§610.21 Device functional category and vehicle system effects.

(a) The devices evaluated in this program are organized into categories for purposes of definition and establishment of evaluation criteria and test procedures, and to indicate which vehicle functional characteristics (other than fuel economy) may be adversely affected by installation or use of the device.

(b) A device's category will be based on:

(1) Engineering principles governing operation of the device;

(2) Interaction between the device and specific vehicle/engine operating characteristics; and

(3) Constraints with respect to vehicle applicability of the device.

(c) The device categories and the vehicle functional characteristics which may be adversely affected are noted for each device category in Table I. The notation for each characteristic is as follows: Exhaust emissions 1 Driveability 2 Durability 3 Performance 4

                                 Table 1
------------------------------------------------------------------------
                                             Characteristics adversely
            Device categories                         affected
------------------------------------------------------------------------
             Fuel-Air System
 
1  1  Carburetors and fuel injection       All.
 systems.
Air-fuel ratio modifiers (e.g., air        All.
 bleeds).
Atomization devices (acoustic and          All.
 mechanical).
Vapor Injectors..........................  All.
Choke controls...........................  1, 2, and 4.
Air filters..............................  1, 2, and 4.
Fuel-air distribution systems (intake      1, 2, and 4.
 manifolds).
Fuel pressure regulators.................  All.
 
             Ignition System
 
Spark plugs..............................  All.
Spark timing control systems.............  All.
Spark duration control systems...........  1, 4.
Spark energy sources.....................  1, 4.
 
         Emission Control Systems
 
Exhaust gas recirculation (EGR) systems..  All.
After-treatment devices..................  1, 2, and 4.
 
                Drivetrain
 
Tires....................................  1.
Overdrive units..........................  All.
Torque converter lockups.................  1, 2, and 4.
 
              Exhaust System
 
Headers..................................  1.
Tuned exhaust systems....................  1.
 
               Accessories
 
Cooling fan or cooling fan couplings.....  1.
Cold start aids (e.g., engine heaters)...  1.
 
               Lubrication
 
Oil filters..............................  3.
 
               Vehicle Body
 
Aerodynamic drag reduction devices.......  1.
 
              Miscellaneous
 
Modification to valve timing.............  All.
Retrofit prechambers.....................  All.
Fuel additives...........................  All.
Other miscellaneous......................  Potentially all.
------------------------------------------------------------------------

(d) In the absence of sufficient information from the device manufacturer on this topic or if the Administrator's preliminary analysis indicates that testing is necessary to determine the nature or extent of possible adverse effects of device installation and use on vehicle operation and performance, the Administrator will require such tests to be conducted prior to the publication of a complete evaluation of the device.

[44 FR 17946, Mar. 23, 1979, as amended at 49 FR 18489, May 1, 1984]