Feedgases: Predicting Functional and Non-Functioal Converters Using Grams/Mile Tailpipe Readings

These numbers assume good engine integrity and proper fuel control. All three gases must be considered during diagnostics.

Engine-Out Feedgases (pre-CAT) Tailpipe Gases (post-CAT)
(HC) F.I. Grams/Mile (HC) F.I. Grams/Mile
4 cyl 1.0-2.0 4 cyl 0.5-1.0
6 cyl 2.0-2.5 6 cyl 1.0-1.3
8 cyl 2.5-3.0 8 cyl 1.2-1.6
Carb Grams/Mile Carb Grams/Mile
4 cyl 1.5-2.5 4 cyl 0.8-1.2
6 cyl 2.5-3.5 6 cyl 1.2-1.5
8 cyl 3.0-5.0 8 cyl 1.5-2.5
(CO) F.I. Grams/Mile (CO) F.I. Grams/Mile
4 cyl 10.0-15.0 4 cyl 4.0-8.0
6 cyl 15.0-20.0 6 cyl 8.0-12.0
8 cyl 20.0-25.0 8 cyl 10.0-12.0
Carb Carb
4 cyl 15.0-25.0 4 cyl 6.0-12.0
6 cyl 25.0-30.0 6 cyl 12.0-15.0
8 cyl 30.0-45.0 8 cyl 15.0-20.0
(NOX) F.I. (NOX) F.I.
4 cyl 1.3-2.0 4 cyl 1.0-1.5
6 cyl 2.0-2.3 6 cyl 1.5-1.8
8 cyl 2.3-4.0 8 cyl 1.8-2.2
Carb Carb
4 cyl 1.5-2.5 4 cyl 1.2-1.6
6 cyl 2.0-2.5 6 cyl 1.6-2.0
8 cyl 2.5-4.5 8 cyl 2.0-2.5

Copyright ©1996 Colorado State University

Rev. August 16, 1996

HMC