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Engine Performance & Tuning Flashcards

7 cards from real CTE practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Engine Performance & Tuning flashcards as text

  1. What is the stoichiometric air-fuel ratio (AFR) for gasoline combustion?

    Answer: 14.7:1

    14.7:1 is the stoichiometric ratio where all fuel and air are theoretically consumed, yielding the best catalyst efficiency.

  2. Which ignition system component stores and releases the high-voltage energy needed to fire a spark plug?

    Answer: Ignition coil

    The ignition coil transforms battery voltage into the high voltage (20,000–40,000+ V) required to jump the spark plug gap.

  3. A student notices that spark plug electrodes are coated with black, sooty carbon deposits. This condition indicates:

    Answer: Rich combustion or excessive oil burning

    Black carbon fouling results from an overly rich mixture or oil entering the combustion chamber being incompletely burned.

  4. What does base ignition timing refer to in engine tuning?

    Answer: The fixed timing set when the ECU advance is disabled or disconnected

    Base timing is the initial timing reference set mechanically or by the ECU base map before dynamic advance is applied.

  5. Variable valve timing (VVT) systems improve engine performance primarily by:

    Answer: Optimizing valve opening and closing events across the RPM range

    VVT adjusts camshaft phasing to optimize power and efficiency at both low and high RPM operating conditions.

  6. A student is testing engine compression. Cylinder pressures are 175, 170, 172, and 95 psi. The best next diagnostic step is:

    Answer: Perform a wet compression test on the low cylinder

    Adding oil to the low cylinder for a wet compression test distinguishes between worn rings (pressure rises) and valve or head gasket issues (pressure stays low).

  7. When using an oscilloscope to analyze a crankshaft position (CKP) sensor signal, a missing tooth in the waveform pattern would indicate:

    Answer: The timing reference point on the reluctor wheel

    Most CKP reluctor wheels have a missing tooth to provide the ECU with a precise TDC reference point for timing calculations.