View all text of Subpart E [§ 7.81 - § 7.92]
§ 7.87 - Test to determine the maximum fuel-air ratio.
(a) Test procedure. (1) Couple the diesel engine to the dynamometer and connect the sampling and measurement devices specified in § 7.86.
(2) Prior to testing, zero and span the CO and NO
(3) While running the engine, the following shall apply:
(i) The parameter for the laboratory atmospheric factor, f
(A) The equation is f
(B) The equation is f
(ii) The air inlet restriction shall be set within ±10 percent of the recommended maximum air inlet restriction as specified by the engine manufacturer at the engine operating condition giving maximum air flow to determine the concentration of CO as specified in paragraph (a)(6) of this section.
(iii) The exhaust backpressure restriction shall be set within ±10 percent of the maximum exhaust backpressure as specified by the engine manufacturer at the engine operating condition giving maximum rated horsepower to determine the concentrations of CO and NO
(iv) The air inlet restriction shall be set within ±10 percent of a recommended clean air filter at the engine operating condition giving maximum air flow as specified by the engine manufacturer to determine the concentration of NO
(4) The engine shall be at a steady-state condition when the exhaust gas samples are collected and other test data is measured.
(5) In a category A engine, 1.0 ±0.1 percent CH
(6) Operate the engine at several speed/torque conditions to determine the concentrations of CO and NO
(b) Acceptable performance. The CO and NO