'Vibratto' effect in the engine sound

[modbaraban]

Many GT cars have this vibratto* effect usually on low revs or at low speeds.

Here's what I'm tlking about (0:30 while taking the last turn):
[youtube]http://www.youtube.com/watch?v=jLELrQUTE1w[/youtube]

And plenty of that here: http://gt1live.tv/index.html
You can hear that from fast revving V12s, Chevy V8 or Ferrari V8s, V10s, pretty much any kind of engine.


What causes this effect and why don't we usually hear that in most cars of other types (single-seaters, touring, roadcars etc.)?

________________________
*Vibrato is a musical effect, produced in singing and on musical instruments by a regular pulsating change of pitch, and is used to add expression.

[mrk189]

thats the straightcut gearbox, not the engine.

[modbaraban]

That doesn't sound like gearbox whine. You can hear that clearly with low pitched engines like the LS7 V8. Its pitch vibrates at low revs while exiting slow corners and and similar effect happens after every downshift.
[youtube]http://www.youtube.com/watch?v=BCjk2cx8fl8[/youtube]

[Scotracer]

At low speeds you are in a lower gear therefore any prod on the throttle or overrun causes more load through the gearbox (torque translated via the gear ratios) and it causes it to be more pronounced and jitter - with the jitter, axle-tramp plays a role in it. Although small, since you have a straight-cut gearbox you can hear it distinctly. Also, since racing engines have small/no flywheel they lose inertia fast so the actual piston compression strokes are more noticeable and add to it.


It is noticeable in my every day car (Integra Type R) when in first or 2nd gear where you have a massive gear-ratio. You don't hear it in regular road cars because they have a lot of sound deadening (my Integra has zero, as it came out the factory from Honda). With F1 cars the exhausts are so loud that you would never hear it over the engine. You can hear it with lower Formula such as Formula Ford and F3. Touring cars...it is audible but only in brief amounts (V8 Supercars do it quite a lot actually).

[modbaraban]

Thanks. That sounds like it. And yes, I forgot to mention the aussie V8s.

[ESPImperium]

In music Vibrato often gets confused with Tremolo, and vice versa.

What im saying here, is that i think that the revs are getting bodded down and thus producing a tremolo effect to me as the rear settles, the endine settles, thus producing a tremolo effect and not a vibrato.

[modbaraban]

No I actually meant pitch (rpm) variations, thus vibratto and not tremolo.

[Saribro]

I guess ESPImperium got confused by his own post :).

[timbo]

Maybe they blip the throttle much? That was once very common for F1 drivers (esp. in turbo days), listen to the sound on Senna's onboard videos - he used this technique quite a lot.

[modbaraban]

Maybe they blip the throttle much? That was once very common for F1 drivers (esp. in turbo days), listen to the sound on Senna's onboard videos - he used this technique quite a lot.

I don't think any human being can blip the throttle with that frequency, cuz sometimes it's a very fast vibratto.

A perfect example right at the beginning (while accelerating at the pitlane exit).
[youtube]http://www.youtube.com/watch?v=cOTOoW126no[/youtube]

[timbo]

I don't think any human being can blip the throttle with that frequency, cuz sometimes it's a very fast vibratto.

I hear you, but Senna was actually VERY fast. Hakkinen did that too watch here near the end http://www.youtube.com/watch?v=iN--nd8Lg84

But I agree that the cause is probably something else. My theory would be that the huge torque of GT engines (as they have much higher displacement than F1 engines) cause huge low-frequency vibrations at low-revs and when driver is gentle with the throttle it would cause that his action on the pedal would be modulated with the frequemcy of that vibration.

[Callum]

Are you sure it's not just traction control??

[Scotracer]

Maybe they blip the throttle much? That was once very common for F1 drivers (esp. in turbo days), listen to the sound on Senna's onboard videos - he used this technique quite a lot.

I don't think any human being can blip the throttle with that frequency, cuz sometimes it's a very fast vibratto.

A perfect example right at the beginning (while accelerating at the pitlane exit).
[youtube]http://www.youtube.com/watch?v=cOTOoW126no[/youtube]

That's just the fact the cars have no flywheel and very high-overlap cams so they don't run well at the bottom end of the revs.