Video summary

Звук Двигателя! И как его изменить!

Main summary

Key takeaways

Educational

Main Ideas / Concepts Taught

  • Engine sound is physical, not just emotional/taste-based

    • People may prefer certain engine notes (e.g., “throaty roar,” “strained muscle pull”), but the video argues that the audible sound of an engine is determined by physics/mathematics.
    • Sound depends on:
      • Dominant frequency (the main “note” perceived)
      • Orders (repeat-rate categories tied to how many combustion events occur per crankshaft revolution)
      • Harmonics (additional frequency components that color the sound)
      • Engine configuration (number of cylinders, ignition timing, exhaust/transforming effects)
      • Operating speed (RPM) and load

  • What sound is (basic acoustics)

    • Sound is air-pressure disturbances caused by vibrations.
    • A wave has:
      • Amplitude (loudness-related, wave “height”)
      • Frequency (how many disturbances per unit time; higher frequency → higher pitch)
    • Microphones/electronics can reproduce the same pressure-wave pattern for speakers.

  • RPM → frequency mapping (how pitch changes with revs)

    • The video uses piano-keyboard analogies: higher RPM → higher frequency.
    • It notes engines contain many frequencies, but focuses on the fundamental/dominant tone shaped by engine “order” behavior.

Methodology: Determining “Order” and Dominant Frequency

The core calculation logic is:

  1. Step 1: Convert RPM to base rotation frequency

    • Rotation frequency (Hz) = RPM / 60

  2. Step 2: Determine how many “events” happen per crankshaft revolution

    • For a four-stroke engine, the complete thermodynamic cycle takes 2 crankshaft revolutions.
    • Therefore, for common cylinder counts, the number of ignitions (“flashes”) per one crankshaft revolution is:
      • V6 / inline-6: 3 flashes per crank revolution
      • 4-cylinder: 2 flashes per crank revolution
      • 8-cylinder: 4 flashes per crank revolution
      • 10-cylinder: 5 flashes per crank revolution
      • 12-cylinder: 6 flashes per crank revolution
    • In general framing:
      • Engine order = (flashes per crank revolution)
      • The video treats these as “third-order,” “second-order,” etc., repeatedly.

  3. Step 3: Dominant frequency from rotation frequency

    • Dominant frequency ≈ (rotation frequency) × (order number of events per crank revolution)
    • Example (worked in subtitles):
      • V6 at 1800 rpm
      • Rotation frequency = 1800 / 60 = 30 Hz
      • V6 fires 3 times per crank revolution
      • Dominant frequency = 30 Hz × 3 = 90 Hz
    • Even as revs increase, the engine still has the same number of flashes per crank revolution, so the dominant frequency scales with RPM while “order” stays constant.

  4. Step 4: Why “order” stays constant even if RPM doubles

    • The video uses gear/fan analogies:
      • Doubling RPM doubles frequency, but the “order” (e.g., “teeth per revolution” or “blade hits per revolution”) remains the same.
    • Therefore, order determines the recurring harmonic structure.

Core Lessons: How Engine “Color” Is Created

  • Order and dominant frequency shape harmonics

    • The dominant frequency sets where the main “note” begins.
    • Harmonics appear as multiples of that base note.
    • Higher order changes harmonic spacing/structure → different perceived timbre.

  • “Engine chord” analogy

    • The final sound is described as a combination of frequencies (a chord) made from:
      • dominant frequency
      • its harmonics
      • how they vary with RPM/load
    • This helps explain why sounds can be pleasant or unpleasant to different people.

  • Why manufacturers can make one engine sound like another

    • Example: Inline six sounding like a V8
      • The video claims an NVH-style system can shift the dominant component:
        • Inline-6 dominant frequency ~ 90 Hz
        • shifted to ~ 120 Hz, resembling an 8-cylinder (V8) dominant structure
      • Result: the driver experiences “V8-like” sound from a six-cylinder.
    • The video argues this can fool the brain because humans are sensitive to harmonic/dominant-frequency structures.

How Cylinder Count Changes the Harmonic Profile

  • Harmonics: frequency vs density

    • The video contrasts:
      • Small/two-stroke or high-rev small engines
        • more frequent harmonics (many components close together in spectral terms)
      • Large multi-cylinder engines (e.g., V8)
        • fewer repetitions/orders
        • but the existing orders start at higher amplitude/high-frequency components, described like a “hammer blow” character

  • Specific examples used

    • M52 (6-cylinder) vs LS V8
      • M52 base order = 3
      • V8 base order = 4
      • Illustrative dominant-related component series:
        • 6-cylinder:
          • low-speed: ~30/60/90 Hz
          • higher RPM: ~300/600/900 Hz
        • V8:
          • low-speed: ~40/80/120 Hz
          • higher RPM: ~400/800/1200 Hz
      • Since these frequency sets don’t align, the engines sound different.

NVH and Who Is Responsible for Tuning

  • NVH engineer
    • The video states factories use a dedicated Noise, Vibration, Hardness (NVH) engineer.
    • This includes managing the sonic output (and, in modern practice, potentially using sound systems/transformations).

Disclaimers / Transition: Exhaust System (Preview)

  • The video says it won’t fully cover the exhaust system yet, since it would require a separate long video.
  • It does explain that exhaust acts as a bridge to the ears and will later be discussed as an “instrument” that transforms the produced harmonic content.

Separate Segment: Choosing Brake-Compatible Wheels (Skill Wheels)

Goal

  • Correctly measure a brake setup before buying wheels to avoid:
    • caliper-to-spoke collisions
    • insufficient clearance after wheel deformation
    • overheating consequences (heat transfer to tire)

Tools Needed

  • Ruler
  • Calipers
  • Tape measure
  • Free time and careful measurement

General Clearance Rules

  • Always choose sizes with margin
    • Wheels deform under load; deformation may not be visually obvious.
    • Reserve is needed so calipers won’t contact spokes.
  • Outside wheel in cornering bears higher load → more deformation.
  • Forged/magnesium wheels
    • may deform more, but (the video claims) forged wheels return toward original shape.

Wheel Rim Designations / Fit Systems (as described)

  • Ads like “discs such and such” relate to wheel spoke geometry.
  • Systems mentioned:
    • Brem/BrMO (as named in subtitles)
    • Z17 / Z18 denote minimum wheel rim diameter compatible with a brake system:
      • Z17 → min 17 inches
      • Z18 → min 18 inches

Dimensions to Measure (A–J list)

Using a brake system example for a Nissan Skyline R34 (branded in subtitles as “Bremo”), the described measurements are:

  • A: distance from hub center to the relevant edge/face of the brake caliper (to avoid spoke collision)
    • Example: 180 mm
  • B: distance from wheel rim axis center to an edge of the caliper
    • Example: 120 mm
    • Used to evaluate wheel/spoke clearance—especially when brakes are smaller and spokes may interfere.
  • C: distance from hub center to the very far edge of the caliper
    • Initially example: 180 mm
    • But measured farther edge: 200 mm
    • Instruction: measure the farthest corners to prevent wheel rim collision with protruding caliper parts.
  • D: distance from hub center to another caliper edge
    • Why: different brake discs have different widths on the adjacent mounting plane; width can interfere with smaller brake setups
    • Example: 115 mm
  • E: distance from caliper plane to wheel disc mounting plane (reserve for correct wheel offset)
    • Example: 40 mm
    • Purpose: ensure correct offset so the wheel does not contact the brake caliper/spokes.
  • F: hub protrusion distance from the brake disc
    • Example: 5 mm
  • J: brake disc offset (mounting-plane separation from working plane)
    • Example: 14 mm

Outcome Benefits

  • Avoid wasting money/time on wrong wheels.
  • Ensure brake and wheel work together properly.

Heat / Tire Warning

  • Even if mechanical clearance exists, overheating can still happen if:
    • wheel size is too small
    • brake clearance is too tight
    • wheel rim overheats from brake heat
  • Heat then transfers to the tire, risking overheating and related problems.
  • Therefore, selection must consider thermal consequences too.

Speaker / Source List (as Referenced in Subtitles)

  • Klepachevsky (host/presenter throughout)
  • “Skill Wheels” (referenced as a brand/help resource for wheel selection)
  • Named engine manufacturers/brands referenced as examples (not speakers):
    • Ferrari, Porsche, Honda, Toyota, Yamaha, Lexus (LFA), Mercedes AMG, Audi, Volkswagen
    • Harley-Davidson (engine example)
    • BMW (M52 referenced)
    • Chevrolet (LS V8 referenced)
  • No other distinct human speakers are identified in the subtitles.

Original video