CEI CEI Fuel Systems & Engine Combustion

Question 1

Which combustion byproduct is formed when carbon-based fuels burn incompletely due to insufficient oxygen?

Accepted Answer

Carbon monoxide (CO)

Answer

Carbon monoxide (CO) is produced during incomplete combustion when there is insufficient oxygen to fully oxidize carbon to CO2.

Question 2

What is the stoichiometric air-to-fuel ratio for a gasoline-powered internal combustion engine?

Accepted Answer

14.7:1 (14.7 parts air to 1 part fuel by mass)

Answer

The stoichiometric air-to-fuel ratio for gasoline is 14.7:1, meaning 14.7 grams of air are required to completely combust 1 gram of gasoline with no excess oxygen or unburned fuel.

Question 3

How do oxides of nitrogen (NOx) primarily form during internal combustion engine operation?

Accepted Answer

At high combustion temperatures, atmospheric nitrogen reacts with oxygen inside the combustion chamber

Answer

NOx forms primarily through the thermal Zeldovich mechanism, where the high temperatures in the combustion chamber (above ~1,300°C) cause atmospheric nitrogen and oxygen to react.

Question 4

What does a rich air-fuel mixture (lambda < 1) typically produce in excess in vehicle exhaust compared to a stoichiometric mixture?

Accepted Answer

Higher CO and HC emissions due to incomplete combustion from excess fuel

Answer

A rich mixture (excess fuel) leads to incomplete combustion, producing elevated CO and unburned hydrocarbon (HC) emissions because there is insufficient oxygen to fully oxidize all the fuel.

Question 5

Which fuel system component is responsible for atomizing and injecting precise amounts of fuel into the engine's intake ports or combustion chamber?

Accepted Answer

Fuel injector

Answer

Fuel injectors are electronically controlled solenoid valves that atomize and deliver precise quantities of fuel into the intake port or directly into the combustion chamber based on ECU commands.

CEI - Certified Emission Inspector Practice Test

CEI - Certified Emission Inspector Practice Test

CEI CEI Fuel Systems & Engine Combustion