II	2023.04	CI engines	1.2		0.025
BS VI OBD-II	2023.04	Gas engines†	1.2	7.5	-
^a Initially proposed in 2015.11 [3297][3298] but removed from a 2016.02 proposal [3349] ^b CI engines only † All gas fueled engines and PI engines fitted to vehicles category M₃, to N₂ vehicles having a maximum permissible mass > 7.5 tonnes, and to N₃ vehicles

More details on Euro I-VI regulations and testing requirements can be found in the EU heavy-duty engine standards page.