Which gases are produced if the fuel mixture is not completely burnt?

• Carbon monoxide and hydrogen

• Oxides of nitrogen

• Carbon dioxide and water

• Methane and ethane

What is the purpose of adding additives to fuel?

• To increase the fuel's color

• To improve the anti-knock quality

• To decrease the fuel's density

• To reduce the fuel's cost

What is a common effect of engine modifications to meet emission regulations?

• Increase in fuel consumption

• Decrease in engine size

• Increase in engine noise

• Decrease in vehicle weight

What shape should the combustion chamber be to avoid unburnt fuel?

• Long and narrow

• Compact

• Wide and flat

• Cylindrical

What is the main factor controlling flame speed in an engine?

• Fuel type

• Chamber shape

• Engine size

• Exhaust type

What system is used to recycle some of the exhaust gas back into the induction manifold?

• Exhaust gas re-circulation (EGR)

• Turbocharging

• Supercharging

• Fuel injection

Why can't lead be used in vehicles with catalytic converters?

• It is too expensive

• It damages the converters

• It increases fuel consumption

• It reduces engine speed

What is a common solution to reduce NOx when the engine is under full load?

• Increase fuel injection

• Use of EGR system

• Decrease engine size

• Increase engine speed

What happens if the flame speed is too slow in an engine?

• All fuel is burnt

• Some of the charge remains unburnt

• NOx levels decrease

• Engine power increases

What is the effect of using a high compression ratio with a compact chamber?

• Low flame speed

• Excessively high temperature

• Reduced NOx production

• Increased fuel efficiency