[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2003]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR90.116]

[Page 185-186]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 90--CONTROL OF EMISSIONS FROM NONROAD SPARK-IGNITION ENGINES AT OR 
BELOW 19 KILOWATTS--Table of Contents
 
       Subpart B--Emission Standards and Certification Provisions
 
Sec. 90.116  Certification procedure--determining engine displacement, 
engine class, and engine families.

    (a) Engine displacement must be calculated using nominal engine 
values and rounded to the nearest whole cubic centimeter in accordance 
with ASTM E29-93a. This procedure has been incorporated by reference. 
See Sec. 90.7.
    (1) Class I-A--nonhandheld equipment engines less than 66 cc in 
displacement;
    (2) Class I-B--nonhandheld equipment engines greater than or equal 
to 66 cc but less than 100 cc in displacement;
    (3) Class I--nonhandheld equipment engines greater than or equal to 
100 cc but less than 225 cc in displacement;
    (4) Class II--nonhandheld equipment engines greater than or equal to 
225 cc in displacement;
    (5) Class III--handheld equipment engines less than 20 cc in 
displacement,

[[Page 186]]

    (6) Class IV--handheld equipment engines equal or greater than 20 cc 
but less than 50 cc in displacement, and
    (7) Class V--handheld equipment engines equal to or greater than 50 
cc in displacement.
    (c) The manufacturer's product line will be divided into groupings 
of engine families as specified by paragraph (d) of this section.
    (d) To be classed in the same engine family, 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, 
and so forth);
    (4) The number of cylinders;
    (5) The engine class;
    (6) The location of valves, where applicable, with respect to the 
cylinder (e.g. side valves or overhead valves);
    (7) The number of catalytic converters, location, volume and 
composition;
    (8) The thermal reactor characteristics;
    (9) The fuel required (e.g. gasoline, natural gas, LPG); and
    (10) The useful life category.
    (e) At the manufacturer's option, 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 is based upon the 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, and so forth);
    (4) The intake and exhaust valve or port sizes, as applicable;
    (5) The fuel system;
    (6) The exhaust system; and
    (7) The method of air aspiration.
    (f) Where engines are of a type which cannot be divided into engine 
families based upon the criteria listed in paragraph (d) of this 
section, the Administrator will establish families for those engines 
based upon the features most related to their emission characteristics.

[60 FR 34598, July 3, 1995, as amended at 64 FR 15239, Mar. 30, 1999; 65 
FR 24308, Apr. 25, 2000]