Car Tuning Engine Performance Principles 3

Question 1

What is 'brake specific fuel consumption' (BSFC) used to measure?

Accepted Answer

The mass of fuel consumed per unit of power output per unit of time

Answer

BSFC measures engine efficiency by quantifying fuel mass consumed per horsepower-hour (or kW-hour), allowing comparison across different engine sizes.

Question 2

What happens to an engine's power output when intake air temperature increases?

Accepted Answer

Power decreases because hot air is less dense and contains less oxygen per volume

Answer

Hot air is less dense, meaning fewer oxygen molecules per cubic foot, which reduces the amount of fuel that can be burned and lowers power output.

Question 3

What does a 'stroker kit' do to engine displacement?

Accepted Answer

Increases displacement by using a longer crankshaft stroke

Answer

A stroker kit uses a crankshaft with increased stroke, moving the pistons farther up and down to displace more volume each cycle.

Question 4

In a turbocharged engine, what is 'compressor surge' and when does it typically occur?

Accepted Answer

Reverse airflow through the compressor when throttle closes suddenly under boost

Answer

Compressor surge occurs when boosted air has nowhere to go after throttle closure, reversing flow through the compressor and causing a characteristic flutter.

Question 5

What is the function of a Variable Valve Timing (VVT) system?

Accepted Answer

To alter camshaft phasing to optimize valve timing across different RPM ranges

Answer

VVT systems advance or retard camshaft position to optimize valve opening and closing events for both low-RPM torque and high-RPM power.

Car Tuning Practice Test

Car Tuning Practice Test

Car Tuning Engine Performance Principles 3