Rich burn four stroke engine

{
  "id": "MLC-T-ENV-024303",
  "term": "Rich burn four stroke engine",
  "field": "Environment",
  "term_source": "Rich Burn Four Stroke Engine",
  "definition": "Four-stroke spark ignited reciprocating internal combustion engine where the manufacturer's recommended operating air/fuel ratio divided by the stoichiometric air/fuel ratio at full load conditions is less than or equal to 1.1. Internal combustion engines originally manufactured as rich burn engines but modified with passive emissions control technology for nitrogen oxides (NOX) (such as pre-combustion chambers) will be considered lean burn engines. Existing affected unit where there are no manufacturer's recommendations regarding air/fuel ratio will be considered rich burn engines if the excess oxygen content of the exhaust at full load conditions is less than or equal to 2 percent.",
  "subject": "Built environments",
  "references": [
    "40 CFR 52.41 (2023)"
  ],
  "url": "https://mlchart.com/terminology/environment/rich-burn-four-stroke-engine/"
}