{"data":{"id":"us/40-cfr-205.153","jurisdiction":"us","citation":"40 CFR 205.153","heading":"Engine displacement.","body":"(a) Engine displacement must be calculated using nominal engine values and rounded to the nearest whole cubic centimeter, in accordance with American Society for Testing Materials (ASTM) E 29-67.\n(b) For rotary engines, displacement means the maximum volume of a combustion chamber between two rotor tip seals minus the minimum volume of that combustion chamber between those two rotor seals times three times the number of rotors.\ncc = (Maximum chamber volume−minimum chamber volume) × 3 × number of rotors.","path":["Title 40—Protection of Environment","CHAPTER I—ENVIRONMENTAL PROTECTION AGENCY","SUBCHAPTER G—NOISE ABATEMENT PROGRAMS","PART 205—TRANSPORTATION EQUIPMENT NOISE EMISSION CONTROLS","Subpart D—Motorcycles"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-40.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:04Z","sha256":"8540d2bb68668a9666762bb6c2d632e0afcc3874f9f86741a1afe88ac040f779","source_id":"us-cfr","stale":true,"prev":"us/40-cfr-205.152","next":"us/40-cfr-205.154"},"notice":"GroundRules: Original legal text. Not legal advice."}