Buzzy Blarp Sound when Engine Braking

[Jinba ittai]

Who is hearing a buzzy blarp sound under engine braking? Could also be described as a half second fog horn sound. Anyone know what it is?

 

[Jinba ittai]

To be clear engine is braking not breaking. Don’t know if I can edit the title at this point.

 

[NJemira85]

To be clear engine is braking not breaking. Don’t know if I can edit the title at this point.

This is an unfortunate typo.

@Porter maybe can fix ? Idk the other mods

 

[Kimmax]

Copying my answer from the other thread:

Yes! Since factory. No one came up with an explanation yet and I fear it's the clutch.
I have one month left for warranty and I swear to god if the clutch goes next year I'm driving up to Hethel (if someone is left there by then..)

 

[Kimmax]

A theory I came up with, no idea if mechanically sound:

It almost sounds like the clutch slips as it starts to accelerate the engine to match the gearbox. I get this sound primarily when I don’t rev match properly when down shifting. With rev match I haven’t ever heard this. I cannot force it to happen however, so I couldn’t show it to the mechanic yet.

Now that I'm writing this I'm not sure if the sound emits while the clutch pedal comes up or even after the clutch is fully engaged.
If it’s in the transition phase it might actually just be the clutch slipping, whether it should sound like that or not I'm not sure

 

[Jinba ittai]

A theory I came up with, no idea if mechanically sound:

It almost sounds like the clutch slips as it starts to accelerate the engine to match the gearbox. I get this sound primarily when I don’t rev match properly when down shifting. With rev match I haven’t ever heard this. I cannot force it to happen however, so I couldn’t show it to the mechanic yet.

Now that I'm writing this I'm not sure if the sound emits while the clutch pedal comes up or even after the clutch is fully engaged.
If it’s in the transition phase it might actually just be the clutch slipping, whether it should sound like that or not I'm not sure

I think you’re right that it’s clutch related as it happens for me on downshift. If it’s the sound of the clutch slipping it’s unlike any other slipping clutch I’ve ever heard. Seems like the vibration is at just the right frequency to cause intense resonance on something.

 

[VL3X]

This is an unfortunate typo.

@Porter maybe can fix ? Idk the other mods

I got it (and you should know me).

 

[Rupes]

Also copying my response from the other thread - hopefully provides some additional context: It's especially noticeable to for me at low speeds / low rpms while decelerating, maybe because the engine isn't loud enough to cover up the sound.

Sounds like a buzzy blarp sound, lol. How's that for a description?

 

[Jinba ittai]

I was initially relieved that this may be a common thing. However, it might just be the three of us…. I will continue to monitor and hope it’s nothing. Maybe work on better rev matching.

 

[geoffbland]

I believe I have heard something like this too but very infrequently. Only happens for a very short while, at low speed and low revs under a bit of engine braking. Also seems to only be when I am first setting off - so when the engine is cold. I thought it might just be the rear brake pads rattling a bit as the engine judders under engine braking.

 

[Kimmax]

I listend a bit closer today and it only sounds while the clutch is slipping as your release the pedal
- NOT deliberately slipping, but one usual smooth clutch application -
Im also kind of able to reproduce it if I downshift without rev matching from 3rd to 2nd, but it's only very quiet.

Without rev-match the engine rpm is too low compared to the transmission input speed set by road speed and the new lower gear. As the clutch is released, the transmission drags the engine up to match. That rapid slip phase is where the foghorn sound comes in

Engine braking only kicks in once engine and transmission speeds are in sync. During the transition, the rpm difference is handled by clutch slip. Some energy goes into spinning the engine up, the rest is wasted as heat in the friction material.

That explains the origin, but I’m still not sure if it’s "normal" for it to sound like this. Obviously you shouldn’t be in that situation if you rev-match properly, but even if you mess it up, it’s not clear whether a factory-fresh clutch should make noise.

That said, I’m at 38,000 km and the clutch still works fine. I only hear it when I screw up, so hopefully it’s just a "thing" and not a sign the clutch is going to peace out early lol

Maybe @Porter has something to say about this, he seems to know a thing or two

 

[Jinba ittai]

38000 km? Well done. That gives me some peace.