ICE-43 — Engine NVH

ASSUMPTION — This lesson covers NVH conceptually; specific sound/dB values are not given.

In this lesson you will learn:

• The NVH concept
• Engine NVH sources
• Reduction methods

1. What Is NVH?

NVH stands for Noise, Vibration and Harshness. The engine is a source of all three through combustion and moving parts.

FACT — NVH is critical for comfort and perceived quality; some sounds can also signal faults (e.g., knock, bearing wear).

2. Sources

• Combustion — the sharp rise in cylinder pressure (combustion noise).
• Mechanical — piston slap, valvetrain, gears/chains.
• Imbalance — inertia forces of rotating/reciprocating masses.

FACT — Engine “orders” are expressed as multiples of crank speed (e.g., 2nd order in a 4-cylinder). Balancer shafts and counterweights reduce these forces.

3. Reduction Methods

FACT — NVH is reduced via balancer shafts, engine mounts, block stiffness, muffler design and calibration (injection/ignition strategy). Pilot injection is effective for combustion noise in diesels.

4. Summary

• NVH = noise + vibration + harshness.
• Sources: combustion, mechanical, imbalance.
• Reduced via balancers, mounts and calibration.

5. Sources

• Heywood, Internal Combustion Engine Fundamentals
• Bosch Automotive Handbook

Next Lesson

• ICE-44 — Engine Durability.