40 CFR § 205.153 - Engine displacement.

---
identifier: "/us/cfr/t40/s205.153"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 205.153 - Engine displacement."
title_number: 40
title_name: "Protection of Environment"
section_number: "205.153"
section_name: "Engine displacement."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "G"
subchapter_name: "NOISE ABATEMENT PROGRAMS"
part_number: "205"
part_name: "TRANSPORTATION EQUIPMENT NOISE EMISSION CONTROLS"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "Secs. 6, 10, 11, 13, Pub. L. 92-574, 86 Stat. 1234 (42 U.S.C. 4905, 4909, 4910, 4912)."
regulatory_source: "41 FR 15544, Apr. 13, 1976, unless otherwise noted."
cfr_part: "205"
---


# 205.153 Engine displacement.

(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.

(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.

cc = (Maximum chamber volume−minimum chamber volume) × 3 × number of rotors.