Heavy-Duty Diesel Truck and Bus Engines

• Regulatory Framework
• Emission Standards

Regulatory Framework

European emission regulations for new heavy-duty diesel engines are commonly referred to as Euro I ... VI. Sometimes Arabic numerals are also used (Euro 1 ... 6). We will use Roman numerals when referencing standards for heavy-duty engines, and reserve Arabic numerals for light-duty vehicle standards.

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The emission standards apply to all motor vehicles with a “technically permissible maximum laden mass” over 3,500 kg, equipped with compression ignition engines or positive ignition natural gas (NG) or LPG engines.

The regulations were originally introduced by the Directive 88/77/EEC, followed by a number of amendments. In 2005, the regulations were re-cast and consolidated by the Directive 05/55/EC. Beginning with the Euro VI stage, the legislation will be simplified, as “directives”—which need to be transposed into all of the national legislations—will be replaced by “regulations” which are directly applicable. The following are some of the most important rulemaking steps in the heavy-duty engine regulations:

• Euro I standards were introduced in 1992, followed by the introduction of Euro II regulations in 1996. These standards applied to both truck engines and urban buses, the urban bus standards, however, were voluntary.
• In 1999, the EU adopted Directive 1999/96/EC, which introduced Euro III standards (2000), as well as Euro IV/V standards (2005/2008). This rule also set voluntary, stricter emission limits for extra low emission vehicles, known as “enhanced environmentally friendly vehicles” or EEVs.
• In 2001, the European Commission adopted Directive 2001/27/EC which prohibits the use of emission “defeat devices” and “irrational” emission control strategies, which would be reducing the efficiency of emission control systems when vehicles operate under normal driving conditions to levels below those determined during the emission testing procedure.
• Directive 2005/55/EC adopted by the EU Parliament in 2005 introduced durability and OBD requirements, as well as re-stated the emission limits for Euro IV and Euro V which were originally published in 1999/96/EC. In a “split-level” regulatory approach, the technical requirements pertaining to durability and OBD—including provisions for emission systems that use consumable reagents—have been described by the Commission in Directive 2005/78/EC.
• In December 2007, the Commission published a proposal for Euro VI emission standards [COM(2007) 851]. The new emission limits, comparable in stringency to the US 2010 standards, would become effective from 2013/2014. The proposal represents the political part of the regulation. In the “split-level” approach, the technical details will be developed by the Commission at a later date.

Emission Standards

The following table contains a summary of the emission standards and their implementation dates. Dates in the tables refer to new type approvals; the dates for all type approvals are in most cases one year later (EU type approvals are valid longer than one year).

Table 1
EU Emission Standards for HD Diesel Engines, g/kWh (smoke in m^-1)

Tier	Date	Test	CO	HC	NOx	PM	Smoke
Euro I	1992, < 85 kW	ECE R-49	4.5	1.1	8.0	0.612
	1992, > 85 kW		4.5	1.1	8.0	0.36
Euro II	1996.10		4.0	1.1	7.0	0.25
	1998.10		4.0	1.1	7.0	0.15
Euro III	1999.10, EEVs only	ESC & ELR	1.5	0.25	2.0	0.02	0.15
	2000.10	ESC & ELR	2.1	0.66	5.0	0.10 0.13a	0.8
Euro IV	2005.10		1.5	0.46	3.5	0.02	0.5
Euro V	2008.10		1.5	0.46	2.0	0.02	0.5
Euro VI†	2013.04b		1.5	0.13	0.4	0.01
† Proposal (2007.12.21) a - for engines of less than 0.75 dm3 swept volume per cylinder and a rated power speed of more than 3000 min-1 b - 2014.10 for all models

Since the Euro III standard (2000), the earlier steady-state engine test ECE R-49 has been replaced by two cycles: the European Stationary Cycle (ESC) and the European Transient Cycle (ETC). Smoke opacity is measured on the European Load Response (ELR) test. The following testing requirements apply:

1. Compression ignition (diesel) engines:
   • Euro III:
     1. Conventional diesel engines: ESC/ELR test
     2. Diesel engines with “advanced aftertreatment” (NOx aftertreatment or DPFs) and EEVs: ESC/ELR + ETC
   • Euro IV and later: ESC/ELR + ETC
2. Positive ignition gas (natural gas, LPG) engines, Euro III and later: ETC cycle

Emission standards for diesel engines that are tested on the ETC test cycle, as well as for heavy-duty gas engines, are summarized in Table 2.

Table 2
Emission Standards for Diesel and Gas Engines, ETC Test, g/kWh

Tier	Date	Test	CO	NMHC	CH4a	NOx	PMb
Euro III	1999.10, EEVs only	ETC	3.0	0.40	0.65	2.0	0.02
	2000.10	ETC	5.45	0.78	1.6	5.0	0.16 0.21c
Euro IV	2005.10		4.0	0.55	1.1	3.5	0.03
Euro V	2008.10		4.0	0.55	1.1	2.0	0.03
Euro VI†	2013.04d		4.0	0.16e	0.5	0.4	0.01
† Proposal (2007.12.21) a - for gas engines only (Euro III-V: NG only; Euro VI: NG + LPG) b - not applicable for gas fueled engines at the Euro III-IV stages c - for engines with swept volume per cylinder < 0.75 dm3 and rated power speed > 3000 min-1 d - 2014.10 for all models e - THC for diesel engines

Euro VI Proposal. Additional provisions of the Euro VI proposal include:

• An ammonia (NH₃) concentration limit of 10 ppm applies to diesel (ESC + ETC) and gas (ETC) engines.
• A particle number limit is planned (pending the final results of the UN/ECE Particulate Measurement Programme, PMP), in addition to the mass limit. The number limit would prevent the possibility that the Euro VI PM mass limit is met using technologies (such as “open filters”) that would enable a high number of ultra fine particles to pass.
• The world-harmonized test cycles—WHSC and WHTC—will be used for Euro VI testing. WHSC/WHTC based limit values will be introduced once correlation factors with the current ESC/ETC tests are established.
• A maximum limit for the NO₂ component of NOx emissions may be defined at a later time.

Emission Durability. Effective October 2005 for new type approvals and October 2006 for all type approvals, manufacturers should demonstrate that engines comply with the emission limit values for useful life periods which depend on the vehicle category, as shown in the following table.

Table 3
Emission Durability Periods

Vehicle Category†	Period*
	Euro IV-V	Euro VI
N1 and M2	100 000 km / 5 years	160 000 km / 5 years
N2 N3 ≤ 16 ton M3 Class I, Class II, Class A, and Class B ≤ 7.5 ton	200 000 km / 6 years	300 000 km / 6 years
N3 > 16 ton M3 Class III, and Class B > 7.5 ton	500 000 km / 7 years	700 000 km / 7 years
† Mass designations (in metric tons) are “maximum technically permissible mass” * km or year period, whichever is the sooner

Effective October 2005 for new type approvals and October 2006 for all type approvals, type approvals also require confirmation of the correct operation of the emission control devices during the normal life of the vehicle under normal conditions of use (“conformity of in-service vehicles properly maintained and used”).

Early Introduction of Clean Engines. EU Member States are allowed to use tax incentives in order to speed up the marketing of vehicles meeting new standards ahead of the regulatory deadlines. Such incentives have to comply with the following conditions:

• they apply to all new vehicles offered for sale on the market of a Member State which comply in advance with the mandatory limit values set out by the Directive,
• they cease when the new limit values come into effect
• for each type of vehicle they do not exceed the additional cost of the technical solutions introduced to ensure compliance with the limit values.

Early introduction of cleaner engines can be also stimulated by such financial instruments as preferential road toll rates. In Germany, road toll discounts were introduced in 2005 which stimulated early launch of Euro V trucks.

Under the Euro VI proposal, incentives can also be given for scrapping existing vehicles or retrofitting them with emission controls.