§ 85.2122 Emission-critical parameters.

(a) The following parts may be certified in accordance with § 85.2114(b):

(1) Carburetor Vacuum Break (Choke Pull-Off). (i) The emission-critical parameters for carburetor vacuum breaks are:

(A) Diaphragm Displacement.

(B) Timed Delay.

(C) Modulated Stem Displacement.

(D) Modulated Stem Displacement Force.

(E) Vacuum Leakage.

(ii) For the purposes of this paragraph:

(A) “Diaphragm Displacement” means the distance through which the center of the diaphragm moves when activated. In the case of a non-modulated stem, diaphragm displacement corresponds to stem displacement.

(B) “Timed Delay” means a delayed diaphragm displacement controlled to occur within a given time period.

(C) “Modulated Stem Displacement” means the distance through which the modulated stem may move when actuated independent of diaphragm displacement.

(D) “Modulated Stem Displacement Force” means the amount of force required at start and finish of a modulated stem displacement.

(E) “Vacuum Leakage” means leakage into the vacuum cavity of a vacuum break.

(F) “Vacuum Break” (“Choke Pull-off”) means a vacuum-operated device to open the carburetor choke plate a predetermined amount on cold start.

(G) “Modulated Stem” means a stem attached to the vacuum break diaphragm in such a manner as to allow stem displacement independent of diaphragm displacement.

(H) “Vacuum Purge System” means a vacuum system with a controlled air flow to purge the vacuum system of undesirable manifold vapors.

(2) Carburetor Choke Thermostats. (i) The emission-critical parameters for all Choke Thermostats are:

(A) Thermal Deflection Rate.

(B) Mechanical Torque Rate.

(C) Index Mark Position.

(ii) The emission-critical parameters for Electrically-Heated Choke Thermostats are:

(A) Those parameters set forth in paragraph (a)(2)(i) of this section

(B) Time to rotate coil tang when electrically energized

(C) Electrical circuit resistance

(D) Electrical switching temperature

(iii) For the purpose of this paragraph:

(A) “Choke” means a device to restrict air flow into a carburetor in order to enrich the air/fuel mixture delivered to the engine by the carburetor during cold-engine start and cold-engine operation.

(B) “Thermostat” means a temperature-actuated device.

(C) “Electrically-heated Choke” means a device which contains a means for applying heat to the thermostatic coil by electrical current.

(D) “Thermostatic Coil” means a spiral-wound coil of thermally-sensitive material which provides rotary force (torque) and/or displacement as a function of applied temperature.