CPT CPT Data Analysis & Interpretation

Question 1

When analyzing a dyno chart, a flat torque curve across a wide RPM range typically indicates what about the engine's tuning?

Accepted Answer

Optimal volumetric efficiency across the RPM band

Answer

Excessive ignition advance

Answer

A clogged fuel injector

Answer

Overheating coolant system

Question 2

On a wideband oxygen sensor data log, an AFR reading consistently above 15.0:1 at wide open throttle (WOT) indicates which condition?

Accepted Answer

Lean mixture

Answer

Rich mixture

Answer

Stoichiometric combustion

Answer

Optimal power mixture

Question 3

What does a sudden spike in short-term fuel trim (STFT) values to +25% indicate in a performance diagnostic?

Accepted Answer

The ECU is adding fuel to compensate for a lean condition

Answer

Excessive fuel pressure

Answer

A rich exhaust condition

Answer

Normal closed-loop operation

Question 4

Which data parameter is MOST useful for identifying knock (detonation) events during performance testing?

Accepted Answer

Knock sensor retard counts or ignition timing pull

Answer

MAP sensor voltage

Answer

Coolant temperature PID

Answer

Throttle position percentage

Question 5

A technician reviews data logs and sees that volumetric efficiency (VE) drops sharply above 5,500 RPM. What is the most likely cause?

Accepted Answer

Cam phaser malfunction limiting intake duration at high RPM

Answer

Throttle position sensor failure

Answer

Low battery voltage

Answer

Incorrect tire pressure

Question 6

When interpreting an oscilloscope waveform of an injector signal, what does a longer pulse width (ms) indicate?

Accepted Answer

Greater fuel delivery to the cylinder

Answer

Lower fuel demand

Answer

A lean fuel mixture

Answer

Reduced injector duty cycle