What happened to gasoline in the mid 1970s?
Hydrocarbons:
Fuels are made up of hydrocarbons and some small quantity inorganics.
When burned the Hydrogen and carbon are seperated and join with other components mostly oxygen, and turn into something else.
The something elses are generally CO, CO2, and various NOx combinations and some leftover (or possibly altered) HCs. Depending on the temperatures, mixing etc there is sometimes also H2O, and various Ox.
It is absolutely correct that higher HC is to be expected in the exhaust when the engine is at or near full load because it will be using relatively rich mixtures. It's also when there is the least amount of O2 leftover.
Back when I had pre-cat cars a chart like the one above was helpful in knowing which way to adjust idle mix if it didn't pass the idle sniff test.
From Motor Gasolines Technical Review
p. 31
PDF for download.
Hydrocarbons:
Fuels are made up of hydrocarbons and some small quantity inorganics.
When burned the Hydrogen and carbon are seperated and join with other components mostly oxygen, and turn into something else.
The something elses are generally CO, CO2, and various NOx combinations and some leftover (or possibly altered) HCs. Depending on the temperatures, mixing etc there is sometimes also H2O, and various Ox.
It is absolutely correct that higher HC is to be expected in the exhaust when the engine is at or near full load because it will be using relatively rich mixtures. It's also when there is the least amount of O2 leftover.
Back when I had pre-cat cars a chart like the one above was helpful in knowing which way to adjust idle mix if it didn't pass the idle sniff test.
From Motor Gasolines Technical Review
p. 31
PDF for download.
