[Code of Federal Regulations]
[Title 40, Volume 17]
[Revised as of July 1, 2004]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR86.420-78]

[Page 631-632]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 86_CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND 
ENGINES--Table of Contents
 
   Subpart E_Emission Regulations for 1978 and Later New Motorcycles, 
                           General Provisions
 
Sec. 86.420-78  Engine families.

    (a) The vehicles covered in the application will be divided into 
groupings whose engines are expected to have similar emission 
characteristics throughout their useful life. Each group of engines with 
similar emission characteristics shall be defined as a separate engine 
family.
    (b) Reciprocating families. To be classed in the same engine family, 
reciprocating engines must be identical in all of the following 
applicable respects:
    (1) The combustion cycle.
    (2) The cooling mechanism.
    (3) The cylinder configuration (inline, vee, opposed, bore spacings, 
etc.).
    (4) The number of cylinders.
    (5) The engine displacement class, Sec. 86.419.
    (6) The method of air aspiration.
    (7) The number of catalytic converters, location, volume, and 
composition.
    (8) The thermal reactor characteristics.
    (9) The number of carburetors.
    (10) The prechamber characteristics.
    (c) At the manufacturer's option, reciprocating engines identical in 
all the respects listed in paragraph (b) of this section may be further 
divided into different engine families if the Administrator determines 
that they may be expected to have different emission characteristics. 
This determination will be

[[Page 632]]

based upon a consideration of features such as:
    (1) The bore and stroke.
    (2) The combustion chamber configuration.
    (3) The intake and exhaust timing method of actuation (poppet valve, 
reed valve, rotary valve, etc.).
    (4) The intake and exhaust valve or port sizes, as applicable.
    (5) The fuel system.
    (6) The exhaust system.
    (d) Rotary families. To be classed in the same engine family, rotary 
combustion cycle engines must be identical in all of the following 
applicable respects:
    (1) The major axis of the epitrochoidal curve.
    (2) The minor axis of the epitrochoidal curve.
    (3) The generating radius of the epitrochoidal curve.
    (4) The cooling mechanism.
    (5) The number of rotors.
    (6) The engine displacement class, Sec. 86.419.
    (7) The method of air aspiration.
    (8) The number of catalytic converters, location, volume and 
composition.
    (9) The thermal reactor characteristics.
    (10) The number of carburetors.
    (11) The prechamber characteristics.
    (e) At the manufacturer's option, rotary combustion cycle engines 
identical in all the respects listed in paragraph (d) of this section, 
may be further divided into different engine families if the 
Administrator determines that they may be expected to have different 
emission characteristics. This determination will be based upon a 
consideration of features, such as:
    (1) The width of the rotor housing.
    (2) The type and location of intake port (side, peripheral, 
combination, etc.).
    (3) The number of spark plugs per rotor.
    (4) The fuel system.
    (5) The exhaust system.
    (f) Where engines are of a type which cannot be divided into engine 
families based upon the criteria listed in paragraphs (b) and (d) of 
this section, the Administrator will establish families of those engines 
based upon the features most related to their emission characteristics.

[42 FR 1126, Jan. 5, 1977, as amended at 44 FR 48205, Aug. 17, 1979]