Car Tuning Forced Induction Systems 3

Question 1

What is the primary purpose of an oil return line on a turbocharger?

Accepted Answer

Drain oil from the turbo center housing back to the engine sump by gravity

Answer

The oil return (drain) line relies on gravity to drain oil from the turbo center section back to the oil pan, so it must never be kinked or run uphill.

Question 2

Which forced induction method produces peak boost at lower RPM without turbo lag?

Accepted Answer

Positive displacement supercharger

Answer

Positive displacement superchargers (Roots or twin-screw) are belt-driven and produce boost proportional to engine speed, delivering strong low-RPM response.

Question 3

What does 'intercooler efficiency' measure?

Accepted Answer

How effectively the intercooler reduces charge air temperature relative to maximum possible cooling

Answer

Intercooler efficiency is the ratio of actual temperature reduction to the maximum possible reduction (inlet air temp minus ambient temp), expressed as a percentage.

Question 4

Why do many high-boost setups use a water-methanol injection system?

Accepted Answer

To increase fuel octane rating and reduce intake charge temperature simultaneously

Answer

Water-methanol injection cools the intake charge through evaporation and raises the effective octane rating, allowing more timing advance and boost without detonation.

Question 5

On a turbocharged engine, what does a higher A/R (area-to-radius) ratio turbine housing produce?

Accepted Answer

Higher peak power at elevated RPM with increased top-end flow capacity

Answer

A higher turbine A/R housing reduces exhaust velocity and backpressure at high RPM, supporting greater airflow and peak power but at the cost of slower spool-up.

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Car Tuning Forced Induction Systems 3