EU: Nonroad SI Engines
The first EU emission standards for small spark ignited (SI) engines were adopted in 2002. These regulations were applicable to small SI engines below 19 kW. Under the Stage V regulations adopted in 2016, the standards are tightened and extended on more SI engine categories. The main rulemaking steps include:
Stage I/II. The regulations were introduced by Directive 2002/08/EC  that amended the nonroad emission Directive 97/68/EC by adding emission standards for small hand-held and non-hand-held SI engines below 19 kW. The regulation also extended the applicability of Stage II standards on constant speed engines. The standards became effective from August 2004 and fully phased-in by early 2009.
Stage V. The Stage V emission regulations  tighten exiting standards and introduce other important changes—For spark ignited engines, the scope is widened by introducing emission standards for SI engines above 19 kW and other previously unregulated categories of SI engines. Stage V standards cover the following categories of spark ignited engines:
- Category NRSh—Spark ignited engines below 19 kW exclusively for use in hand-held machinery;
- Category NRS—Spark ignited engines below 56 kW that are not included in category NRSh;
- Category SMB—Spark ignited engines used in snowmobiles;
- Category ATS—Spark ignited engines used in all terrain and side-by-side vehicles.
In addition, SI engines ≥ 56 kW are included in Category NRE and must meet the applicable emission standards for that category.
Stage I/II Standards
Stage I and Stage II emission limits are listed in Table 1 and in Table 2, respectively. The standards are applicable to small utility engines with a net power ≤ 19 kW (Class S). The effective dates are applicable to new type approvals—the respective market placement dates are six months later.
|SH:1||V < 20||2004.08.11||805||295||5.36|
|SH:2||20 ≤ D < 50||2004.08.11||805||241||5.36|
|SH:3||V ≥ 50||2004.08.11||603||161||5.36|
|SN:1||V < 66||2004.08.11||519||50|
|SN:2||66 ≤ V < 100||2004.08.11||519||40|
|SN:3||100 ≤ V < 225||2004.08.11||519||16.1|
|SN:4||V ≥ 225||2004.08.11||519||13.4|
|SH:1||V < 20||2007.08||805||50|
|SH:2||20 ≤ D < 50||2007.08||805||50|
|SH:3||V ≥ 50||2008.08||603||72|
|SN:1||V < 66||2004.08||610||50.0|
|SN:2||66 ≤ V < 100||2004.08||610||40.0|
|SN:3||100 ≤ V < 225||2007.08||610||16.1|
|SN:4||V ≥ 225||2006.08||610||12.1|
|* Additionally, NOx for all engine classes must not exceed 10 g/kWh|
Notwithstanding the definition of hand-held engine, two-stroke Stage I/II engines used to power snowthrowers only have to meet SH:1, SH:2 or SH:3 standards.
Emissions at Stage I/II are measured over one of four steady-state engine dynamometer test cycles (ISO 8178), depending on the type of machinery:
- Cycle D (D2 cycle of ISO 8178)—Engines with constant speed and intermittent load such as generating sets;
- Cycle G1—Non-hand-held intermediate speed applications;
- Cycle G2—Non-hand-held rated speed applications;
- Cycle G3—Hand-held applications.
Stage V Standards
Spark Ignited Utility Engines
Stage V emission standards for hand-held SI utility engines below 19 kW (category NRSh) are listed in Table 1, and those for non-hand-held SI engines below 56 kW (NRS) are shown in Table 2. Dates in the tables are market placement dates; new type approval dates are one year earlier.
Spark inited engines above 56 kW must meet emission standards for category NRE engines.
|NRSh-v-1a||V < 50||2019||805||50|
|NRSh-v-1b||V ≥ 50||2019||603||72|
|Category||Power (P)||Displacement (V)||Date||CO||HC+NOx|
|NRS-vr/vi-1a||P < 19||80 ≤ V < 225||2019||610||10|
|NRS-vr/vi-1b||V ≥ 225||2019||610||8|
|NRS-v-2a||19 ≤ P < 30||V ≤ 1000||2019||610||8|
|NRS-v-2b||V > 1000||2019||4.40*||2.70*|
|NRS-v-3||30 ≤ P < 56||any||2019|
|* Or any combination of values satisfying the equation (HC+NOx) × CO0.784 ≤ 8.57 and the conditions CO ≤ 20.6 g/kWh and (HC+NOx) ≤ 2.7 g/kWh|
Emission standards for spark ingited engines used in snowmobiles are listed in Table 5.
|SMB-v-1||P > 0||2019||275||75||-|
All Terrain Vehicle Engines
Emission standards for spark ingited engines used in all terrain and side-by-side vehicles are listed in Table 6.
|ATS-v-1||P > 0||2019||400||8|
Emissions from the above engine categories are tested over various non-road steady-state cycles, NRSC (generally based on the ISO 8178):
- Engines category NRSh (hand-held engines): Cycle G3;
- Engines category NRS:
- Power below 19 kW, intermediate speed applications (NRS-vi-1a/1b): Cycle G1;
- Power below 19 kW, rated speed applications (NRS-vr-1a/1b) Cycle G2;
- Power between 19 kW and 30 kW, displacement below 1 liter (NRS-v-2a): Cycle G2;
- Power above 19 kW, other (NRS-v-2b and NRS-v-3): Cycle C2;
- Snowmobile engines (SMB): Cycle H;
- All terrain engines (ATS): Cycle G1.