CPC Vehicle Systems

Question 1

What is the function of the turbocharger in a modern HGV diesel engine?

Accepted Answer

To force more air into the engine cylinders, increasing power output and efficiency

Answer

A turbocharger uses exhaust gas energy to spin a turbine that compresses intake air, forcing more air (and therefore more fuel) into the combustion chambers. This increases power output without increasing engine size, also improving fuel efficiency.

Question 2

What is the purpose of the EGR (Exhaust Gas Recirculation) system?

Accepted Answer

To reduce nitrogen oxide (NOx) emissions by recirculating a portion of exhaust gas back into the engine

Answer

The EGR system reduces NOx emissions by recirculating a controlled amount of exhaust gas back into the intake manifold. This lowers combustion temperatures, which reduces the formation of nitrogen oxides, a major pollutant.

Question 3

What type of braking system do most modern HGVs use?

Accepted Answer

Air-operated (pneumatic) disc or drum brakes

Answer

Most modern HGVs use air-operated (pneumatic) braking systems with disc or drum brakes. Compressed air operates the brake chambers, which push the brake pads against the disc or drums against the shoes. Air brakes are preferred because they are fail-safe.

Question 4

What is the function of the air compressor in an HGV?

Accepted Answer

To generate compressed air for the braking system, suspension, and other pneumatic systems

Answer

The engine-driven air compressor generates compressed air that is stored in air tanks and used to operate the brakes, air suspension, and other pneumatic systems. Maintaining correct air pressure is critical for brake safety.

Question 5

What does the ABS (Anti-lock Braking System) do on an HGV?

Accepted Answer

It prevents the wheels from locking during heavy braking, allowing the driver to maintain steering control

Answer

ABS prevents wheel lock-up during heavy braking by rapidly modulating brake pressure to individual wheels. This maintains tyre grip and allows the driver to continue steering the vehicle while braking, reducing the risk of jackknifing and skidding.

DVSA UK Driving Theory Practice Test

DVSA UK Driving Theory Practice Test

CPC Vehicle Systems